Patent Publication Number: US-11644911-B2

Title: Button functionality

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/378,451, entitled “BUTTON FUNCTIONALITY,” filed Jul. 16, 2021, which is a continuation of U.S. patent application Ser. No. 16/384,726, now U.S. Pat. No. 11,068,083, entitled “BUTTON FUNCTIONALITY,” filed Apr. 15, 2019, which is a continuation of U.S. patent application Ser. No. 16/055,489, now U.S. Pat. No. 10,281,999, entitled “BUTTON FUNCTIONALITY,” filed Aug. 6, 2018, which is a continuation of U.S. patent application Ser. No. 14/641,252, now U.S. Pat. No. 10,082,892, entitled “BUTTON FUNCTIONALITY,” filed Mar. 6, 2015, which claims priority to U.S. Provisional Patent Application No. 62/044,922, entitled “BUTTON FUNCTIONALITY,” filed Sep. 2, 2014, the contents of each of which are hereby incorporated by reference in their entireties. 
     This application relates to the following applications: International Patent Application Serial No. PCT/US2013/040087, entitled “Device, Method, and Graphical User Interface for Moving a User Interface Object Based on an Intensity of a Press Input,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040072, entitled “Device, Method, and Graphical User Interface for Providing Feedback for Changing Activation States of a User Interface Object,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040070, entitled “Device, Method, and Graphical User Interface for Providing Tactile Feedback for Operations Performed in a User Interface,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040067, entitled “Device, Method, and Graphical User Interface for Facilitating User Interaction with Controls in a User Interface,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040061, entitled “Device, Method, and Graphical User Interface for Displaying User Interface Objects Corresponding to an Application,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040058, entitled “Device, Method, and Graphical User Interface for Displaying Additional Information in Response to a User Contact,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040056, entitled “Device, Method, and Graphical User Interface for Scrolling Nested Regions,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040054, entitled “Device, Method, and Graphical User Interface for Manipulating Framed Graphical Objects,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/069489, entitled “Device, Method, and Graphical User Interface for Switching Between User Interfaces,” filed Nov. 11, 2013; International Patent Application Serial No. PCT/US2013/069486, entitled “Device, Method, and Graphical User Interface for Determining Whether to Scroll or Select Content,” filed Nov. 11, 2013; International Patent Application Serial No. PCT/US2013/069484, entitled “Device, Method, and Graphical User Interface for Moving a Cursor According to a Change in an Appearance of a Control Icon with Simulated Three-Dimensional Characteristics,” filed Nov. 11, 2013; International Patent Application Serial No. PCT/US2013/069483, entitled “Device, Method, and Graphical User Interface for Transitioning Between Touch Input to Display Output Relationships,” filed Nov. 11, 2013; International Patent Application Serial No. PCT/US2013/069479, entitled “Device, Method, and Graphical User Interface for Forgoing Generation of Tactile Output for a Multi-Contact Gesture,” filed Nov. 11, 2013; International Patent Application Serial No. PCT/US2013/069472, entitled “Device, Method, and Graphical User Interface for Navigating User Interface Hierarchies,” filed Nov. 11, 2013; International Patent Application Serial No. PCT/US2013/040108, entitled “Device, Method, and Graphical User Interface for Moving and Dropping a User Interface Object,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040101, entitled “Device, Method, and Graphical User Interface for Selecting User Interface Objects,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040098, entitled “Device, Method, and Graphical User Interface for Displaying Content Associated with a Corresponding Affordance,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040093, entitled “Device, Method, and Graphical User Interface for Transitioning Between Display States in Response to a Gesture,” filed May 8, 2013; International Patent Application Serial No. PCT/US2013/040053, entitled “Device, Method, and Graphical User Interface for Selecting Object within a Group of Objects,” filed May 8, 2013; U.S. Patent Application Ser. No. 61/778,211, entitled “Device, Method, and Graphical User Interface for Facilitating User Interaction with Controls in a User Interface,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,191, entitled “Device, Method, and Graphical User Interface for Displaying User Interface Objects Corresponding to an Application,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,171, entitled “Device, Method, and Graphical User Interface for Displaying Additional Information in Response to a User Contact,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,179, entitled “Device, Method and Graphical User Interface for Scrolling Nested Regions,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,156, entitled “Device, Method, and Graphical User Interface for Manipulating Framed Graphical Objects,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,125, entitled “Device, Method, And Graphical User Interface for Navigating User Interface Hierarchies,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,092, entitled “Device, Method, and Graphical User Interface for Selecting Object Within a Group of Objects,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,418, entitled “Device, Method, and Graphical User Interface for Switching Between User Interfaces,” filed Mar. 13, 2013; U.S. Patent Application Ser. No. 61/778,416, entitled “Device, Method, and Graphical User Interface for Determining Whether to Scroll or Select Content,” filed Mar. 13, 2013; U.S. Patent Application Ser. No. 61/747,278, entitled “Device, Method, and Graphical User Interface for Manipulating User Interface Objects with Visual and/or Haptic Feedback,” filed Dec. 29, 2012; U.S. Patent Application Ser. No. 61/778,414, entitled “Device, Method, and Graphical User Interface for Moving and Dropping a User Interface Object,” filed Mar. 13, 2013; U.S. Patent Application Ser. No. 61/778,413, entitled “Device, Method, and Graphical User Interface for Selecting User Interface Objects,” filed Mar. 13, 2013; U.S. Patent Application Ser. No. 61/778,412, entitled “Device, Method, and Graphical User Interface for Displaying Content Associated with a Corresponding Affordance,” filed Mar. 13, 2013; U.S. Patent Application Ser. No. 61/778,373, entitled “Device, Method, and Graphical User Interface for Managing Activation of a Control Based on Contact Intensity,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,265, entitled “Device, Method, and Graphical User Interface for Transitioning Between Display States in Response to a Gesture,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,367, entitled “Device, Method, and Graphical User Interface for Moving a User Interface Object Based on an Intensity of a Press Input,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,363, entitled “Device, Method, and Graphical User Interface for Transitioning Between Touch Input to Display Output Relationships,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,287, entitled “Device, Method, and Graphical User Interface for Providing Feedback for Changing Activation States of a User Interface Object,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,284, entitled “Device, Method, and Graphical User Interface for Providing Tactile Feedback for Operations Performed in a User Interface,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/778,239, entitled “Device, Method, and Graphical User Interface for Forgoing Generation of Tactile Output for a Multi-Contact Gesture,” filed Mar. 12, 2013; U.S. Patent Application Ser. No. 61/688,227, entitled “Device, Method, and Graphical User Interface for Manipulating User Interface Objects with Visual and/or Haptic Feedback,” filed May 9, 2012; U.S. Provisional Patent Application Ser. No. 61/645,033, filed on May 9, 2012, entitled “Adaptive Haptic Feedback for Electronic Devices;” U.S. Provisional Patent Application Ser. No. 61/665,603, filed on Jun. 28, 2012, entitled “Adaptive Haptic Feedback for Electronic Devices;” U.S. Provisional Patent Application Ser. No. 61/681,098, filed on Aug. 8, 2012, entitled “Adaptive Haptic Feedback for Electronic Devices;” U.S. Utility application Ser. No. 12/987,982, filed Jan. 10, 2011, entitled “Intelligent Automated Assistant;” and U.S. Provisional Patent Application Ser. No. 62/004,886, filed May 29, 2014, entitled “User Interface for Payments”. The content of these applications is hereby incorporated by reference in their entirety. 
    
    
     FIELD 
     The present disclosure relates generally to computer user interfaces, and more specifically to button functionalities for user interfaces. 
     BACKGROUND 
     Users rely on portable multifunction devices for a variety of operations, such as communicating with friends, accessing and displaying information, and running software applications. A user may wish to invoke user interfaces for these operations in a quick and convenient way. It is desirable for the user interface for invoking operations to be intuitive and comprehensible to a user. As electronics packaging techniques improve, smaller and more portable devices are made, which further challenges computer user interface designers by reducing the available real estate to display affordances, user interface objects, and icons for accessing various user interfaces. 
     SUMMARY 
     It is desirable to provide user access to numerous user interfaces in a way that is intuitive and comprehensible to a user. Therefore, multifunctional button functionalities for portable multifunction devices are increasingly desirable for providing access to user interfaces. 
     In some embodiments, a method of providing button functionalities for user interfaces comprises: at an electronic device with a display and a rotatable and depressible input mechanism: receiving data representing an activation of the rotatable and depressible input mechanism, the activation having an associated activation duration; determining whether the activation duration exceeds a predetermined threshold; determining a state of an active application; and in accordance with a determination that the activation duration exceeds the predetermined threshold, and in accordance with a determination of the state of the active application: performing an action. 
     In some embodiments, a method of providing button functionalities for user interfaces comprises: at an electronic device with a display and a rotatable and depressible input mechanism: receiving data representing an activation of the rotatable and depressible input mechanism, the activation having an associated activation duration; determining whether the activation duration exceeds a predetermined threshold; in accordance with a determination that the activation duration does not exceed the predetermined threshold: displaying a first user interface screen on the display, the first user interface screen including a plurality of affordances, the plurality of affordances comprising an affordance representing an application; while the first user interface screen is displayed, receiving second data representing a second activation of the rotatable and depressible input mechanism, the second activation having an associated second activation duration; determining whether the second activation duration exceeds a second predetermined threshold; and in accordance with a determination that the second activation duration does not exceed the second predetermined threshold: substituting the display of the first user interface screen with a display of a second user interface screen, the second user interface screen including a clock face. 
     In some embodiments, a method of providing button functionalities for user interfaces comprises: at an electronic device with a display and a rotatable and depressible input mechanism: receiving first data representing a first activation of the rotatable and depressible input mechanism and a second activation of the rotatable and depressible input mechanism, the first and the second activations having an associated interval between the first and the second activations; in response to receiving the first data, determining whether the interval between the first and the second activations exceeds a predetermined threshold; and in accordance with a determination that the interval does not exceed the predetermined threshold: invoking a previously invoked application. 
     In some embodiments, a method of providing button functionalities for user interfaces comprises: at an electronic device with a touch-sensitive display, a button, and a rotatable and depressible input mechanism: receiving first data representing an activation of the button, the activation having an associated activation duration; determining whether the activation duration exceeds a predetermined threshold; and in accordance with a determination that the activation duration does not exceed the predetermined threshold: displaying a user interface screen, the user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, wherein the designated list is a subset of a full list of contacts on the electronic device. 
     In some embodiments, a method of providing button functionalities for user interfaces comprises: at an electronic device with a touch-sensitive display, a button, and a rotatable and depressible input mechanism: receiving first data representing a first activation of the button and a second activation of the button, the first and the second activations having an associated interval between the first and the second activations; determining whether the interval between the first and the second activations exceeds a predetermined threshold; and in accordance with a determination that the interval does not exceed the predetermined threshold: invoking a payments application. 
     In some embodiments, a method of providing button functionalities for user interfaces comprises: at an electronic device with a display, a button, and a rotatable and depressible input mechanism: receiving data representing an activation of the button and an activation of the rotatable and depressible input mechanism, wherein the activation of the button has a first associated activation duration, wherein the activation of the rotatable and depressible input mechanism has a second associated activation duration and overlaps with the activation of the button for an overlap interval, and wherein the activation of the button and the activation of the rotatable and depressible input mechanism are received substantially simultaneously; determining whether the data meet predetermined criteria; and in accordance with a determination that the data meet the predetermined criteria: rebooting the electronic device. 
     In some embodiments, a method of providing button functionalities for user interfaces comprises: at an electronic device with a display, a rotatable and depressible input mechanism and a button: receiving first data representing an activation of the rotatable and depressible input mechanism; determining whether the activation represents: a single press of the rotatable and depressible input mechanism, the single press having an associated press duration; a double press of the rotatable and depressible input mechanism, the double press having an associated interval between a first press of the rotatable and depressible input mechanism and a second press of the rotatable and depressible input mechanism, the first and the second presses of the rotatable and depressible input mechanism each having an associated press duration; or an extended press of the rotatable and depressible input mechanism, the extended press having an associated press duration; and in accordance with a determination that the activation represents a single press of the rotatable and depressible input mechanism: displaying a first user interface screen on the display, the first user interface screen including a plurality of affordances, the plurality of affordances comprising an affordance representing an application; in accordance with a determination that the activation represents a double press of the rotatable and depressible input mechanism: invoking a previously invoked application; and in accordance with a determination that the activation represents an extended press of the rotatable and depressible input mechanism: determining a state of an active application; and in accordance with a determination of the state of the active application: performing an action. 
     In some embodiments, a method of providing button functionalities for user interfaces comprises: at an electronic device with a display, a rotatable and depressible input mechanism and a button: receiving first data representing an activation of the button; determining whether the activation represents: a single press of the button, the single press having an associated press duration; a double press of the button, the double press having an associated interval between a first consecutive press and a second consecutive press, the first and second consecutive presses each having an associated press duration; or an extended press of the button, the extended press having an associated press duration; and in accordance with a determination that the activation represents a single press of the button: displaying a first user interface screen, the first user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, wherein the designated list is a subset of a full list of contacts on the electronic device; in accordance with a determination that the activation represents a double press of the button: invoking a payments application; and in accordance with a determination that the activation represents an extended press of the button: displaying a second user interface screen, the second user interface screen comprising a second affordance representing a user prompt to power off the electronic device. 
     In some embodiments, a device comprises means for receiving data representing an activation of a rotatable and depressible input mechanism, the activation having an associated activation duration; means for determining whether the activation duration exceeds a predetermined threshold; means for determining a state of an active application; and means for performing an action in accordance with a determination that the activation duration exceeds the predetermined threshold and in accordance with a determination of the state of the active application. 
     In some embodiments, a device comprises means for receiving data representing an activation of a rotatable and depressible input mechanism, the activation having an associated activation duration; means for displaying a first user interface screen, the first user interface screen including a plurality of affordances, the plurality of affordances comprising an affordance representing an application in accordance with a determination that the activation duration does not exceed the predetermined threshold; means for receiving second data representing a second activation of the rotatable and depressible input mechanism, the second activation having an associated second activation duration; means for determining whether the second activation duration exceeds a second predetermined threshold; and means for substituting the display of the first user interface screen with a display of a second user interface screen, the second user interface screen including a clock face, in accordance with a determination that the second activation duration does not exceed the second predetermined threshold. 
     In some embodiments, a device comprises means for receiving first data representing a first activation of a rotatable and depressible input mechanism and a second activation of the rotatable and depressible input mechanism, the first and the second activations having an associated interval between the first and the second activations; means responsive to receiving the first data for determining whether the interval between the first and the second activations exceeds a predetermined threshold; and means for invoking a previously invoked application in accordance with a determination that the interval does not exceed the predetermined threshold. 
     In some embodiments, a device comprises means for receiving first data representing an activation of a button, the activation having an associated activation duration; means for determining whether the activation duration exceeds a predetermined threshold; and means for displaying a user interface screen, the user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, wherein the designated list is a subset of a full list of contacts on the device in accordance with a determination that the activation duration does not exceed the predetermined threshold. 
     In some embodiments, a device comprises means for receiving first data representing a first activation of a button and a second activation of the button, the first and the second activations having an associated interval between the first and the second activations; means for determining whether the interval between the first and the second activations exceeds a predetermined threshold; and means for invoking a payments application in accordance with a determination that the interval does not exceed the predetermined threshold. 
     In some embodiments, a device comprises means for receiving data representing an activation of a button and an activation of a rotatable and depressible input mechanism, wherein the activation of the button has a first associated activation duration, wherein the activation of the rotatable and depressible input mechanism has a second associated activation duration and overlaps with the activation of the button for an overlap interval, and wherein the activation of the button and the activation of the rotatable and depressible input mechanism are received substantially simultaneously; means for determining whether the data meet predetermined criteria; and means for rebooting the device in accordance with a determination that the data meet the predetermined criteria. 
     In some embodiments, a device comprises means for receiving first data representing an activation of a rotatable and depressible input mechanism; means for determining whether the activation represents a single press of the rotatable and depressible input mechanism, a double press of the rotatable and depressible input mechanism, or an extended press of the rotatable and depressible input mechanism; means for displaying a first user interface screen, the first user interface screen including a plurality of affordances, the plurality of affordances comprising an affordance representing an application in accordance with a determination that the activation represents a single press of the rotatable and depressible input mechanism; means for invoking a previously invoked application in accordance with a determination that the activation represents a double press of the rotatable and depressible input mechanism; means for determining a state of an active application in accordance with a determination that the activation represents an extended press of the rotatable and depressible input mechanism; and means for performing an action in accordance with a determination of the state of the active application. 
     In some embodiments, a device comprises means for receiving first data representing an activation of a button; means for determining whether the activation represents a single press of the button, a double press of the button, or an extended press of the button; means for displaying a first user interface screen, the first user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, wherein the designated list is a subset of a full list of contacts on the device in accordance with a determination that the activation represents a single press of the button; means for invoking a payments application in accordance with a determination that the activation represents a double press of the button; and means for displaying a second user interface screen, the second user interface screen comprising a second affordance representing a user prompt to power off the device in accordance with a determination that the activation represents an extended press of the button. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       For a better understanding of the various described embodiments, reference should be made to the Description of Embodiments below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures. 
         FIG.  1 A  is a block diagram illustrating a portable multifunction device with a touch-sensitive display in accordance with some embodiments. 
         FIG.  1 B  is a block diagram illustrating exemplary components for event handling in accordance with some embodiments. 
         FIG.  2    illustrates a portable multifunction device having a touch-sensitive display in accordance with some embodiments. 
         FIG.  3    is a block diagram of an exemplary multifunction device with a display and a touch-sensitive surface in accordance with some embodiments. 
         FIG.  4 A  illustrates an exemplary user interface for a menu of applications on a portable multifunction device in accordance with some embodiments. 
         FIG.  4 B  illustrates an exemplary user interface for a multifunction device with a touch-sensitive surface that is separate from the display in accordance with some embodiments. 
         FIG.  5 A  illustrates a personal electronic device in accordance with some embodiments. 
         FIG.  5 B  is a block diagram illustrating a personal electronic device in accordance with some embodiments. 
         FIGS.  6 A and  6 B  illustrate exemplary button functionalities for user interfaces. 
         FIG.  7    illustrates exemplary button functionalities for user interfaces. 
         FIG.  8    illustrates exemplary button functionalities for user interfaces. 
         FIG.  9    illustrates exemplary button functionalities for user interfaces. 
         FIG.  10    illustrates exemplary button functionalities for user interfaces. 
         FIG.  11    illustrates exemplary button functionalities for user interfaces. 
         FIG.  12    illustrates exemplary button functionalities for user interfaces. 
         FIG.  13    is a flow diagram illustrating a process for button functionalities for user interfaces. 
         FIG.  14    is a flow diagram illustrating a process for button functionalities for user interfaces 
         FIG.  15    is a flow diagram illustrating a process for button functionalities for user interfaces. 
         FIG.  16    is a flow diagram illustrating a process for button functionalities for user interfaces. 
         FIG.  17    is a flow diagram illustrating a process for button functionalities for user interfaces. 
         FIG.  18    is a flow diagram illustrating a process for button functionalities for user interfaces. 
         FIG.  19    is a flow diagram illustrating a process for button functionalities for user interfaces. 
         FIG.  20    is a flow diagram illustrating a process for button functionalities for user interfaces. 
         FIG.  21    is a functional block diagram of an electronic device in accordance with some embodiments. 
         FIG.  22    is a functional block diagram of an electronic device in accordance with some embodiments. 
         FIG.  23    is a functional block diagram of an electronic device in accordance with some embodiments. 
         FIG.  24    is a functional block diagram of an electronic device in accordance with some embodiments. 
         FIG.  25    is a functional block diagram of an electronic device in accordance with some embodiments. 
         FIG.  26    is a functional block diagram of an electronic device in accordance with some embodiments. 
         FIG.  27    is a functional block diagram of an electronic device in accordance with some embodiments. 
         FIG.  28    is a functional block diagram of an electronic device in accordance with some embodiments. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following description sets forth exemplary methods, parameters and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure but is instead provided as a description of exemplary embodiments. 
     As discussed above, a user may wish to access various user interfaces for using different functions on a portable multifunction device. Providing functionalities for accessing such user interfaces without relying solely on displayed icons may be beneficial for multifunction devices of any size by freeing the display for other features or aspects. Other input mechanisms such as buttons may these additional functionalities, but it is highly desirable for such input mechanisms to be intuitive (since their appearance typically does not change as readily as a displayed object) and to allow for multifunctional use. Combinations of hardware buttons and rotatable and depressible input mechanisms that are multifunctional alone and in combination are highly desirable for providing different user interfaces on a portable multifunction device. 
     Below,  FIGS.  1 A- 1 B,  2 ,  3 ,  4 A- 4 B, and  5 A- 5 B  provide a description of exemplary devices for performing the techniques for button functionalities for user interfaces.  FIGS.  6 - 12    illustrate exemplary button functionalities for user interfaces. The user interfaces in the figures are also used to illustrate the processes described below, including the processes in  FIGS.  13 - 20   . 
     Although the following description uses terms “first,” “second,” etc. to describe various elements, these elements should not be limited by the terms. These terms are only used to distinguish one element from another. For example, a first touch could be termed a second touch, and, similarly, a second touch could be termed a first touch, without departing from the scope of the various described embodiments. The first touch and the second touch are both touches, but they are not the same touch. 
     The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a”, “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The term “if” may be construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” may be construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context. 
     Embodiments of electronic devices, user interfaces for such devices, and associated processes for using such devices are described. In some embodiments, the device is a portable communications device, such as a mobile telephone, that also contains other functions, such as PDA and/or music player functions. Exemplary embodiments of portable multifunction devices include, without limitation, the iPhone®, iPod Touch®, and iPad® devices from Apple Inc. of Cupertino, Calif. Other portable electronic devices, such as laptops or tablet computers with touch-sensitive surfaces (e.g., touch screen displays and/or touchpads), are, optionally, used. It should also be understood that, in some embodiments, the device is not a portable communications device, but is a desktop computer with a touch-sensitive surface (e.g., a touch screen display and/or a touchpad). 
     In the discussion that follows, an electronic device that includes a display and a touch-sensitive surface is described. It should be understood, however, that the electronic device optionally includes one or more other physical user-interface devices, such as a physical keyboard, a mouse, and/or a joystick. 
     The device may support a variety of applications, such as one or more of the following: a drawing application, a presentation application, a word processing application, a website creation application, a disk authoring application, a spreadsheet application, a gaming application, a telephone application, a video conferencing application, an e-mail application, an instant messaging application, a workout support application, a photo management application, a digital camera application, a digital video camera application, a web browsing application, a digital music player application, and/or a digital video player application. 
     The various applications that are executed on the device optionally use at least one common physical user-interface device, such as the touch-sensitive surface. One or more functions of the touch-sensitive surface as well as corresponding information displayed on the device are, optionally, adjusted and/or varied from one application to the next and/or within a respective application. In this way, a common physical architecture (such as the touch-sensitive surface) of the device optionally supports the variety of applications with user interfaces that are intuitive and transparent to the user. 
     Attention is now directed toward embodiments of portable devices with touch-sensitive displays.  FIG.  1 A  is a block diagram illustrating portable multifunction device  100  with touch-sensitive display system  112  in accordance with some embodiments. Touch-sensitive display  112  is sometimes called a “touch screen” for convenience and is sometimes known as or called a “touch-sensitive display system.” Device  100  includes memory  102  (which optionally includes one or more computer-readable storage mediums), memory controller  122 , one or more processing units (CPUs)  120 , peripherals interface  118 , RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , input/output (I/O) subsystem  106 , other input control devices  116 , and external port  124 . Device  100  optionally includes one or more optical sensors  164 . Device  100  optionally includes one or more contact intensity sensors  165  for detecting intensity of contacts on device  100  (e.g., a touch-sensitive surface such as touch-sensitive display system  112  of device  100 ). Device  100  optionally includes one or more tactile output generators  167  for generating tactile outputs on device  100  (e.g., generating tactile outputs on a touch-sensitive surface such as touch-sensitive display system  112  of device  100  or touchpad  355  of device  300 ). These components optionally communicate over one or more communication buses or signal lines  103 . 
     As used in the specification and claims, the term “intensity” of a contact on a touch-sensitive surface refers to the force or pressure (force per unit area) of a contact (e.g., a finger contact) on the touch-sensitive surface, or to a substitute (proxy) for the force or pressure of a contact on the touch-sensitive surface. The intensity of a contact has a range of values that includes at least four distinct values and more typically includes hundreds of distinct values (e.g., at least 256). Intensity of a contact is, optionally, determined (or measured) using various approaches and various sensors or combinations of sensors. For example, one or more force sensors underneath or adjacent to the touch-sensitive surface are, optionally, used to measure force at various points on the touch-sensitive surface. In some implementations, force measurements from multiple force sensors are combined (e.g., a weighted average) to determine an estimated force of a contact. Similarly, a pressure-sensitive tip of a stylus is, optionally, used to determine a pressure of the stylus on the touch-sensitive surface. Alternatively, the size of the contact area detected on the touch-sensitive surface and/or changes thereto, the capacitance of the touch-sensitive surface proximate to the contact and/or changes thereto, and/or the resistance of the touch-sensitive surface proximate to the contact and/or changes thereto are, optionally, used as a substitute for the force or pressure of the contact on the touch-sensitive surface. In some implementations, the substitute measurements for contact force or pressure are used directly to determine whether an intensity threshold has been exceeded (e.g., the intensity threshold is described in units corresponding to the substitute measurements). In some implementations, the substitute measurements for contact force or pressure are converted to an estimated force or pressure, and the estimated force or pressure is used to determine whether an intensity threshold has been exceeded (e.g., the intensity threshold is a pressure threshold measured in units of pressure). Using the intensity of a contact as an attribute of a user input allows for user access to additional device functionality that may otherwise not be accessible by the user on a reduced-size device with limited real estate for displaying affordances (e.g., on a touch-sensitive display) and/or receiving user input (e.g., via a touch-sensitive display, a touch-sensitive surface, or a physical/mechanical control such as a knob or a button). 
     As used in the specification and claims, the term “tactile output” refers to physical displacement of a device relative to a previous position of the device, physical displacement of a component (e.g., a touch-sensitive surface) of a device relative to another component (e.g., housing) of the device, or displacement of the component relative to a center of mass of the device that will be detected by a user with the user&#39;s sense of touch. For example, in situations where the device or the component of the device is in contact with a surface of a user that is sensitive to touch (e.g., a finger, palm, or other part of a user&#39;s hand), the tactile output generated by the physical displacement will be interpreted by the user as a tactile sensation corresponding to a perceived change in physical characteristics of the device or the component of the device. For example, movement of a touch-sensitive surface (e.g., a touch-sensitive display or trackpad) is, optionally, interpreted by the user as a “down click” or “up click” of a physical actuator button. In some cases, a user will feel a tactile sensation such as an “down click” or “up click” even when there is no movement of a physical actuator button associated with the touch-sensitive surface that is physically pressed (e.g., displaced) by the user&#39;s movements. As another example, movement of the touch-sensitive surface is, optionally, interpreted or sensed by the user as “roughness” of the touch-sensitive surface, even when there is no change in smoothness of the touch-sensitive surface. While such interpretations of touch by a user will be subject to the individualized sensory perceptions of the user, there are many sensory perceptions of touch that are common to a large majority of users. Thus, when a tactile output is described as corresponding to a particular sensory perception of a user (e.g., an “up click,” a “down click,” “roughness”), unless otherwise stated, the generated tactile output corresponds to physical displacement of the device or a component thereof that will generate the described sensory perception for a typical (or average) user. 
     It should be appreciated that device  100  is only one example of a portable multifunction device, and that device  100  optionally has more or fewer components than shown, optionally combines two or more components, or optionally has a different configuration or arrangement of the components. The various components shown in  FIG.  1 A  are implemented in hardware, software, or a combination of both hardware and software, including one or more signal processing and/or application-specific integrated circuits. 
     Memory  102  may include one or more computer-readable storage mediums. The computer-readable storage mediums may be tangible and non-transitory. Memory  102  may include high-speed random access memory and may also include non-volatile memory, such as one or more magnetic disk storage devices, flash memory devices, or other non-volatile solid-state memory devices. Memory controller  122  may control access to memory  102  by other components of device  100 . 
     Peripherals interface  118  can be used to couple input and output peripherals of the device to CPU  120  and memory  102 . The one or more processors  120  run or execute various software programs and/or sets of instructions stored in memory  102  to perform various functions for device  100  and to process data. In some embodiments, peripherals interface  118 , CPU  120 , and memory controller  122  may be implemented on a single chip, such as chip  104 . In some other embodiments, they may be implemented on separate chips. 
     RF (radio frequency) circuitry  108  receives and sends RF signals, also called electromagnetic signals. RF circuitry  108  converts electrical signals to/from electromagnetic signals and communicates with communications networks and other communications devices via the electromagnetic signals. RF circuitry  108  optionally includes well-known circuitry for performing these functions, including but not limited to an antenna system, an RF transceiver, one or more amplifiers, a tuner, one or more oscillators, a digital signal processor, a CODEC chipset, a subscriber identity module (SIM) card, memory, and so forth. RF circuitry  108  optionally communicates with networks, such as the Internet, also referred to as the World Wide Web (WWW), an intranet and/or a wireless network, such as a cellular telephone network, a wireless local area network (LAN) and/or a metropolitan area network (MAN), and other devices by wireless communication. The RF circuitry  108  optionally includes well-known circuitry for detecting near field communication (NFC) fields, such as by a short-range communication radio. The wireless communication optionally uses any of a plurality of communications standards, protocols, and technologies, including but not limited to Global System for Mobile Communications (GSM), Enhanced Data GSM Environment (EDGE), high-speed downlink packet access (HSDPA), high-speed uplink packet access (HSDPA), Evolution, Data-Only (EV-DO), HSPA, HSPA+, Dual-Cell HSPA (DC-HSPDA), long term evolution (LTE), near field communication (NFC), wideband code division multiple access (W-CDMA), code division multiple access (CDMA), time division multiple access (TDMA), Bluetooth, Bluetooth Low Energy (BTLE), Wireless Fidelity (Wi-Fi) (e.g., IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, and/or IEEE 802.11ac), voice over Internet Protocol (VoIP), Wi-MAX, a protocol for e-mail (e.g., Internet message access protocol (IMAP) and/or post office protocol (POP)), instant messaging (e.g., extensible messaging and presence protocol (XMPP), Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions (SIMPLE), Instant Messaging and Presence Service (IMPS)), and/or Short Message Service (SMS), or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document. 
     Audio circuitry  110 , speaker  111 , and microphone  113  provide an audio interface between a user and device  100 . Audio circuitry  110  receives audio data from peripherals interface  118 , converts the audio data to an electrical signal, and transmits the electrical signal to speaker  111 . Speaker  111  converts the electrical signal to human-audible sound waves. Audio circuitry  110  also receives electrical signals converted by microphone  113  from sound waves. Audio circuitry  110  converts the electrical signal to audio data and transmits the audio data to peripherals interface  118  for processing. Audio data may be retrieved from and/or transmitted to memory  102  and/or RF circuitry  108  by peripherals interface  118 . In some embodiments, audio circuitry  110  also includes a headset jack (e.g.,  212 ,  FIG.  2   ). The headset jack provides an interface between audio circuitry  110  and removable audio input/output peripherals, such as output-only headphones or a headset with both output (e.g., a headphone for one or both ears) and input (e.g., a microphone). 
     I/O subsystem  106  couples input/output peripherals on device  100 , such as touch screen  112  and other input control devices  116 , to peripherals interface  118 . I/O subsystem  106  optionally includes display controller  156 , optical sensor controller  158 , intensity sensor controller  159 , haptic feedback controller  161 , and one or more input controllers  160  for other input or control devices. The one or more input controllers  160  receive/send electrical signals from/to other input control devices  116 . The other input control devices  116  optionally include physical buttons (e.g., push buttons, rocker buttons, etc.), dials, slider switches, joysticks, click wheels, and so forth. In some alternate embodiments, input controller(s)  160  are, optionally, coupled to any (or none) of the following: a keyboard, an infrared port, a USB port, and a pointer device such as a mouse. The one or more buttons (e.g.,  208 ,  FIG.  2   ) optionally include an up/down button for volume control of speaker  111  and/or microphone  113 . The one or more buttons optionally include a push button (e.g.,  206 ,  FIG.  2   ). 
     A quick press of the push button may disengage a lock of touch screen  112  or begin a process that uses gestures on the touch screen to unlock the device, as described in U.S. patent application Ser. No. 11/322,549, “Unlocking a Device by Performing Gestures on an Unlock Image,” filed Dec. 23, 2005, U.S. Pat. No. 7,657,849, which is hereby incorporated by reference in its entirety. A longer press of the push button (e.g.,  206 ) may turn power to device  100  on or off. The user may be able to customize a functionality of one or more of the buttons. Touch screen  112  is used to implement virtual or soft buttons and one or more soft keyboards. 
     Touch-sensitive display  112  provides an input interface and an output interface between the device and a user. Display controller  156  receives and/or sends electrical signals from/to touch screen  112 . Touch screen  112  displays visual output to the user. The visual output may include graphics, text, icons, video, and any combination thereof (collectively termed “graphics”). In some embodiments, some or all of the visual output may correspond to user-interface objects. 
     Touch screen  112  has a touch-sensitive surface, sensor, or set of sensors that accepts input from the user based on haptic and/or tactile contact. Touch screen  112  and display controller  156  (along with any associated modules and/or sets of instructions in memory  102 ) detect contact (and any movement or breaking of the contact) on touch screen  112  and convert the detected contact into interaction with user-interface objects (e.g., one or more soft keys, icons, web pages, or images) that are displayed on touch screen  112 . In an exemplary embodiment, a point of contact between touch screen  112  and the user corresponds to a finger of the user. 
     Touch screen  112  may use LCD (liquid crystal display) technology, LPD (light emitting polymer display) technology, or LED (light emitting diode) technology, although other display technologies may be used in other embodiments. Touch screen  112  and display controller  156  may detect contact and any movement or breaking thereof using any of a plurality of touch sensing technologies now known or later developed, including but not limited to capacitive, resistive, infrared, and surface acoustic wave technologies, as well as other proximity sensor arrays or other elements for determining one or more points of contact with touch screen  112 . In an exemplary embodiment, projected mutual capacitance sensing technology is used, such as that found in the iPhone® and iPod Touch® from Apple Inc. of Cupertino, Calif. 
     A touch-sensitive display in some embodiments of touch screen  112  may be analogous to the multi-touch sensitive touchpads described in the following U.S. Pat. No. 6,323,846 (Westerman et al.), U.S. Pat. No. 6,570,557 (Westerman et al.), and/or U.S. Pat. No. 6,677,932 (Westerman), and/or U.S. Patent Publication 2002/0015024A1, each of which is hereby incorporated by reference in its entirety. However, touch screen  112  displays visual output from device  100 , whereas touch-sensitive touchpads do not provide visual output. 
     A touch-sensitive display in some embodiments of touch screen  112  may be as described in the following applications: (1) U.S. patent application Ser. No. 11/381,313, “Multipoint Touch Surface Controller,” filed May 2, 2006; (2) U.S. patent application Ser. No. 10/840,862, “Multipoint Touchscreen,” filed May 6, 2004; (3) U.S. patent application Ser. No. 10/903,964, “Gestures For Touch Sensitive Input Devices,” filed Jul. 30, 2004; (4) U.S. patent application Ser. No. 11/048,264, “Gestures For Touch Sensitive Input Devices,” filed Jan. 31, 2005; (5) U.S. patent application Ser. No. 11/038,590, “Mode-Based Graphical User Interfaces For Touch Sensitive Input Devices,” filed Jan. 18, 2005; (6) U.S. patent application Ser. No. 11/228,758, “Virtual Input Device Placement On A Touch Screen User Interface,” filed Sep. 16, 2005; (7) U.S. patent application Ser. No. 11/228,700, “Operation Of A Computer With A Touch Screen Interface,” filed Sep. 16, 2005; (8) U.S. patent application Ser. No. 11/228,737, “Activating Virtual Keys Of A Touch-Screen Virtual Keyboard,” filed Sep. 16, 2005; and (9) U.S. patent application Ser. No. 11/367,749, “Multi-Functional Hand-Held Device,” filed Mar. 3, 2006. All of these applications are incorporated by reference herein in their entirety. 
     Touch screen  112  may have a video resolution in excess of 100 dpi. In some embodiments, the touch screen has a video resolution of approximately 160 dpi. The user may make contact with touch screen  112  using any suitable object or appendage, such as a stylus, a finger, and so forth. In some embodiments, the user interface is designed to work primarily with finger-based contacts and gestures, which can be less precise than stylus-based input due to the larger area of contact of a finger on the touch screen. In some embodiments, the device translates the rough finger-based input into a precise pointer/cursor position or command for performing the actions desired by the user. 
     In some embodiments, in addition to the touch screen, device  100  may include a touchpad (not shown) for activating or deactivating particular functions. In some embodiments, the touchpad is a touch-sensitive area of the device that, unlike the touch screen, does not display visual output. The touchpad may be a touch-sensitive surface that is separate from touch screen  112  or an extension of the touch-sensitive surface formed by the touch screen. 
     Device  100  also includes power system  162  for powering the various components. Power system  162  may include a power management system, one or more power sources (e.g., battery, alternating current (AC)), a recharging system, a power failure detection circuit, a power converter or inverter, a power status indicator (e.g., a light-emitting diode (LED)) and any other components associated with the generation, management and distribution of power in portable devices. 
     Device  100  may also include one or more optical sensors  164 .  FIG.  1 A  shows an optical sensor coupled to optical sensor controller  158  in I/O subsystem  106 . Optical sensor  164  may include charge-coupled device (CCD) or complementary metal-oxide semiconductor (CMOS) phototransistors. Optical sensor  164  receives light from the environment, projected through one or more lenses, and converts the light to data representing an image. In conjunction with imaging module  143  (also called a camera module), optical sensor  164  may capture still images or video. In some embodiments, an optical sensor is located on the back of device  100 , opposite touch screen display  112  on the front of the device so that the touch screen display may be used as a viewfinder for still and/or video image acquisition. In some embodiments, an optical sensor is located on the front of the device so that the user&#39;s image may be obtained for video conferencing while the user views the other video conference participants on the touch screen display. In some embodiments, the position of optical sensor  164  can be changed by the user (e.g., by rotating the lens and the sensor in the device housing) so that a single optical sensor  164  may be used along with the touch screen display for both video conferencing and still and/or video image acquisition. 
     Device  100  optionally also includes one or more contact intensity sensors  165 .  FIG.  1 A  shows a contact intensity sensor coupled to intensity sensor controller  159  in I/O subsystem  106 . Contact intensity sensor  165  optionally includes one or more piezoresistive strain gauges, capacitive force sensors, electric force sensors, piezoelectric force sensors, optical force sensors, capacitive touch-sensitive surfaces, or other intensity sensors (e.g., sensors used to measure the force (or pressure) of a contact on a touch-sensitive surface). Contact intensity sensor  165  receives contact intensity information (e.g., pressure information or a proxy for pressure information) from the environment. In some embodiments, at least one contact intensity sensor is collocated with, or proximate to, a touch-sensitive surface (e.g., touch-sensitive display system  112 ). In some embodiments, at least one contact intensity sensor is located on the back of device  100 , opposite touch screen display  112 , which is located on the front of device  100 . 
     Device  100  may also include one or more proximity sensors  166 .  FIG.  1 A  shows proximity sensor  166  coupled to peripherals interface  118 . Alternately, proximity sensor  166  may be coupled to input controller  160  in I/O subsystem  106 . Proximity sensor  166  may perform as described in U.S. patent application Ser. No. 11/241,839, “Proximity Detector In Handheld Device”; Ser. No. 11/240,788, “Proximity Detector In Handheld Device”; Ser. No. 11/620,702, “Using Ambient Light Sensor To Augment Proximity Sensor Output”; Ser. No. 11/586,862, “Automated Response To And Sensing Of User Activity In Portable Devices”; and Ser. No. 11/638,251, “Methods And Systems For Automatic Configuration Of Peripherals,” which are hereby incorporated by reference in their entirety. In some embodiments, the proximity sensor turns off and disables touch screen  112  when the multifunction device is placed near the user&#39;s ear (e.g., when the user is making a phone call). 
     Device  100  optionally also includes one or more tactile output generators  167 .  FIG.  1 A  shows a tactile output generator coupled to haptic feedback controller  161  in I/O subsystem  106 . Tactile output generator  167  optionally includes one or more electroacoustic devices such as speakers or other audio components and/or electromechanical devices that convert energy into linear motion such as a motor, solenoid, electroactive polymer, piezoelectric actuator, electrostatic actuator, or other tactile output generating component (e.g., a component that converts electrical signals into tactile outputs on the device). Contact intensity sensor  165  receives tactile feedback generation instructions from haptic feedback module  133  and generates tactile outputs on device  100  that are capable of being sensed by a user of device  100 . In some embodiments, at least one tactile output generator is collocated with, or proximate to, a touch-sensitive surface (e.g., touch-sensitive display system  112 ) and, optionally, generates a tactile output by moving the touch-sensitive surface vertically (e.g., in/out of a surface of device  100 ) or laterally (e.g., back and forth in the same plane as a surface of device  100 ). In some embodiments, at least one tactile output generator sensor is located on the back of device  100 , opposite touch screen display  112 , which is located on the front of device  100 . 
     Device  100  may also include one or more accelerometers  168 .  FIG.  1 A  shows accelerometer  168  coupled to peripherals interface  118 . Alternately, accelerometer  168  may be coupled to an input controller  160  in I/O subsystem  106 . Accelerometer  168  may perform as described in U.S. Patent Publication No. 20050190059, “Acceleration-based Theft Detection System for Portable Electronic Devices,” and U.S. Patent Publication No. 20060017692, “Methods And Apparatuses For Operating A Portable Device Based On An Accelerometer,” both of which are incorporated by reference herein in their entirety. In some embodiments, information is displayed on the touch screen display in a portrait view or a landscape view based on an analysis of data received from the one or more accelerometers. Device  100  optionally includes, in addition to accelerometer(s)  168 , a magnetometer (not shown) and a GPS (or GLONASS or other global navigation system) receiver (not shown) for obtaining information concerning the location and orientation (e.g., portrait or landscape) of device  100 . 
     In some embodiments, the software components stored in memory  102  include operating system  126 , communication module (or set of instructions)  128 , contact/motion module (or set of instructions)  130 , graphics module (or set of instructions)  132 , text input module (or set of instructions)  134 , Global Positioning System (GPS) module (or set of instructions)  135 , and applications (or sets of instructions)  136 . Furthermore, in some embodiments, memory  102  ( FIG.  1 A ) or  370  ( FIG.  3   ) stores device/global internal state  157 , as shown in  FIGS.  1 A and  3   . Device/global internal state  157  includes one or more of: active application state, indicating which applications, if any, are currently active; display state, indicating what applications, views or other information occupy various regions of touch screen display  112 ; sensor state, including information obtained from the device&#39;s various sensors and input control devices  116 ; and location information concerning the device&#39;s location and/or attitude. 
     Operating system  126  (e.g., Darwin, RTXC, LINUX, UNIX, OS X, iOS, WINDOWS, or an embedded operating system such as VxWorks) includes various software components and/or drivers for controlling and managing general system tasks (e.g., memory management, storage device control, power management, etc.) and facilitates communication between various hardware and software components. 
     Communication module  128  facilitates communication with other devices over one or more external ports  124  and also includes various software components for handling data received by RF circuitry  108  and/or external port  124 . External port  124  (e.g., Universal Serial Bus (USB), FIREWIRE, etc.) is adapted for coupling directly to other devices or indirectly over a network (e.g., the Internet, wireless LAN, etc.). In some embodiments, the external port is a multi-pin (e.g., 30-pin) connector that is the same as, or similar to and/or compatible with, the 30-pin connector used on iPod® (trademark of Apple Inc.) devices. 
     Contact/motion module  130  optionally detects contact with touch screen  112  (in conjunction with display controller  156 ) and other touch-sensitive devices (e.g., a touchpad or physical click wheel). Contact/motion module  130  includes various software components for performing various operations related to detection of contact, such as determining if contact has occurred (e.g., detecting a finger-down event), determining an intensity of the contact (e.g., the force or pressure of the contact or a substitute for the force or pressure of the contact), determining if there is movement of the contact and tracking the movement across the touch-sensitive surface (e.g., detecting one or more finger-dragging events), and determining if the contact has ceased (e.g., detecting a finger-up event or a break in contact). Contact/motion module  130  receives contact data from the touch-sensitive surface. Determining movement of the point of contact, which is represented by a series of contact data, optionally includes determining speed (magnitude), velocity (magnitude and direction), and/or an acceleration (a change in magnitude and/or direction) of the point of contact. These operations are, optionally, applied to single contacts (e.g., one finger contacts) or to multiple simultaneous contacts (e.g., “multitouch”/multiple finger contacts). In some embodiments, contact/motion module  130  and display controller  156  detect contact on a touchpad. 
     In some embodiments, contact/motion module  130  uses a set of one or more intensity thresholds to determine whether an operation has been performed by a user (e.g., to determine whether a user has “clicked” on an icon). In some embodiments, at least a subset of the intensity thresholds are determined in accordance with software parameters (e.g., the intensity thresholds are not determined by the activation thresholds of particular physical actuators and can be adjusted without changing the physical hardware of device  100 ). For example, a mouse “click” threshold of a trackpad or touch screen display can be set to any of a large range of predefined threshold values without changing the trackpad or touch screen display hardware. Additionally, in some implementations, a user of the device is provided with software settings for adjusting one or more of the set of intensity thresholds (e.g., by adjusting individual intensity thresholds and/or by adjusting a plurality of intensity thresholds at once with a system-level click “intensity” parameter). 
     Contact/motion module  130  optionally detects a gesture input by a user. Different gestures on the touch-sensitive surface have different contact patterns (e.g., different motions, timings, and/or intensities of detected contacts). Thus, a gesture is, optionally, detected by detecting a particular contact pattern. For example, detecting a finger tap gesture includes detecting a finger-down event followed by detecting a finger-up (liftoff) event at the same position (or substantially the same position) as the finger-down event (e.g., at the position of an icon). As another example, detecting a finger swipe gesture on the touch-sensitive surface includes detecting a finger-down event followed by detecting one or more finger-dragging events, and subsequently followed by detecting a finger-up (liftoff) event. 
     Graphics module  132  includes various known software components for rendering and displaying graphics on touch screen  112  or other display, including components for changing the visual impact (e.g., brightness, transparency, saturation, contrast, or other visual property) of graphics that are displayed. As used herein, the term “graphics” includes any object that can be displayed to a user, including, without limitation, text, web pages, icons (such as user-interface objects including soft keys), digital images, videos, animations, and the like. 
     In some embodiments, graphics module  132  stores data representing graphics to be used. Each graphic is, optionally, assigned a corresponding code. Graphics module  132  receives, from applications etc., one or more codes specifying graphics to be displayed along with, if necessary, coordinate data and other graphic property data, and then generates screen image data to output to display controller  156 . 
     Haptic feedback module  133  includes various software components for generating instructions used by tactile output generator(s)  167  to produce tactile outputs at one or more locations on device  100  in response to user interactions with device  100 . 
     Text input module  134 , which may be a component of graphics module  132 , provides soft keyboards for entering text in various applications (e.g., contacts  137 , e-mail  140 , IM  141 , browser  147 , and any other application that needs text input). 
     GPS module  135  determines the location of the device and provides this information for use in various applications (e.g., to telephone  138  for use in location-based dialing; to camera  143  as picture/video metadata; and to applications that provide location-based services such as weather widgets, local yellow page widgets, and map/navigation widgets). 
     Applications  136  may include the following modules (or sets of instructions), or a subset or superset thereof:
         Contacts module  137  (sometimes called an address book or contact list);   Telephone module  138 ;   Video conference module  139 ;   E-mail client module  140 ;   Instant messaging (IM) module  141 ;   Workout support module  142 ;   Camera module  143  for still and/or video images;   Image management module  144 ;   Video player module;   Music player module;   Browser module  147 ;   Calendar module  148 ;   Widget modules  149 , which may include one or more of: weather widget  149 - 1 , stocks widget  149 - 2 , calculator widget  149 - 3 , alarm clock widget  149 - 4 , dictionary widget  149 - 5 , and other widgets obtained by the user, as well as user-created widgets  149 - 6 ;   Widget creator module  150  for making user-created widgets  149 - 6 ;   Search module  151 ;   Video and music player module  152 , which merges video player module and music player module;   Notes module  153 ;   Map module  154 ; and/or   Online video module  155 .       

     Examples of other applications  136  that may be stored in memory  102  include other word processing applications, other image editing applications, drawing applications, presentation applications, JAVA-enabled applications, encryption, digital rights management, voice recognition, and voice replication. 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , contacts module  137  may be used to manage an address book or contact list (e.g., stored in application internal state  192  of contacts module  137  in memory  102  or memory  370 ), including: adding name(s) to the address book; deleting name(s) from the address book; associating telephone number(s), e-mail address(es), physical address(es) or other information with a name; associating an image with a name; categorizing and sorting names; providing telephone numbers or e-mail addresses to initiate and/or facilitate communications by telephone  138 , video conference module  139 , e-mail  140 , or IM  141 ; and so forth. 
     In conjunction with RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , telephone module  138  may be used to enter a sequence of characters corresponding to a telephone number, access one or more telephone numbers in contacts module  137 , modify a telephone number that has been entered, dial a respective telephone number, conduct a conversation, and disconnect or hang up when the conversation is completed. As noted above, the wireless communication may use any of a plurality of communications standards, protocols, and technologies. 
     In conjunction with RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , touch screen  112 , display controller  156 , optical sensor  164 , optical sensor controller  158 , contact/motion module  130 , graphics module  132 , text input module  134 , contacts module  137 , and telephone module  138 , video conference module  139  includes executable instructions to initiate, conduct, and terminate a video conference between a user and one or more other participants in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , e-mail client module  140  includes executable instructions to create, send, receive, and manage e-mail in response to user instructions. In conjunction with image management module  144 , e-mail client module  140  makes it very easy to create and send e-mails with still or video images taken with camera module  143 . 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , the instant messaging module  141  includes executable instructions to enter a sequence of characters corresponding to an instant message, to modify previously entered characters, to transmit a respective instant message (for example, using a Short Message Service (SMS) or Multimedia Message Service (MMS) protocol for telephony-based instant messages or using XMPP, SIMPLE, or IMPS for Internet-based instant messages), to receive instant messages, and to view received instant messages. In some embodiments, transmitted and/or received instant messages may include graphics, photos, audio files, video files and/or other attachments as are supported in an MIMS and/or an Enhanced Messaging Service (EMS). As used herein, “instant messaging” refers to both telephony-based messages (e.g., messages sent using SMS or MMS) and Internet-based messages (e.g., messages sent using XMPP, SIMPLE, or IMPS). 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , GPS module  135 , map module  154 , and music player module, workout support module  142  includes executable instructions to create workouts (e.g., with time, distance, and/or calorie burning goals); communicate with workout sensors (sports devices); receive workout sensor data; calibrate sensors used to monitor a workout; select and play music for a workout; and display, store, and transmit workout data. 
     In conjunction with touch screen  112 , display controller  156 , optical sensor(s)  164 , optical sensor controller  158 , contact/motion module  130 , graphics module  132 , and image management module  144 , camera module  143  includes executable instructions to capture still images or video (including a video stream) and store them into memory  102 , modify characteristics of a still image or video, or delete a still image or video from memory  102 . 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , and camera module  143 , image management module  144  includes executable instructions to arrange, modify (e.g., edit), or otherwise manipulate, label, delete, present (e.g., in a digital slide show or album), and store still and/or video images. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , browser module  147  includes executable instructions to browse the Internet in accordance with user instructions, including searching, linking to, receiving, and displaying web pages or portions thereof, as well as attachments and other files linked to web pages. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , e-mail client module  140 , and browser module  147 , calendar module  148  includes executable instructions to create, display, modify, and store calendars and data associated with calendars (e.g., calendar entries, to-do lists, etc.) in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , and browser module  147 , widget modules  149  are mini-applications that may be downloaded and used by a user (e.g., weather widget  149 - 1 , stocks widget  149 - 2 , calculator widget  149 - 3 , alarm clock widget  149 - 4 , and dictionary widget  149 - 5 ) or created by the user (e.g., user-created widget  149 - 6 ). In some embodiments, a widget includes an HTML (Hypertext Markup Language) file, a CSS (Cascading Style Sheets) file, and a JavaScript file. In some embodiments, a widget includes an XML (Extensible Markup Language) file and a JavaScript file (e.g., Yahoo! Widgets). 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , and browser module  147 , the widget creator module  150  may be used by a user to create widgets (e.g., turning a user-specified portion of a web page into a widget). 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , search module  151  includes executable instructions to search for text, music, sound, image, video, and/or other files in memory  102  that match one or more search criteria (e.g., one or more user-specified search terms) in accordance with user instructions. 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , audio circuitry  110 , speaker  111 , RF circuitry  108 , and browser module  147 , video and music player module  152  includes executable instructions that allow the user to download and play back recorded music and other sound files stored in one or more file formats, such as MP3 or AAC files, and executable instructions to display, present, or otherwise play back videos (e.g., on touch screen  112  or on an external, connected display via external port  124 ). In some embodiments, device  100  optionally includes the functionality of an MP3 player, such as an iPod (trademark of Apple Inc.). 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , notes module  153  includes executable instructions to create and manage notes, to-do lists, and the like in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , GPS module  135 , and browser module  147 , map module  154  may be used to receive, display, modify, and store maps and data associated with maps (e.g., driving directions, data on stores and other points of interest at or near a particular location, and other location-based data) in accordance with user instructions. 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , audio circuitry  110 , speaker  111 , RF circuitry  108 , text input module  134 , e-mail client module  140 , and browser module  147 , online video module  155  includes instructions that allow the user to access, browse, receive (e.g., by streaming and/or download), play back (e.g., on the touch screen or on an external, connected display via external port  124 ), send an e-mail with a link to a particular online video, and otherwise manage online videos in one or more file formats, such as H.264. In some embodiments, instant messaging module  141 , rather than e-mail client module  140 , is used to send a link to a particular online video. Additional description of the online video application can be found in U.S. Provisional Patent Application No. 60/936,562, “Portable Multifunction Device, Method, and Graphical User Interface for Playing Online Videos,” filed Jun. 20, 2007, and U.S. patent application Ser. No. 11/968,067, “Portable Multifunction Device, Method, and Graphical User Interface for Playing Online Videos,” filed Dec. 31, 2007, the contents of which are hereby incorporated by reference in their entirety. 
     Each of the above-identified modules and applications corresponds to a set of executable instructions for performing one or more functions described above and the methods described in this application (e.g., the computer-implemented methods and other information processing methods described herein). These modules (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules, and thus various subsets of these modules may be combined or otherwise rearranged in various embodiments. For example, video player module may be combined with music player module into a single module (e.g., video and music player module  152 ,  FIG.  1 A ). In some embodiments, memory  102  may store a subset of the modules and data structures identified above. Furthermore, memory  102  may store additional modules and data structures not described above. 
     In some embodiments, device  100  is a device where operation of a predefined set of functions on the device is performed exclusively through a touch screen and/or a touchpad. By using a touch screen and/or a touchpad as the primary input control device for operation of device  100 , the number of physical input control devices (such as push buttons, dials, and the like) on device  100  may be reduced. 
     The predefined set of functions that are performed exclusively through a touch screen and/or a touchpad optionally include navigation between user interfaces. In some embodiments, the touchpad, when touched by the user, navigates device  100  to a main, home, or root menu from any user interface that is displayed on device  100 . In such embodiments, a “menu button” is implemented using a touchpad. In some other embodiments, the menu button is a physical push button or other physical input control device instead of a touchpad. 
       FIG.  1 B  is a block diagram illustrating exemplary components for event handling in accordance with some embodiments. In some embodiments, memory  102  ( FIG.  1 A ) or  370  ( FIG.  3   ) includes event sorter  170  (e.g., in operating system  126 ) and a respective application  136 - 1  (e.g., any of the aforementioned applications  137 - 151 ,  155 ,  380 - 390 ). 
     Event sorter  170  receives event information and determines the application  136 - 1  and application view  191  of application  136 - 1  to which to deliver the event information. Event sorter  170  includes event monitor  171  and event dispatcher module  174 . In some embodiments, application  136 - 1  includes application internal state  192 , which indicates the current application view(s) displayed on touch-sensitive display  112  when the application is active or executing. In some embodiments, device/global internal state  157  is used by event sorter  170  to determine which application(s) is (are) currently active, and application internal state  192  is used by event sorter  170  to determine application views  191  to which to deliver event information. 
     In some embodiments, application internal state  192  includes additional information, such as one or more of: resume information to be used when application  136 - 1  resumes execution, user interface state information that indicates information being displayed or that is ready for display by application  136 - 1 , a state queue for enabling the user to go back to a prior state or view of application  136 - 1 , and a redo/undo queue of previous actions taken by the user. 
     Event monitor  171  receives event information from peripherals interface  118 . Event information includes information about a sub-event (e.g., a user touch on touch-sensitive display  112 , as part of a multi-touch gesture). Peripherals interface  118  transmits information it receives from I/O subsystem  106  or a sensor, such as proximity sensor  166 , accelerometer(s)  168 , and/or microphone  113  (through audio circuitry  110 ). Information that peripherals interface  118  receives from I/O subsystem  106  includes information from touch-sensitive display  112  or a touch-sensitive surface. 
     In some embodiments, event monitor  171  sends requests to the peripherals interface  118  at predetermined intervals. In response, peripherals interface  118  transmits event information. In other embodiments, peripherals interface  118  transmits event information only when there is a significant event (e.g., receiving an input above a predetermined noise threshold and/or for more than a predetermined duration). 
     In some embodiments, event sorter  170  also includes a hit view determination module  172  and/or an active event recognizer determination module  173 . 
     Hit view determination module  172  provides software procedures for determining where a sub-event has taken place within one or more views when touch-sensitive display  112  displays more than one view. Views are made up of controls and other elements that a user can see on the display. 
     Another aspect of the user interface associated with an application is a set of views, sometimes herein called application views or user interface windows, in which information is displayed and touch-based gestures occur. The application views (of a respective application) in which a touch is detected may correspond to programmatic levels within a programmatic or view hierarchy of the application. For example, the lowest level view in which a touch is detected may be called the hit view, and the set of events that are recognized as proper inputs may be determined based, at least in part, on the hit view of the initial touch that begins a touch-based gesture. 
     Hit view determination module  172  receives information related to sub-events of a touch-based gesture. When an application has multiple views organized in a hierarchy, hit view determination module  172  identifies a hit view as the lowest view in the hierarchy which should handle the sub-event. In most circumstances, the hit view is the lowest level view in which an initiating sub-event occurs (e.g., the first sub-event in the sequence of sub-events that form an event or potential event). Once the hit view is identified by the hit view determination module  172 , the hit view typically receives all sub-events related to the same touch or input source for which it was identified as the hit view. 
     Active event recognizer determination module  173  determines which view or views within a view hierarchy should receive a particular sequence of sub-events. In some embodiments, active event recognizer determination module  173  determines that only the hit view should receive a particular sequence of sub-events. In other embodiments, active event recognizer determination module  173  determines that all views that include the physical location of a sub-event are actively involved views, and therefore determines that all actively involved views should receive a particular sequence of sub-events. In other embodiments, even if touch sub-events were entirely confined to the area associated with one particular view, views higher in the hierarchy would still remain as actively involved views. 
     Event dispatcher module  174  dispatches the event information to an event recognizer (e.g., event recognizer  180 ). In embodiments including active event recognizer determination module  173 , event dispatcher module  174  delivers the event information to an event recognizer determined by active event recognizer determination module  173 . In some embodiments, event dispatcher module  174  stores in an event queue the event information, which is retrieved by a respective event receiver  182 . 
     In some embodiments, operating system  126  includes event sorter  170 . Alternatively, application  136 - 1  includes event sorter  170 . In yet other embodiments, event sorter  170  is a stand-alone module, or a part of another module stored in memory  102 , such as contact/motion module  130 . 
     In some embodiments, application  136 - 1  includes a plurality of event handlers  190  and one or more application views  191 , each of which includes instructions for handling touch events that occur within a respective view of the application&#39;s user interface. Each application view  191  of the application  136 - 1  includes one or more event recognizers  180 . Typically, a respective application view  191  includes a plurality of event recognizers  180 . In other embodiments, one or more of event recognizers  180  are part of a separate module, such as a user interface kit (not shown) or a higher level object from which application  136 - 1  inherits methods and other properties. In some embodiments, a respective event handler  190  includes one or more of: data updater  176 , object updater  177 , GUI updater  178 , and/or event data  179  received from event sorter  170 . Event handler  190  may utilize or call data updater  176 , object updater  177 , or GUI updater  178  to update the application internal state  192 . Alternatively, one or more of the application views  191  include one or more respective event handlers  190 . Also, in some embodiments, one or more of data updater  176 , object updater  177 , and GUI updater  178  are included in a respective application view  191 . 
     A respective event recognizer  180  receives event information (e.g., event data  179 ) from event sorter  170  and identifies an event from the event information. Event recognizer  180  includes event receiver  182  and event comparator  184 . In some embodiments, event recognizer  180  also includes at least a subset of: metadata  183 , and event delivery instructions  188  (which may include sub-event delivery instructions). 
     Event receiver  182  receives event information from event sorter  170 . The event information includes information about a sub-event, for example, a touch or a touch movement. Depending on the sub-event, the event information also includes additional information, such as location of the sub-event. When the sub-event concerns motion of a touch, the event information may also include speed and direction of the sub-event. In some embodiments, events include rotation of the device from one orientation to another (e.g., from a portrait orientation to a landscape orientation, or vice versa), and the event information includes corresponding information about the current orientation (also called device attitude) of the device. 
     Event comparator  184  compares the event information to predefined event or sub-event definitions and, based on the comparison, determines an event or sub-event, or determines or updates the state of an event or sub-event. In some embodiments, event comparator  184  includes event definitions  186 . Event definitions  186  contain definitions of events (e.g., predefined sequences of sub-events), for example, event 1 ( 187 - 1 ), event 2 ( 187 - 2 ), and others. In some embodiments, sub-events in an event ( 187 ) include, for example, touch begin, touch end, touch movement, touch cancellation, and multiple touching. In one example, the definition for event 1 ( 187 - 1 ) is a double tap on a displayed object. The double tap, for example, comprises a first touch (touch begin) on the displayed object for a predetermined phase, a first liftoff (touch end) for a predetermined phase, a second touch (touch begin) on the displayed object for a predetermined phase, and a second liftoff (touch end) for a predetermined phase. In another example, the definition for event 2 ( 187 - 2 ) is a dragging on a displayed object. The dragging, for example, comprises a touch (or contact) on the displayed object for a predetermined phase, a movement of the touch across touch-sensitive display  112 , and liftoff of the touch (touch end). In some embodiments, the event also includes information for one or more associated event handlers  190 . 
     In some embodiments, event definition  187  includes a definition of an event for a respective user-interface object. In some embodiments, event comparator  184  performs a hit test to determine which user-interface object is associated with a sub-event. For example, in an application view in which three user-interface objects are displayed on touch-sensitive display  112 , when a touch is detected on touch-sensitive display  112 , event comparator  184  performs a hit test to determine which of the three user-interface objects is associated with the touch (sub-event). If each displayed object is associated with a respective event handler  190 , the event comparator uses the result of the hit test to determine which event handler  190  should be activated. For example, event comparator  184  selects an event handler associated with the sub-event and the object triggering the hit test. 
     In some embodiments, the definition for a respective event ( 187 ) also includes delayed actions that delay delivery of the event information until after it has been determined whether the sequence of sub-events does or does not correspond to the event recognizer&#39;s event type. 
     When a respective event recognizer  180  determines that the series of sub-events do not match any of the events in event definitions  186 , the respective event recognizer  180  enters an event impossible, event failed, or event ended state, after which it disregards subsequent sub-events of the touch-based gesture. In this situation, other event recognizers, if any, that remain active for the hit view continue to track and process sub-events of an ongoing touch-based gesture. 
     In some embodiments, a respective event recognizer  180  includes metadata  183  with configurable properties, flags, and/or lists that indicate how the event delivery system should perform sub-event delivery to actively involved event recognizers. In some embodiments, metadata  183  includes configurable properties, flags, and/or lists that indicate how event recognizers may interact, or are enabled to interact, with one another. In some embodiments, metadata  183  includes configurable properties, flags, and/or lists that indicate whether sub-events are delivered to varying levels in the view or programmatic hierarchy. 
     In some embodiments, a respective event recognizer  180  activates event handler  190  associated with an event when one or more particular sub-events of an event are recognized. In some embodiments, a respective event recognizer  180  delivers event information associated with the event to event handler  190 . Activating an event handler  190  is distinct from sending (and deferred sending) sub-events to a respective hit view. In some embodiments, event recognizer  180  throws a flag associated with the recognized event, and event handler  190  associated with the flag catches the flag and performs a predefined process. 
     In some embodiments, event delivery instructions  188  include sub-event delivery instructions that deliver event information about a sub-event without activating an event handler. Instead, the sub-event delivery instructions deliver event information to event handlers associated with the series of sub-events or to actively involved views. Event handlers associated with the series of sub-events or with actively involved views receive the event information and perform a predetermined process. 
     In some embodiments, data updater  176  creates and updates data used in application  136 - 1 . For example, data updater  176  updates the telephone number used in contacts module  137 , or stores a video file used in video player module. In some embodiments, object updater  177  creates and updates objects used in application  136 - 1 . For example, object updater  177  creates a new user-interface object or updates the position of a user-interface object. GUI updater  178  updates the GUI. For example, GUI updater  178  prepares display information and sends it to graphics module  132  for display on a touch-sensitive display. 
     In some embodiments, event handler(s)  190  includes or has access to data updater  176 , object updater  177 , and GUI updater  178 . In some embodiments, data updater  176 , object updater  177 , and GUI updater  178  are included in a single module of a respective application  136 - 1  or application view  191 . In other embodiments, they are included in two or more software modules. 
     It shall be understood that the foregoing discussion regarding event handling of user touches on touch-sensitive displays also applies to other forms of user inputs to operate multifunction devices  100  with input devices, not all of which are initiated on touch screens. For example, mouse movement and mouse button presses, optionally coordinated with single or multiple keyboard presses or holds; contact movements such as taps, drags, scrolls, etc. on touchpads; pen stylus inputs; movement of the device; oral instructions; detected eye movements; biometric inputs; and/or any combination thereof are optionally utilized as inputs corresponding to sub-events which define an event to be recognized. 
       FIG.  2    illustrates a portable multifunction device  100  having a touch screen  112  in accordance with some embodiments. The touch screen optionally displays one or more graphics within user interface (UI)  200 . In this embodiment, as well as others described below, a user is enabled to select one or more of the graphics by making a gesture on the graphics, for example, with one or more fingers  202  (not drawn to scale in the figure) or one or more styluses  203  (not drawn to scale in the figure). In some embodiments, selection of one or more graphics occurs when the user breaks contact with the one or more graphics. In some embodiments, the gesture optionally includes one or more taps, one or more swipes (from left to right, right to left, upward and/or downward), and/or a rolling of a finger (from right to left, left to right, upward and/or downward) that has made contact with device  100 . In some implementations or circumstances, inadvertent contact with a graphic does not select the graphic. For example, a swipe gesture that sweeps over an application icon optionally does not select the corresponding application when the gesture corresponding to selection is a tap. 
     Device  100  may also include one or more physical buttons, such as “home” or menu button  204 . As described previously, menu button  204  may be used to navigate to any application  136  in a set of applications that may be executed on device  100 . Alternatively, in some embodiments, the menu button is implemented as a soft key in a GUI displayed on touch screen  112 . 
     In one embodiment, device  100  includes touch screen  112 , menu button  204 , push button  206  for powering the device on/off and locking the device, volume adjustment button(s)  208 , subscriber identity module (SIM) card slot  210 , headset jack  212 , and docking/charging external port  124 . Push button  206  is, optionally, used to turn the power on/off on the device by depressing the button and holding the button in the depressed state for a predefined time interval; to lock the device by depressing the button and releasing the button before the predefined time interval has elapsed; and/or to unlock the device or initiate an unlock process. In an alternative embodiment, device  100  also accepts verbal input for activation or deactivation of some functions through microphone  113 . Device  100  also, optionally, includes one or more contact intensity sensors  165  for detecting intensity of contacts on touch screen  112  and/or one or more tactile output generators  167  for generating tactile outputs for a user of device  100 . 
       FIG.  3    is a block diagram of an exemplary multifunction device with a display and a touch-sensitive surface in accordance with some embodiments. Device  300  need not be portable. In some embodiments, device  300  is a laptop computer, a desktop computer, a tablet computer, a multimedia player device, a navigation device, an educational device (such as a child&#39;s learning toy), a gaming system, or a control device (e.g., a home or industrial controller). Device  300  typically includes one or more processing units (CPUs)  310 , one or more network or other communications interfaces  360 , memory  370 , and one or more communication buses  320  for interconnecting these components. Communication buses  320  optionally include circuitry (sometimes called a chipset) that interconnects and controls communications between system components. Device  300  includes input/output (I/O) interface  330  comprising display  340 , which is typically a touch screen display. I/O interface  330  also optionally includes a keyboard and/or mouse (or other pointing device)  350  and touchpad  355 , tactile output generator  357  for generating tactile outputs on device  300  (e.g., similar to tactile output generator(s)  167  described above with reference to  FIG.  1 A ), sensors  359  (e.g., optical, acceleration, proximity, touch-sensitive, and/or contact intensity sensors similar to contact intensity sensor(s)  165  described above with reference to  FIG.  1 A ). Memory  370  includes high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid state memory devices; and optionally includes non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory  370  optionally includes one or more storage devices remotely located from CPU(s)  310 . In some embodiments, memory  370  stores programs, modules, and data structures analogous to the programs, modules, and data structures stored in memory  102  of portable multifunction device  100  ( FIG.  1 A ), or a subset thereof. Furthermore, memory  370  optionally stores additional programs, modules, and data structures not present in memory  102  of portable multifunction device  100 . For example, memory  370  of device  300  optionally stores drawing module  380 , presentation module  382 , word processing module  384 , website creation module  386 , disk authoring module  388 , and/or spreadsheet module  390 , while memory  102  of portable multifunction device  100  ( FIG.  1 A ) optionally does not store these modules. 
     Each of the above-identified elements in  FIG.  3    may be stored in one or more of the previously mentioned memory devices. Each of the above-identified modules corresponds to a set of instructions for performing a function described above. The above-identified modules or programs (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules, and thus various subsets of these modules may be combined or otherwise rearranged in various embodiments. In some embodiments, memory  370  may store a subset of the modules and data structures identified above. Furthermore, memory  370  may store additional modules and data structures not described above. 
     Attention is now directed towards embodiments of user interfaces that may be implemented on, for example, portable multifunction device  100 . 
       FIG.  4 A  illustrates an exemplary user interface for a menu of applications on portable multifunction device  100  in accordance with some embodiments. Similar user interfaces may be implemented on device  300 . In some embodiments, user interface  400  includes the following elements, or a subset or superset thereof:
         Signal strength indicator(s)  402  for wireless communication(s), such as cellular and Wi-Fi signals;   Time  404 ;   Bluetooth indicator  405 ;   Battery status indicator  406 ;   Tray  408  with icons for frequently used applications, such as:
           Icon  416  for telephone module  138 , labeled “Phone,” which optionally includes an indicator  414  of the number of missed calls or voicemail messages;   Icon  418  for e-mail client module  140 , labeled “Mail,” which optionally includes an indicator  410  of the number of unread e-mails;   Icon  420  for browser module  147 , labeled “Browser;” and   Icon  422  for video and music player module  152 , also referred to as iPod (trademark of Apple Inc.) module  152 , labeled “iPod;” and   
           Icons for other applications, such as:
           Icon  424  for IM module  141 , labeled “Messages;”   Icon  426  for calendar module  148 , labeled “Calendar;”   Icon  428  for image management module  144 , labeled “Photos;”   Icon  430  for camera module  143 , labeled “Camera;”   Icon  432  for online video module  155 , labeled “Online Video;”   Icon  434  for stocks widget  149 - 2 , labeled “Stocks;”   Icon  436  for map module  154 , labeled “Maps;”   Icon  438  for weather widget  149 - 1 , labeled “Weather;”   Icon  440  for alarm clock widget  149 - 4 , labeled “Clock;”   Icon  442  for workout support module  142 , labeled “Workout Support;”   Icon  444  for notes module  153 , labeled “Notes;” and   Icon  446  for a settings application or module, labeled “Settings,” which provides access to settings for device  100  and its various applications  136 .   
               

     It should be noted that the icon labels illustrated in  FIG.  4 A  are merely exemplary. For example, icon  422  for video and music player module  152  may optionally be labeled “Music” or “Music Player.” Other labels are, optionally, used for various application icons. In some embodiments, a label for a respective application icon includes a name of an application corresponding to the respective application icon. In some embodiments, a label for a particular application icon is distinct from a name of an application corresponding to the particular application icon. 
       FIG.  4 B  illustrates an exemplary user interface on a device (e.g., device  300 ,  FIG.  3   ) with a touch-sensitive surface  451  (e.g., a tablet or touchpad  355 ,  FIG.  3   ) that is separate from the display  450  (e.g., touch screen display  112 ). Device  300  also, optionally, includes one or more contact intensity sensors (e.g., one or more of sensors  357 ) for detecting intensity of contacts on touch-sensitive surface  451  and/or one or more tactile output generators  359  for generating tactile outputs for a user of device  300 . 
     Although some of the examples which follow will be given with reference to inputs on touch screen display  112  (where the touch-sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface that is separate from the display, as shown in  FIG.  4 B . In some embodiments, the touch-sensitive surface (e.g.,  451  in  FIG.  4 B ) has a primary axis (e.g.,  452  in  FIG.  4 B ) that corresponds to a primary axis (e.g.,  453  in  FIG.  4 B ) on the display (e.g.,  450 ). In accordance with these embodiments, the device detects contacts (e.g.,  460  and  462  in  FIG.  4 B ) with the touch-sensitive surface  451  at locations that correspond to respective locations on the display (e.g., in  FIG.  4 B,  460    corresponds to  468  and  462  corresponds to  470 ). In this way, user inputs (e.g., contacts  460  and  462 , and movements thereof) detected by the device on the touch-sensitive surface (e.g.,  451  in  FIG.  4 B ) are used by the device to manipulate the user interface on the display (e.g.,  450  in  FIG.  4 B ) of the multifunction device when the touch-sensitive surface is separate from the display. It should be understood that similar methods are, optionally, used for other user interfaces described herein. 
     Additionally, while the following examples are given primarily with reference to finger inputs (e.g., finger contacts, finger tap gestures, finger swipe gestures), it should be understood that, in some embodiments, one or more of the finger inputs are replaced with input from another input device (e.g., a mouse-based input or stylus input). For example, a swipe gesture is, optionally, replaced with a mouse click (e.g., instead of a contact) followed by movement of the cursor along the path of the swipe (e.g., instead of movement of the contact). As another example, a tap gesture is, optionally, replaced with a mouse click while the cursor is located over the location of the tap gesture (e.g., instead of detection of the contact followed by ceasing to detect the contact). Similarly, when multiple user inputs are simultaneously detected, it should be understood that multiple computer mice are, optionally, used simultaneously, or a mouse and finger contacts are, optionally, used simultaneously. 
       FIG.  5 A  illustrates exemplary personal electronic device  500 . Device  500  includes body  502 . In some embodiments, device  500  can include some or all of the features described with respect to devices  100  and  300  (e.g.,  FIGS.  1 A- 4 B ). In some embodiments, device  500  has touch-sensitive display screen  504 , hereafter touch screen  504 . Alternatively, or in addition to touch screen  504 , device  500  has a display and a touch-sensitive surface. As with devices  100  and  300 , in some embodiments, touch screen  504  (or the touch-sensitive surface) may have one or more intensity sensors for detecting intensity of contacts (e.g., touches) being applied. The one or more intensity sensors of touch screen  504  (or the touch-sensitive surface) can provide output data that represents the intensity of touches. The user interface of device  500  can respond to touches based on their intensity, meaning that touches of different intensities can invoke different user interface operations on device  500 . 
     Techniques for detecting and processing touch intensity may be found, for example, in related applications: International Patent Application Serial No. PCT/US2013/040061, titled “Device, Method, and Graphical User Interface for Displaying User Interface Objects Corresponding to an Application,” filed May 8, 2013, and International Patent Application Serial No. PCT/US2013/069483, titled “Device, Method, and Graphical User Interface for Transitioning Between Touch Input to Display Output Relationships,” filed Nov. 11, 2013, each of which is hereby incorporated by reference in their entirety. 
     In some embodiments, device  500  has one or more input mechanisms  506  and  508 . Input mechanisms  506  and  508 , if included, can be physical. Examples of physical input mechanisms include push buttons and rotatable mechanisms. In some embodiments, device  500  has one or more attachment mechanisms. Such attachment mechanisms, if included, can permit attachment of device  500  with, for example, hats, eyewear, earrings, necklaces, shirts, jackets, bracelets, watch straps, chains, trousers, belts, shoes, purses, backpacks, and so forth. These attachment mechanisms may permit device  500  to be worn by a user. 
       FIG.  5 B  depicts exemplary personal electronic device  500 . In some embodiments, device  500  can include some or all of the components described with respect to  FIGS.  1 A,  1 B , and  3 . Device  500  has bus  512  that operatively couples I/O section  514  with one or more computer processors  516  and memory  518 . I/O section  514  can be connected to display  504 , which can have touch-sensitive component  522  and, optionally, touch-intensity sensitive component  524 . In addition, I/O section  514  can be connected with communication unit  530  for receiving application and operating system data, using Wi-Fi, Bluetooth, near field communication (NFC), cellular, and/or other wireless communication techniques. Device  500  can include input mechanisms  506  and/or  508 . Input mechanism  506  may be a rotatable input device or a depressible and rotatable input device, for example. Input mechanism  508  may be a button, in some examples. 
     Input mechanism  508  may be a microphone, in some examples. Personal electronic device  500  can include various sensors, such as GPS sensor  532 , accelerometer  534 , directional sensor  540  (e.g., compass), gyroscope  536 , motion sensor  538 , and/or a combination thereof, all of which can be operatively connected to I/O section  514 . 
     Memory  518  of personal electronic device  500  can be a non-transitory computer-readable storage medium, for storing computer-executable instructions, which, when executed by one or more computer processors  516 , for example, can cause the computer processors to perform the techniques described above, including processes  1300 - 2000  ( FIGS.  13 - 20   ). The computer-executable instructions can also be stored and/or transported within any non-transitory computer-readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For purposes of this document, a “non-transitory computer-readable storage medium” can be any medium that can tangibly contain or store computer-executable instructions for use by or in connection with the instruction execution system, apparatus, or device. The non-transitory computer-readable storage medium can include, but is not limited to, magnetic, optical, and/or semiconductor storages. Examples of such storage include magnetic disks, optical discs based on CD, DVD, or Blu-ray technologies, as well as persistent solid-state memory such as flash, solid-state drives, and the like. Personal electronic device  500  is not limited to the components and configuration of  FIG.  5 B , but can include other or additional components in multiple configurations. 
     As used here, the term “affordance” refers to a user-interactive graphical user interface object that may be displayed on the display screen of devices  100 ,  300 , and/or  500  ( FIGS.  1 ,  3 , and  5   ). For example, an image (e.g., icon), a button, and text (e.g., hyperlink) may each constitute an affordance. 
     As used herein, the term “focus selector” refers to an input element that indicates a current part of a user interface with which a user is interacting. In some implementations that include a cursor or other location marker, the cursor acts as a “focus selector” so that when an input (e.g., a press input) is detected on a touch-sensitive surface (e.g., touchpad  355  in  FIG.  3    or touch-sensitive surface  451  in  FIG.  4 B ) while the cursor is over a particular user interface element (e.g., a button, window, slider or other user interface element), the particular user interface element is adjusted in accordance with the detected input. In some implementations that include a touch screen display (e.g., touch-sensitive display system  112  in  FIG.  1 A  or touch screen  112  in  FIG.  4 A ) that enables direct interaction with user interface elements on the touch screen display, a detected contact on the touch screen acts as a “focus selector” so that when an input (e.g., a press input by the contact) is detected on the touch screen display at a location of a particular user interface element (e.g., a button, window, slider, or other user interface element), the particular user interface element is adjusted in accordance with the detected input. In some implementations, focus is moved from one region of a user interface to another region of the user interface without corresponding movement of a cursor or movement of a contact on a touch screen display (e.g., by using a tab key or arrow keys to move focus from one button to another button); in these implementations, the focus selector moves in accordance with movement of focus between different regions of the user interface. Without regard to the specific form taken by the focus selector, the focus selector is generally the user interface element (or contact on a touch screen display) that is controlled by the user so as to communicate the user&#39;s intended interaction with the user interface (e.g., by indicating, to the device, the element of the user interface with which the user is intending to interact). For example, the location of a focus selector (e.g., a cursor, a contact, or a selection box) over a respective button while a press input is detected on the touch-sensitive surface (e.g., a touchpad or touch screen) will indicate that the user is intending to activate the respective button (as opposed to other user interface elements shown on a display of the device). 
     As used in the specification and claims, the term “characteristic intensity” of a contact refers to a characteristic of the contact based on one or more intensities of the contact. In some embodiments, the characteristic intensity is based on multiple intensity samples. The characteristic intensity is, optionally, based on a predefined number of intensity samples, or a set of intensity samples collected during a predetermined time period (e.g., 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10 seconds) relative to a predefined event (e.g., after detecting the contact, prior to detecting liftoff of the contact, before or after detecting a start of movement of the contact, prior to detecting an end of the contact, before or after detecting an increase in intensity of the contact, and/or before or after detecting a decrease in intensity of the contact). A characteristic intensity of a contact is, optionally based on one or more of: a maximum value of the intensities of the contact, a mean value of the intensities of the contact, an average value of the intensities of the contact, a top 10 percentile value of the intensities of the contact, a value at the half maximum of the intensities of the contact, a value at the 90 percent maximum of the intensities of the contact, or the like. In some embodiments, the duration of the contact is used in determining the characteristic intensity (e.g., when the characteristic intensity is an average of the intensity of the contact over time). In some embodiments, the characteristic intensity is compared to a set of one or more intensity thresholds to determine whether an operation has been performed by a user. For example, the set of one or more intensity thresholds may include a first intensity threshold and a second intensity threshold. In this example, a contact with a characteristic intensity that does not exceed the first threshold results in a first operation, a contact with a characteristic intensity that exceeds the first intensity threshold and does not exceed the second intensity threshold results in a second operation, and a contact with a characteristic intensity that exceeds the second threshold results in a third operation. In some embodiments, a comparison between the characteristic intensity and one or more thresholds is used to determine whether or not to perform one or more operations (e.g., whether to perform a respective operation or forgo performing the respective operation) rather than being used to determine whether to perform a first operation or a second operation. 
     In some embodiments, a portion of a gesture is identified for purposes of determining a characteristic intensity. For example, a touch-sensitive surface may receive a continuous swipe contact transitioning from a start location and reaching an end location, at which point the intensity of the contact increases. In this example, the characteristic intensity of the contact at the end location may be based on only a portion of the continuous swipe contact, and not the entire swipe contact (e.g., only the portion of the swipe contact at the end location). In some embodiments, a smoothing algorithm may be applied to the intensities of the swipe contact prior to determining the characteristic intensity of the contact. For example, the smoothing algorithm optionally includes one or more of: an unweighted sliding-average smoothing algorithm, a triangular smoothing algorithm, a median filter smoothing algorithm, and/or an exponential smoothing algorithm. In some circumstances, these smoothing algorithms eliminate narrow spikes or dips in the intensities of the swipe contact for purposes of determining a characteristic intensity. 
     The intensity of a contact on the touch-sensitive surface may be characterized relative to one or more intensity thresholds, such as a contact-detection intensity threshold, a light press intensity threshold, a deep press intensity threshold, and/or one or more other intensity thresholds. In some embodiments, the light press intensity threshold corresponds to an intensity at which the device will perform operations typically associated with clicking a button of a physical mouse or a trackpad. In some embodiments, the deep press intensity threshold corresponds to an intensity at which the device will perform operations that are different from operations typically associated with clicking a button of a physical mouse or a trackpad. In some embodiments, when a contact is detected with a characteristic intensity below the light press intensity threshold (e.g., and above a nominal contact-detection intensity threshold below which the contact is no longer detected), the device will move a focus selector in accordance with movement of the contact on the touch-sensitive surface without performing an operation associated with the light press intensity threshold or the deep press intensity threshold. Generally, unless otherwise stated, these intensity thresholds are consistent between different sets of user interface figures. 
     An increase of characteristic intensity of the contact from an intensity below the light press intensity threshold to an intensity between the light press intensity threshold and the deep press intensity threshold is sometimes referred to as a “light press” input. An increase of characteristic intensity of the contact from an intensity below the deep press intensity threshold to an intensity above the deep press intensity threshold is sometimes referred to as a “deep press” input. An increase of characteristic intensity of the contact from an intensity below the contact-detection intensity threshold to an intensity between the contact-detection intensity threshold and the light press intensity threshold is sometimes referred to as detecting the contact on the touch-surface. A decrease of characteristic intensity of the contact from an intensity above the contact-detection intensity threshold to an intensity below the contact-detection intensity threshold is sometimes referred to as detecting liftoff of the contact from the touch-surface. In some embodiments, the contact-detection intensity threshold is zero. In some embodiments, the contact-detection intensity threshold is greater than zero. 
     In some embodiments described herein, one or more operations are performed in response to detecting a gesture that includes a respective press input or in response to detecting the respective press input performed with a respective contact (or a plurality of contacts), where the respective press input is detected based at least in part on detecting an increase in intensity of the contact (or plurality of contacts) above a press-input intensity threshold. In some embodiments, the respective operation is performed in response to detecting the increase in intensity of the respective contact above the press-input intensity threshold (e.g., a “down stroke” of the respective press input). In some embodiments, the press input includes an increase in intensity of the respective contact above the press-input intensity threshold and a subsequent decrease in intensity of the contact below the press-input intensity threshold, and the respective operation is performed in response to detecting the subsequent decrease in intensity of the respective contact below the press-input threshold (e.g., an “up stroke” of the respective press input). 
     In some embodiments, the device employs intensity hysteresis to avoid accidental inputs sometimes termed “jitter,” where the device defines or selects a hysteresis intensity threshold with a predefined relationship to the press-input intensity threshold (e.g., the hysteresis intensity threshold is X intensity units lower than the press-input intensity threshold or the hysteresis intensity threshold is 75%, 90%, or some reasonable proportion of the press-input intensity threshold). Thus, in some embodiments, the press input includes an increase in intensity of the respective contact above the press-input intensity threshold and a subsequent decrease in intensity of the contact below the hysteresis intensity threshold that corresponds to the press-input intensity threshold, and the respective operation is performed in response to detecting the subsequent decrease in intensity of the respective contact below the hysteresis intensity threshold (e.g., an “up stroke” of the respective press input). Similarly, in some embodiments, the press input is detected only when the device detects an increase in intensity of the contact from an intensity at or below the hysteresis intensity threshold to an intensity at or above the press-input intensity threshold and, optionally, a subsequent decrease in intensity of the contact to an intensity at or below the hysteresis intensity, and the respective operation is performed in response to detecting the press input (e.g., the increase in intensity of the contact or the decrease in intensity of the contact, depending on the circumstances). 
     For ease of explanation, the descriptions of operations performed in response to a press input associated with a press-input intensity threshold or in response to a gesture including the press input are, optionally, triggered in response to detecting either: an increase in intensity of a contact above the press-input intensity threshold, an increase in intensity of a contact from an intensity below the hysteresis intensity threshold to an intensity above the press-input intensity threshold, a decrease in intensity of the contact below the press-input intensity threshold, and/or a decrease in intensity of the contact below the hysteresis intensity threshold corresponding to the press-input intensity threshold. Additionally, in examples where an operation is described as being performed in response to detecting a decrease in intensity of a contact below the press-input intensity threshold, the operation is, optionally, performed in response to detecting a decrease in intensity of the contact below a hysteresis intensity threshold corresponding to, and lower than, the press-input intensity threshold. 
       FIG.  6 A  shows exemplary button functionalities for user interfaces that may be operated on device  600 . Device  600  may be device  100 ,  300 , or  500  in some embodiments. The electronic device has a display (e.g.,  504 ). As shown in  FIG.  6 A , device  600  includes rotatable and depressible input mechanism  602 . A rotatable and depressible input mechanism adds functionality to device  600  by providing multiple modes of user activation, thereby increasing user interactivity and/or ease of use with any of the user interfaces operable on device  600 . The electronic device may also include a touch-sensitive surface (e.g.,  504 ) and a button (e.g.,  508 ). 
     A user may activate rotatable and depressible input mechanism  602  by activation  604 . Depicted activation arrow blocks (e.g., activation  604 ) are typically not part of the displayed user interface, but are provided to aid in the interpretation of the figures. As depicted in  FIG.  6 A  by the arrow block, activation  604  has an associated activation duration (e.g., a duration of time during which the activation is continuously detected by the device). In response to receiving data representing the activation, the device determines whether the activation duration exceeds a predetermined threshold. In some embodiments, the predetermined threshold is a predetermined length of time. In response to receiving data representing the activation, the device also determines a state of an active application. An active application may include a current application, a home screen of the device, a clock face displayed on the device, and so forth. For example, a state of a current application could be a state of an application with which the user is currently interacting. Alternatively, a state of an active application could refer to a currently displayed screen on the device, such as a clock face or a home screen. 
     In accordance with a determination that the activation duration exceeds the predetermined threshold (e.g., the input is an extended press of rotatable and depressible input mechanism  602 , as depicted by the long arrow block shown for activation  604 ), and in accordance with a determination of the state of the active application, the device performs an action. In some embodiments, the action may be related or otherwise corresponding to the state of the active application. For example, the device may perform an action that is related to the currently displayed content or user interface of the device. In this way, the rotatable and depressible input mechanism may provide different functionalities depending on how the user is interacting with the device (e.g., a displayed user interface). 
     In some embodiments, a rotatable and depressible input mechanism (e.g.,  602 ) is a mechanical button that is rotatable, and the activation is a physical depression of the mechanical button. In some embodiments, a rotatable and depressible input mechanism (e.g.,  602 ) is a capacitive button that is rotatable, and the activation is a touch on the capacitive button. In either case, the rotatable and depressible input mechanism retains two modes of user interaction, which advantageously may be used for different purposes. In some embodiments, the activation (e.g.,  604 ) does not represent a rotation of the rotatable and depressible input mechanism. In some embodiments, detection of the activation is based on detecting a press such as a physical depression or a touch and does not require a rotation for detection. For example, the device may perform an action in response to an activation of rotatable and depressible input mechanism  602 , and it may scroll or cycle through content or options based on the action in response to a rotation. 
     In some embodiments, in accordance with a determination that the state of the active application relates to user-to-user voice communication, the device may invoke an application for low-latency asynchronous voice communication (e.g., a walkie talkie-type function). For example, if the active application provides a voice communication interface, an extended press of the rotatable and depressible input mechanism could activate a low-latency asynchronous voice communication functionality. 
     In some embodiments, after invoking the application for low-latency asynchronous voice communication, the device receives a voice input and transmits the voice input to a second electronic device capable of receiving the voice input. As an illustrative example, in the low-latency asynchronous voice communication application, a user may speak while activating the rotatable and depressible input mechanism for an extended press, listen to a response from the second device while the rotatable and depressible input mechanism is not being activated, then speak again while activating the rotatable and depressible input mechanism for an extended press. 
     In some embodiments, in accordance with a determination that the state of the active application relates to transcribing a voice input, the device may invoke a dictation application, receive a voice input, and transcribe the voice input into a displayed text. For example, if the user is in a state of an application that receives text input (e.g., from a physical or virtual keyboard, such as a notes application), an extended press on the rotatable and depressible input mechanism may invoke a dictation application to receive instead a speech input from the user, which can be transcribed by the device into displayed text. As shown in  FIG.  6 A , device  600  has received a voice input and shows displayed text  606 , which was transcribed from the voice input. 
     In some embodiments, in accordance with a determination that the state of the active application relates to audio messaging, the device may invoke an audio messaging application, record a voice input, and send data representing the recorded voice input to a second electronic device capable of receiving the data. For example, if the user is in a text messaging application, an extended press on the rotatable and depressible input mechanism may invoke an audio messaging application to send an audio file to a recipient (e.g., a participant in a text messaging conversation). 
     In some embodiments, in accordance with a determination that the state of the active application relates to receiving a voice request to execute a task, or in accordance with a determination that the state of the current application does not relate to user-to-user voice communication or transcribing a voice input, the device may invoke a virtual assistant. Further description of a virtual assistant may be found, for example, in related application U.S. Utility application Ser. No. 12/987,982, entitled “Intelligent Automated Assistant,” filed Jan. 10, 2011 application. 
     For example, if the user is in a state of an application for executing a task, the device may invoke the virtual assistant to execute the task. Alternatively, invoking a virtual assistant may represent a default, such that the device may invoke a virtual assistant upon receiving an extended press of the rotatable and depressible input mechanism while the user is in any state of any application not explicitly assigned to invoke a different function. As described above, the functionalities invoked by an extended press of the rotatable and depressible input mechanism all relate to a speech or voice input. This unites the functions invokable through an extended press of the rotatable and depressible input mechanism by a common general feature, which helps the comprehensibility and intuitiveness of the device. Further, this allows for invoking multiple features through the same user input by determining which feature to invoke dependent upon a state of an active application. A user may be more likely to want to invoke a particular function if the user is in a state of an active application that is related to the function. 
     In some embodiments, after invoking the virtual assistant, the device displays a user interface screen on the display. This user interface screen includes a user prompt for voice input. A user prompt for voice input may include a text prompting the user to enter a voice input or an affordance representing a voice input (such as a microphone, speech balloon, or other depiction related to a voice input). As used here, the term “affordance” refers to a user-interactive graphical user interface object that may be displayed on the display screen of device  100 ,  300 , and/or  500  ( FIGS.  1 ,  3 , and  5 A ). For example, an image (e.g., icon), a virtual button, and text may each constitute an affordance. In some embodiments, the device may further receive a voice input. 
     In some embodiments, after receiving the voice input, the device transcribes the voice input into text and displays the text on the display. For example, in  FIG.  6 A , device  600  has transcribed a voice input from the user and displayed transcribed text (e.g.,  606 ) based on the voice input on the display. In some embodiments, the device also displays a waveform based on the voice input on the display (e.g., waveform  608 ). A waveform based on a voice input may graphically represent a sound wave, but it need not depict a sound wave that is precisely based on the physical characteristics of the voice input (e.g., the waveform may not be a mathematical representation of the actual sound wave of the voice input). In some embodiments, the waveform is a stylized representation of a sound wave sufficient to connote to the user that the voice input is received by the device. In some embodiments, one or more characteristics of the waveform is based on a physical characteristic of the voice input (e.g., frequency, amplitude, wave length, and so forth). 
     In some embodiments, the device displays the waveform on the display at a position adjacent to the rotatable and depressible input mechanism (e.g., a portion of the waveform is at a position proximal to the rotatable and depressible input mechanism). As shown in  FIG.  6 A , waveform  608  is displayed by device  600  at a position next to rotatable and depressible input mechanism  602 . Advantageously, this helps the user recognize that activation of the rotatable and depressible input mechanism invokes an application for receiving a voice input depicted by the waveform, thereby increasing the usability and intuitive feel of the interface through the rotatable and depressible input mechanism functionality. 
     In some embodiments, the device determines whether the voice input contains a request to execute a task executable by the virtual assistant, and in accordance with a determination that the voice input contains a request to execute a task executable by the virtual assistant, the device executes the task by the virtual assistant. Further details on this determination and tasks executed by a virtual assistant may be found in the related application cited above. 
     An embodiment of these concepts is illustrated in  FIG.  6 B .  FIG.  6 B  shows device  600  receiving a voice input with a request to text Adrian “Do you have time for coffee.” Device  600  has transcribed this voice request into displayed texts  614  and  624  on user interface screens  610  and  620 , respectively. Waveform  612  is displayed on user interface screen  610  next to rotatable and depressible input mechanism  616 . As illustrated by the transition from user interface screen  610  to user interface screen  620 , waveform  612  is animated to appear as if emanating from rotatable and depressible input mechanism  616 , as it progresses fully across the display as waveform  622  on user interface screen  620 , which is positioned next to rotatable and depressible input mechanism  626 . Similar to what was described above, this animation further strengthens the user&#39;s connection between the rotatable and depressible input mechanism itself and its functionality. 
     In some embodiments, the virtual assistant is run on the electronic device. In some embodiments, the virtual assistant is run on an external device in wireless communication with the electronic device. As used herein, invoking a virtual assistant, determining whether a voice input contains a request to execute a task executable by the virtual assistant, and/or executing a task using a virtual assistant may be performed on or by the device itself or by wirelessly communicating with one or more external devices, such as an electronic device (e.g., a phone, laptop, desktop, or tablet computer), server, and the like. For example, the device may execute a task on an external device or by using data from an external device. One or more of the functions required to execute the task (e.g., receiving a voice input, determining whether the voice input contains a request to execute a task, determining whether the task is executable by the virtual assistant, and executing the task) may be performed on an external device in wireless communication with the device (e.g., device  600 ) using data from the device and/or by sending data to the device. 
     In some embodiments, the device may send first data representing the voice input to an external device, receive from the external device second data representing a request to execute a task executable by the virtual assistant, transcribe the request into text, and display the text on the display (e.g., text  608 ,  614 , or  624 ). The device may receive the second data via wireless communication (e.g., Wi-Fi, Bluetooth™, near field communication (“NFC”), cellular and/or other wireless communication techniques, and so forth). 
     In some embodiments, the device displays an affordance representing a user prompt to display additional data related to the request on an external device. That is to say, the device may indicate to the user that additional data may be viewed on the external device, which may be particularly advantageous if the electronic device has a display smaller than the display of the external device. Additional data related to the request may include further or more detailed data requested by the user. For example, if the request is for weather information, the device may display weather information such as a predicted or current weather condition, temperature, and the like, and the user may view more detailed weather information (such as moon phase, humidity, barometric pressure, a weekly forecast, and so forth) on the external device. 
     In some embodiments, a rotatable and depressible input mechanism may include any of the functionalities described above in combination with one or more of the other functionalities described herein for a rotatable and depressible input mechanism. In some embodiments, device  600  may also include a button (e.g.,  508 ) with one or more of the functionalities described herein for a button. 
       FIG.  7    shows exemplary button functionalities for user interfaces that may be operated on device  700 . Device  700  may be device  100 ,  300 , or  500  in some embodiments. The electronic device has a display (e.g.,  504 ). As shown in  FIG.  7   , device  700  includes rotatable and depressible input mechanism  702 . The electronic device may also include a touch-sensitive surface (e.g.,  504 ) and a button (e.g.,  508 ). 
     A user may activate rotatable and depressible input mechanism  702  by activation  704 . As depicted in  FIG.  7    by the arrow block, activation  704  has an associated activation duration. In response to receiving data representing the activation, the device determines whether the activation duration exceeds a predetermined threshold. In some embodiments, the predetermined threshold is a predetermined length of time. 
     In accordance with a determination that the activation duration does not exceed the predetermined threshold (e.g., the input is a single press of rotatable and depressible input mechanism  702 , as depicted by the short, single arrow block shown for activation  704 ), the device displays a first user interface screen including a plurality of affordances on the display. For example, device  700  displays user interface screen  706  that includes a plurality of affordances that includes affordances  708  and  710 . In the plurality, at least a first affordance represents an application. For example, the affordance may be an affordance such as an icon that, when activated, causes the application to be displayed (e.g., affordances may include user-interactive icons for launching a software application). An affordance representing an application may convey to the user the application through texts, symbols, icons, depictions of an application-related screen, or any other visual indication that represents the application. In some embodiments, user interface screen  706  may be a home screen that includes a plurality of affordances representing applications. 
     While the first user interface screen is displayed, a user may activate rotatable and depressible input mechanism  702  with a second activation having a second activation duration. In response to receiving the data, the device determines whether the second activation duration exceeds a second predetermined threshold. In accordance with a determination that the second activation duration does not exceed the second predetermined threshold (e.g., the input is a single press of the rotatable and depressible input mechanism), the device displays a second user interface screen (e.g.,  720 ) that includes a clock face (e.g.,  722 ). In some embodiments, the order of screens may be reversed, such that a first single press causes the display of a clock face (e.g.,  722 ), and a second single press causes the display of a plurality of application affordances (e.g.,  708  and  710 ). Linking these functions allows the user to easily navigate between a clock face and application affordances, which is advantageous if the user uses the device to keep time and to use applications. 
     In some embodiments, the device displays a user interface screen that includes a clock face. While the user interface screen is displayed, a user may activate rotatable and depressible input mechanism  702  with a third activation having a third activation duration. In response to receiving the data, the device determines whether the third activation duration exceeds a third predetermined threshold. In accordance with a determination that the third activation duration does not exceed the third predetermined threshold (e.g., the input is a single press of the rotatable and depressible input mechanism), the device displays a second user interface screen that includes a plurality of affordances on the display. 
     In some embodiments, a rotatable and depressible input mechanism (e.g.,  702 ) is a mechanical button that is rotatable, and the activation is a physical depression of the mechanical button. In some embodiments, a rotatable and depressible input mechanism (e.g.,  702 ) is a capacitive button that is rotatable, and the activation is a touch on the capacitive button. In some embodiments, the activation (e.g.,  704 ) does not represent a rotation of the rotatable and depressible input mechanism. In some embodiments, detection of the activation is based on detecting a press such as a physical depression or a touch and does not require a rotation for detection. For example, the device may perform an action in response to an activation of  702 , and it may scroll or cycle through content or options based on the action in response to a rotation. 
     In some embodiments, a clock face displayed by the device includes a user interface object that indicates time. In some embodiments, the device displays an affordance based on the user interface object on the first user interface screen. For example, the affordance may be the same object as the user interface object but smaller, or it may be approximately the same object but with fewer details, to accommodate a smaller display size (i.e., since the affordance screen has a plurality of affordances, the affordance representing the user interface object may be smaller than the user interface object when displayed as part of a clock face). 
     In some embodiments, the user interface object and the affordance may represent a similar meaning to the user without being the same object. For example, the user interface object may be a representation of a digital clock, and the first affordance may be a representation of an analog clock. In this case, the analog clock may convey a notion of timekeeping to the user more clearly than a pair of numbers (as with a digital clock), particularly on a reduced size display. In some embodiments, the user interface object and the affordance may display the same time. In some embodiments, the user interface object and the affordance may display different times. For example, the user interface object may display a time of interest, such as a current time, whereas the affordance may display a generic time (e.g.,  10 : 10 ) as an indication to the user that activating it leads to a display of the clock face. That is to say, the affordance may simply represent the idea of timekeeping to the user so that the user recognizes that activation of the affordance displays a clock face. 
     In some embodiments, a single press of the rotatable and depressible input mechanism acts as a back button for the device, such that a single press may return the user to the most previously displayed screen in any interface of the device. 
     In some embodiments, the time indicated by the user interface object is a current time. In some embodiments, the affordance indicates a current time. 
     In some embodiments, the user interface object is a representation of an analog clock that includes an hour hand and a minute hand. In some embodiments, the user interface object is a representation of a digital clock with a numerical indication of an hour and a numerical indication of a minute. In some embodiments, the affordance is a representation of an analog clock that includes an hour hand and a minute hand. In some embodiments, the affordance is a representation of a digital clock with a numerical indication of an hour and a numerical indication of a minute. 
     In some embodiments, the predetermined threshold for the first activation duration is the same as the predetermined threshold for the second activation duration. This provides a consistent threshold to the user for interactions with the device. 
     In some embodiments, the first activation and the second activation have an associated interval of time between them, and this interval exceeds a third predetermined threshold (e.g., 0.5 seconds, 1 second, or 2 seconds). This allows the device to distinguish between sequential single presses and a double press (described below). 
     In some embodiments, a rotatable and depressible input mechanism may include any of the functionalities described above in combination with one or more of the other functionalities described herein for a rotatable and depressible input mechanism. In some embodiments, device  700  may also include a button (e.g.,  508 ) with one or more of the functionalities described herein for a button. 
       FIG.  8    shows exemplary button functionalities for user interfaces that may be operated on device  800 . Device  800  may be device  100 ,  300 , or  500  in some embodiments. The electronic device has a display (e.g.,  504 ). As shown in  FIG.  8   , device  800  includes rotatable and depressible input mechanism  802 . The electronic device may also include a touch-sensitive surface (e.g.,  504 ) and a button (e.g.,  508 ). 
     A user may activate rotatable and depressible input mechanism  802  by activation  804 . As depicted in  FIG.  8    by the arrow blocks, activation  804  has a first activation and a second activation with an associated interval between the first and the second activations. In response to receiving data representing the first and second activations, the device determines whether the interval between the first and the second activations exceeds a predetermined threshold. In some embodiments, the predetermined threshold is a predetermined length of time. 
     In accordance with a determination that the interval does not exceed the predetermined threshold (e.g., a double press, rather than two sequential single presses), the device invokes a previously invoked application.  FIG.  8    shows an application user interface screen  806  displayed by device  800  in response to double press  804  on rotatable and depressible input mechanism  802 . A previously invoked application may include any application previously invoked on the device. 
     In some embodiments, the previously invoked application is the latest invoked application that is not currently displayed. As an illustrative example, the user may invoke a calendar application, then switch to a weather application. In this example, while the weather application is displayed, the user may invoke and display the calendar application with a double press on the rotatable and depressible input mechanism. 
     In some embodiments, a rotatable and depressible input mechanism (e.g.,  802 ) is a mechanical button that is rotatable, and the first and the second activations are physical depressions of the mechanical button. In some embodiments, a rotatable and depressible input mechanism (e.g.,  802 ) is a capacitive button that is rotatable, and the first and the second activations are touches on the capacitive button. In some embodiments, the first and the second activations (e.g.,  804 ) do not include a rotation of the rotatable and depressible input mechanism. In some embodiments, detection of the activation is based on detecting a press such as a physical depression or a touch and does not require a rotation for detection. For example, in some embodiments, the device may invoke a previously invoked application by a double press of the rotatable and depressible input mechanism, then scroll or cycle through application content or other application data in response to a rotation of the rotatable and depressible input mechanism. 
     In some embodiments, the previously invoked application is invoked in an application start state. For example, in response to a double press of  802 , the device may start a previously invoked application and display the application start screen, as shown in  FIG.  8   . In some embodiments, the previously invoked application is invoked in a previous application state. In some embodiments, the previous application state corresponds to a state of the application after a user interaction. For example, if the user leaves the application in a particular state, then switches to another application, a double press of  802  would return the user to the particular state. If the user leaves the application on a particular screen, then switches to another application, a double press of  802  would return the user to the particular screen. 
     In some embodiments, the previously invoked application is invoked in a stored application state. For example, the user may save a particular state of an application and return to the state through a double press of  802 . 
     In some embodiments, a rotatable and depressible input mechanism may include any of the functionalities described above in combination with one or more of the other functionalities described herein for a rotatable and depressible input mechanism. In some embodiments, device  800  may also include a button (e.g.,  508 ) with one or more of the functionalities described herein for a button. 
       FIG.  9    shows exemplary button functionalities for user interfaces that may be operated on device  900 . Device  900  may be device  100 ,  300 , or  500  in some embodiments. The electronic device has a display (e.g.,  504 ). As shown in  FIG.  9   , device  900  includes button  902 . The electronic device may also include a touch-sensitive surface (e.g.,  504 ) and a rotatable and depressible input mechanism (e.g.,  506 ,  602 ,  702 , or  802 ). 
     A user may activate button  902  by activation  904 . As depicted in  FIG.  9    by the arrow block, activation  904  has an associated activation duration. In response to receiving data representing the activation, the device determines whether the activation duration exceeds a predetermined threshold. In some embodiments, the predetermined threshold is a predetermined length of time. 
     In accordance with a determination that the activation duration does not exceed the predetermined threshold (e.g., the input is a single press of button  902 , as depicted by the short, single arrow block shown for activation  904 ), the device displays a user interface screen that includes at least a first affordance indicating a contact from a designated list of one or more contacts, wherein the designated list is a subset of a full list of contacts on the electronic device. For example,  FIG.  9    shows user interface screen  906  that includes several affordances indicating contacts, such as affordance  908  that indicates a contact “Katie.” Contacts may be indicated by a text such as a name or an image (e.g., a user- or system-designated image associated with the contact or with a contact entry for the contact). 
     In some embodiments, a button (e.g.,  902 ) is a mechanical button, and the activation is a physical depression of the mechanical button. In some embodiments, a button (e.g.,  902 ) is a capacitive button, and the activation is a touch on the capacitive button. 
     In some embodiments, the designated list of contacts is different from other sets of contacts, such as VIPs (very important persons) or favorites. For example, in some embodiments, the designated list of contacts may be contacts with whom the user has an emotional connection. This functionality provides methods of communicating with these designated contacts (described below) that are more informal, intimate, and/or frequent than those used for other sets of contacts like VIPs, which may be a more practical set of contacts and means of communication (e.g., email). By providing these functionalities of communicating with contacts with whom the user is emotionally connected, the connection between the device and the user is strengthened and extends beyond purely productivity- or work-related functions. 
     This button functionality allows the user to quickly access a user interface screen that includes affordance(s) indicating contact(s) from a designated list of one or more contacts. It is to be noted that, in some embodiments, this screen is accessed by a single press on the button, similar to the single press on the rotatable and depressible input mechanism, which in some embodiments allows the user to access a user interface screen that includes a plurality of affordances representing application(s). These parallel functionalities enhance the usability and intuitive feel of the device by providing access to conceptual similar functionalities (e.g., a designated contacts “home screen” and an applications “home screen”) through similar types of inputs (e.g., a single press on the button and a single press on the rotatable and depressible input mechanism). 
     In some embodiments, the designated list of contacts is based on at least one of the following: time of day of interactions between the user and a contact (e.g., designated contacts may have more interactions with the user outside of typical weekday working hours relative to other contacts), frequency of interactions between the user and a contact (e.g., designated contacts may have an increased frequency of interactions with the user relative to other contacts), and length of interactions between the user and a contact (e.g., designated contacts may have longer interactions with the user relative to other contacts). 
     In some embodiments, the designated list of contacts is user-designated. For example, the device may provide a selection interface for the user to select contacts for the designated list of contacts. 
     In some embodiments, while the user interface screen is displayed, the device may receive second data representing a touch (e.g., a single press) on the touch-sensitive display at the location of an affordance corresponding to a contact. In response to receiving the second data, the device invokes a user prompt for selecting an application configured to provide a mode of interaction with the contact. 
     In some embodiments, the application configured to provide a mode of interaction with the contact is a text messaging application for sending a text to the contact. Advantageously, this functionality allows the user to quickly send a text to a designated contact without needing to enter a text messaging interface and then select the designated contact, allowing the user to interact with a designated contact more easily. In some embodiments, the application configured to provide a mode of interaction with the contact is a low-latency asynchronous voice communication application for opening low-latency asynchronous voice communication with the contact. In some embodiments, the application configured to provide a mode of interaction with the contact is an application for sending a drawing to a contact. 
     This button functionality allows the user to select a designated contact, then select a mode of interaction, rather than selecting the mode of interaction (e.g., by opening an application), then selecting the contact. Advantageously, this makes it easier for the user to interact with a contact, e.g., a contact with whom the user may frequently interact or with whom the user may be more eager to interact. That is to say, this functionality may improve the user interface with the device by allowing the user to prioritize a particular contact through quicker access to the contact, rather than forcing the user to first select the specific application for the interaction. 
     In some embodiments, while the user interface screen is displayed, the device receives third data representing a second touch on the touch-sensitive display at the location of a portion representing a contact and a third touch on the touch-sensitive display at the location of a portion representing a contact. The second and third touches are separated by an associated duration interval. In response to detecting the touches, the device determines whether the duration interval is less than a predetermined duration, and in accordance with a determination that the duration interval is less than the predetermined duration (e.g., a double touch on the portion representing the contact), the device provides an interface configured to receive data representing a user input and send a signal to a second electronic device. For example, in some embodiments, a user viewing the user interface screen may activate a display of a contact with a single tap to provide a mode of interaction with the contact (as described above), or the user may activate a display of a contact with a single tap to enter the interface. 
     The signal represents an instruction instructing the second electronic device to generate a haptic alert based on the data. In some embodiments, the user input represented by the data includes a touch on the touch-sensitive display. For example, if the data represent a series of touches on the display in a particular pattern, the haptic alert generated could be based on the particular pattern of touches. Therefore, this interface provides a way for the user to send a customizable haptic alert to a designated contact. This further reinforces the idea that the designated contacts are contacts with whom the user has an emotional connection by allowing the user to send a tangible message to the contact, even if the user and the contact are apart. 
     Attention is now directed to  FIG.  10   , which shows exemplary button functionalities for user interfaces that may be operated on device  1000 . Device  1000  may be device  100 ,  300 , or  500  in some embodiments. The electronic device has a display (e.g.,  504 ). As shown in  FIG.  10   , device  1000  includes button  1002 . The electronic device may also include a touch-sensitive surface (e.g.,  504 ) and a rotatable and depressible input mechanism (e.g.,  506 ,  602 ,  702 , or  802 ). 
     As described above, in accordance with a determination that an activation of the button is a single press, the device displays a user interface screen that includes at least a first affordance indicating a contact from a designated list of one or more contacts. In some embodiments, in accordance with a determination that the activation duration of the button activation exceeds the predetermined threshold (e.g., an extended press on the button), the device substitutes the user interface screen with a second user interface screen that includes an affordance representing a user prompt to power off the electronic device. 
     For example, as depicted in  FIG.  10   , a user may activate button  1002  by activation  1004 . As depicted by the long arrow block, activation  1004  is an extended press of button  1002 . In response to receiving data representing activation  1004 , the device displays user interface screen  1006 , which includes affordance  1008 . Affordance  1008  represents a user prompt to power off the electronic device. A user may tap, swipe, or otherwise activate affordance  1008  to power off the electronic device. 
     In some embodiments, screen  1006  also includes an affordance representing a user prompt to enter a power-saving mode of the electronic device (e.g., affordance  1010 ). In some embodiments, power-saving mode includes altering the device display (e.g., altering the color and/or brightness of one or more pixels) to reduce power consumption. In some embodiments, power-saving mode includes altering the function of one or more device components to reduce power consumption. For example, the device may alter or reduce the function of one or more RF circuitry components (such as wireless transceivers, Wi-Fi components, Bluetooth components, or other components that send and receive signals to and from external devices or servers), speakers, GPS sensor, accelerometer, directional sensor, gyroscope, motion sensor and/or other components of the device that consume power. In some embodiments, power consumption refers to battery power consumption. A user may tap, swipe, or otherwise activate affordance  1010  to enter a power-saving mode of the electronic device. 
     In some embodiments, screen  1006  also includes an affordance representing a user prompt to turn off the touch-sensitive display (e.g., affordance  1012 ). A user may tap, swipe, or otherwise activate affordance  1012  to turn off the touch-sensitive display. 
     In any of the embodiments described herein, the device may turn on the display in response to a user movement of the device (e.g., a wrist raise, lifting and/or rotation of the device, or any other indication that the user has moved the position of the device for viewing the display). As described above, the device may include various sensors, such as accelerometer  534 , gyroscope  536 , and motion sensor  538 , that may allow the device to detect a user movement of the device. These can be operatively connected to I/O section  514 , which could send a signal to the display to turn on the display. The device may also be configured to use these components to control turning off the display. In some embodiments, a lack of a specific motion input for a predetermined duration of time may cause the device to turn off the display. 
     In addition to any of these functionalities, allowing the user to further control the display through affordance  1012  is advantageous because some users may not be as capable of generating specific movements of the device configured to turn on or turn off the display. For example, if the user has interacts with or wears the device on a prosthetic limb, or uses a prosthetic limb to hold the device, the movements of the prosthetic limb may not generate the same types of movement that the device is configured to detect. Advantageously, this functionality makes the device more usable for disabled users and increases compliance with, e.g., the Americans with Disabilities Act. 
     In some embodiments, the device may be configured to detect the intensity of touches. This functionality is described in greater detail, for example, in reference to touchscreen  504  above. Techniques for detecting and processing touch intensity may be found, for example, in related applications: International Patent Application Serial No. PCT/US2013/040061, entitled “Device, Method, and Graphical User Interface for Displaying User Interface Objects Corresponding to an Application,” filed May 8, 2013 and International Patent Application Serial No. PCT/US2013/069483, entitled “Device, Method, and Graphical User Interface for Transitioning Between Touch Input to Display Output Relationships,” filed Nov. 11, 2013. 
     In some embodiments, while user interface screen  1006  is displayed, device  1000  detects a first touch on the touch-sensitive display with a first characteristic intensity. In response to detecting the first touch, the device determines whether the first characteristic intensity is above an intensity threshold. In response to a determination that the first characteristic intensity is above the intensity threshold, the device executes a separate function of the electronic device. As used here, a “separate function” of the electronic device may refer to any device function not specifically ascribed to a rotatable and depressible input mechanism interaction or a button interaction described herein. 
     In some embodiments, when the device is powered off when the extended press of the button is received, and in accordance with a determination that the activation duration of the button activation exceeds the predetermined threshold (e.g., an extended press on the button), the device powers on. As described above, an extended press on the button may serve to power on or power off the device, depending on the state of the device when the button activation is detected. 
     In some embodiments, a button may include any of the functionalities described above in combination with one or more of the other functionalities described herein for a button. In some embodiments, device  900  and/or device  1000  may also include a rotatable and depressible input mechanism (e.g.,  506 ,  602 ,  702 , or  802 ) with one or more of the functionalities described herein for a rotatable and depressible input mechanism. 
       FIG.  11    shows exemplary button functionalities for user interfaces that may be operated on device  1100 . Device  1100  may be device  100 ,  300 , or  500  in some embodiments. The electronic device has a display (e.g.,  504 ). As shown in  FIG.  11   , device  1100  includes button  1102 . The electronic device may also include a touch-sensitive surface (e.g.,  504 ) and a rotatable and depressible input mechanism (e.g.,  506 ,  602 ,  702 , or  802 ). 
     A user may activate button  1102  by activation  1104 . As depicted in  FIG.  11    by the arrow blocks, activation  1104  has a first activation and a second activation with an associated interval between the first and the second activations. In response to receiving data representing the first and second activations, the device determines whether the interval between the first and the second activations exceeds a predetermined threshold. In some embodiments, the predetermined threshold is a predetermined length of time. 
     In accordance with a determination that the interval does not exceed the predetermined threshold (e.g., a double press, rather than two sequential single presses), the device invokes a payments application. Further descriptions of exemplary payments applications may be found, for example in the related application U.S. Application Ser. No. 62/004,886, entitled “User Interface for Payments,” filed May 29, 2014. 
       FIG.  11    shows a payments application user interface screen displayed by device  1100  in response to double press  1104  on button  1102 . In some embodiments, invoking an application (e.g., a payments application) may include invoking and/or displaying an application that is already running. In some embodiments, double press  1104  may invoke a different state or screen of an already running and/or displayed application. 
     In some embodiments, the button (e.g.,  1102 ) is a mechanical button, and both of the first and the second activations represent depressions of the mechanical button. In some embodiments, the button (e.g.,  1102 ) is a capacitive button, and both of the first and the second activations represent touches on the capacitive button. 
     In some embodiments, the device displays a user interface screen that includes an affordance representing a mode of payment. In some embodiments, the mode of payment is a credit card. In some embodiments, the affordance depicts a visual representation of the face of the credit card, indicating a credit card number and a credit card company. As shown in  FIG.  11   , device  1100  displays affordance  1106 , which represents a credit card. The credit card itself is indicated by the displayed credit card company name  1108  and the displayed credit card number  1110 . In some embodiments, the credit card company and credit card number correspond to a user&#39;s credit card account. 
     In some embodiments, the mode of payment is a debit card. In some embodiments, the affordance depicts a visual representation of the face of the debit card, indicating a debit card number and a debit card bank. In some embodiments, the debit card bank and debit card number correspond to a user&#39;s debit account. 
     In some embodiments, the mode of payment is a bank account. In some embodiments, the affordance indicates at least one of a bank associated with the bank account, a type of the bank account, and a bank account number associated with the bank account. In some embodiments, the bank account is a checking account. In some embodiments, the bank account is a savings account. 
     This functionality allows the user to quickly invoke a payments application through an input (e.g., a double press of the button). It is to be noted that, in some embodiments, this application is invoked by a double press on the button, similar to the double press on the rotatable and depressible input mechanism, which in some embodiments allows the user to invoke a previously invoked application. These parallel functionalities enhance the usability and intuitive feel of the device by providing access to conceptual similar functionalities (e.g., applications) through similar types of inputs (e.g., a double press on the button and a double press on the rotatable and depressible input mechanism). 
     In some embodiments, a button may include any of the functionalities described above in combination with one or more of the other functionalities described herein for a button. In some embodiments, device  1100  may also include a rotatable and depressible input mechanism (e.g.,  506 ,  602 ,  702 , or  802 ) with one or more of the functionalities described herein for a rotatable and depressible input mechanism. 
       FIG.  12    shows exemplary button functionalities for user interfaces that may be operated on device  1200 . Device  1200  may be device  100 ,  300 , or  500  in some embodiments. The electronic device has a display (e.g.,  504 ). As shown in  FIG.  12   , device  1200  includes button  1202  and rotatable and depressible input mechanism  1204 . The electronic device may also include a touch-sensitive surface (e.g.,  504 ). 
     A user may activate button  1202  and rotatable and depressible input mechanism  1204  by activations  1206  and  1208 , respectively. Activation  1206  has a first associated activation duration, and activation  1208  has a second associated activation duration. As depicted in  FIG.  12   , activations  1206  and  1208  are received substantially simultaneously, such that activation  1208  overlaps with activation  1206  for an overlap interval. 
     In response to receiving the data, the device determines whether the data meet predetermined criteria. In accordance with a determination that the data meet the predetermined criteria, the device reboots. In some embodiments, the reboot is a hard reboot. In some embodiments, the reboot is a soft reboot. 
     In some embodiments, the rotatable and depressible input mechanism (e.g.,  1204 ) is a mechanical button that is rotatable, and the activation of the rotatable and depressible input mechanism includes a depression of the mechanical button. In some embodiments, the rotatable and depressible input mechanism (e.g.,  1204 ) is a capacitive button that is rotatable, and the activation of the rotatable and depressible input mechanism includes a touch on the capacitive button. In some embodiments, the activation of the rotatable and depressible input mechanism (e.g.,  1208 ) does not include a rotation of the rotatable and depressible input mechanism. In some embodiments, detection of the activation is based on detecting a press such as a physical depression or a touch and does not require a rotation for detection. 
     In some embodiments, the button (e.g.,  1202 ) is a mechanical button, and the activation of the button includes a depression of the mechanical button. In some embodiments, the button (e.g.,  1202 ) is a capacitive button, and wherein the activation of the button includes a touch on the capacitive button. 
     In some embodiments, the predetermined criteria relate to the first and second activation durations. In some embodiments, device  1200  determines whether both the first and the second activation durations exceed a predetermined threshold, and in accordance with a determination that both the first and the second activation durations exceed the predetermined threshold (e.g., extended presses on button  1202  and rotatable and depressible input mechanism  1204 ), the device reboots. In some embodiments, the predetermined threshold is a predetermined length of time. 
     In some embodiments, the predetermined criteria relate to the overlap interval. In some embodiments, device  1200  determines whether overlap interval exceeds a second predetermined threshold, and in accordance with a determination that the overlap interval exceeds the second predetermined threshold (e.g., substantially simultaneous extended presses on button  1202  and rotatable and depressible input mechanism  1204 ), the device reboots. 
     In some embodiments, a button and/or a rotatable and depressible input mechanism may include any of the functionalities described above in combination with one or more of the other functionalities described herein for a button and/or a rotatable and depressible input mechanism. 
     In some embodiments, an electronic device (e.g., multifunction device  500 ) may have a rotatable and depressible input mechanism (e.g.,  602 ,  616 ,  626 ,  702 ,  802 , or  1204 ) with one of more of the associated functionalities described herein and a button (e.g.,  902 ,  1002 ,  1102 , or  1202 ) with one of more of the associated functionalities described herein. The electronic device has a display (e.g.,  504 ). The electronic device may also include a touch-sensitive surface (e.g.,  504 ). In some embodiments, the device receives data representing an activation of the rotatable and depressible input mechanism and determines whether the activation represents a single press of the rotatable and depressible input mechanism (as described above), a double press of the rotatable and depressible input mechanism (as described above), or an extended press of the rotatable and depressible input mechanism (as described above). In accordance with a determination that the activation represents a single press of the rotatable and depressible input mechanism, the device displays a first user interface screen on the display, the first user interface screen including a plurality of affordances with an affordance representing an application. In accordance with a determination that the activation represents a double press of the rotatable and depressible input mechanism, the device invokes a previously invoked application. In accordance with a determination that the activation represents an extended press of the rotatable and depressible input mechanism, the device determines a state of an active application, and in accordance with a determination of the state of the active application, the device performs an action. In some embodiments, the device receives data representing an activation of the button and determines whether the activation represents a single press of the button (as described above), a double press of the button (as described above), or an extended press of the button (as described above). In accordance with a determination that the activation represents a single press of the button, the device displays a first user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, where the designated list is a subset of a full list of contacts on the electronic device. In accordance with a determination that the activation represents a double press of the button, the device invokes a payments application. In accordance with a determination that the activation represents an extended press of the button, the device displays a second user interface screen that includes a user prompt to power off the electronic device. In some embodiments, the device receives data representing an activation of the button and an activation of the rotatable and depressible input mechanism, determines whether the data meet predetermined criteria, and in accordance with a determination that the data meet the predetermined criteria, the device reboots. 
       FIG.  13    is a flow diagram illustrating process  1300  for button functionalities for user interfaces. In some embodiments, process  1300  may be performed at an electronic device with a touch-sensitive display and a rotatable and depressible input mechanism, such as device  500  ( FIG.  5   ) or device  600  ( FIGS.  6 A and  6 B ). Some operations in method  1300  may be combined, the order of some operations may be changed, and some operations may be omitted. 
     At block  1302 , the device receives data representing an activation of the rotatable and depressible input mechanism with an associated activation duration. At block  1304 , a determination is made as to whether the activation duration exceeds a predetermined threshold. At block  1306 , a determination of a state of an active application is made. At block  1308 , in accordance with a determination that the activation duration exceeds the predetermined threshold, and in accordance with a determination of the state of the active application, the device performs an action. Optionally, at block  1308 , in accordance with a determination that the state of the active application relates to user-to-user voice communication, the device performs the action at least in part by invoking an application for low-latency asynchronous voice communication. Optionally, at block  1308 , in accordance with a determination that the state of the active application relates to transcribing a voice input, the device performs the action at least in part by invoking a dictation application, receiving a voice input, and transcribing the voice input into a displayed text. Optionally, at block  1308 , in accordance with a determination that the state of the active application relates to receiving a voice request to execute a task, or in accordance with a determination that the state of the current application does not relate to user-to-user voice communication or transcribing a voice input, the device performs the action at least in part by invoking a virtual assistant. Optionally, the device may further include any of the features described herein in reference to  FIGS.  6 A and  6 B  (e.g., device  600 ). 
     Note that details of the processes described above with respect to method  1300  ( FIG.  13   ) are also applicable in an analogous manner to the methods described below. For example, method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may include one or more of the characteristics of the various methods described above with reference to method  1300 . For brevity, these details are not repeated below. 
     It should be understood that the particular order in which the operations in  FIG.  13    have been described is exemplary and not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein, as well as excluding certain operations. For brevity, these details are not repeated here. Additionally, it should be noted that aspects of method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may be incorporated with one another. Thus, the techniques described with respect to method  1300  may be relevant to method  1400 , method  1500 , method  1600 , method  1700 , method  1800 , method  1900 , and method  2000 . 
       FIG.  14    is a flow diagram illustrating process  1400  for button functionalities for user interfaces. In some embodiments, process  1400  may be performed at an electronic device with a touch-sensitive display and a rotatable and depressible input mechanism, such as device  500  ( FIG.  5   ) or device  700  ( FIG.  7   ). Some operations in method  1400  may be combined, the order of some operations may be changed, and some operations may be omitted. 
     At block  1402 , the device receives data representing an activation of the rotatable and depressible input mechanism with an associated activation duration. At block  1404 , a determination is made as to whether the activation duration exceeds a predetermined threshold. At block  1406 , in accordance with a determination that the activation duration does not exceed the predetermined threshold, the device displays a first user interface screen including a plurality of affordances on the display. At block  1408 , while the first user interface screen is displayed, the device receives second data representing a second activation of the rotatable and depressible input mechanism with an associated second activation duration. At block  1410 , a determination is made as to whether the second activation duration exceeds a second predetermined threshold. At block  1412 , in accordance with a determination that the second activation duration does not exceed the second predetermined threshold, the device substitutes the first user interface screen with a second user interface screen that includes a clock face. Optionally, the device may further include any of the features described herein in reference to  FIG.  7    (e.g., device  700 ). 
     Note that details of the processes described above with respect to method  1400  ( FIG.  14   ) are also applicable in an analogous manner to the methods described below. For example, method  1300  ( FIG.  13   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may include one or more of the characteristics of the various methods described above with reference to method  1400 . For brevity, these details are not repeated below. 
     It should be understood that the particular order in which the operations in  FIG.  14    have been described is exemplary and not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein, as well as excluding certain operations. For brevity, these details are not repeated here. Additionally, it should be noted that aspects of method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may be incorporated with one another. Thus, the techniques described with respect to method  1400  may be relevant to method  1300 , method  1500 , method  1600 , method  1700 , method  1800 , method  1900 , and method  2000 . 
       FIG.  15    is a flow diagram illustrating process  1500  for button functionalities for user interfaces. In some embodiments, process  1500  may be performed at an electronic device with a touch-sensitive display and a rotatable and depressible input mechanism, such as device  500  ( FIG.  5   ) or device  800  ( FIG.  8   ). Some operations in method  1500  may be combined, the order of some operations may be changed, and some operations may be omitted. 
     At block  1502 , the device receives data representing a first activation of the rotatable and depressible input mechanism and a second activation of the rotatable and depressible input mechanism with an associated interval between the first and the second activations. At block  1504 , a determination is made as to whether the interval exceeds a predetermined threshold. At block  1506 , in accordance with a determination that the interval does not exceed the predetermined threshold, the device invokes a previously invoked application. Optionally, the device may further include any of the features described herein in reference to  FIG.  8    (e.g., device  800 ). 
     Note that details of the processes described above with respect to method  1500  ( FIG.  15   ) are also applicable in an analogous manner to the methods described below. For example, method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may include one or more of the characteristics of the various methods described above with reference to method  1500 . For brevity, these details are not repeated below. 
     It should be understood that the particular order in which the operations in  FIG.  15    have been described is exemplary and not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein, as well as excluding certain operations. For brevity, these details are not repeated here. Additionally, it should be noted that aspects of method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may be incorporated with one another. Thus, the techniques described with respect to method  1500  may be relevant to method  1300 , method  1400 , method  1600 , method  1700 , method  1800 , method  1900 , and method  2000 . 
       FIG.  16    is a flow diagram illustrating process  1600  for button functionalities for user interfaces. In some embodiments, process  1600  may be performed at an electronic device with a touch-sensitive display a rotatable and depressible input mechanism, and a button, such as device  500  ( FIG.  5   ), device  900  ( FIG.  9   ), or device  1000  ( FIG.  10   ). Some operations in method  1600  may be combined, the order of some operations may be changed, and some operations may be omitted. 
     At block  1602 , the device receives data representing an activation of the button with an associated activation duration. At block  1604 , a determination is made as to whether the activation exceeds a predetermined threshold. At block  1606 , in accordance with a determination that the activation does not exceed the predetermined threshold, the device displays a user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, where the designated list is a subset of a full list of contacts on the electronic device. At block  1608 , in accordance with a determination that the activation exceeds the predetermined threshold, the device substitutes the user interface screen with a second user interface screen comprising a second affordance representing a user prompt to power off the electronic device. Optionally, the device may further include any of the features described herein in reference to  FIGS.  9  and  10    (e.g., device  900  or device  1000 ). 
     Note that details of the processes described above with respect to method  1600  ( FIG.  16   ) are also applicable in an analogous manner to the methods described below. For example, method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may include one or more of the characteristics of the various methods described above with reference to method  1600 . For brevity, these details are not repeated below. 
     It should be understood that the particular order in which the operations in  FIG.  16    have been described is exemplary and not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein, as well as excluding certain operations. For brevity, these details are not repeated here. Additionally, it should be noted that aspects of method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may be incorporated with one another. Thus, the techniques described with respect to method  1600  may be relevant to method  1300 , method  1400 , method  1500 , method  1700 , method  1800 , method  1900 , and method  2000 . 
       FIG.  17    is a flow diagram illustrating process  1700  for button functionalities for user interfaces. In some embodiments, process  1700  may be performed at an electronic device with a touch-sensitive display a rotatable and depressible input mechanism, and a button, such as device  500  ( FIG.  5   ) or device  1100  ( FIG.  11   ). Some operations in method  1700  may be combined, the order of some operations may be changed, and some operations may be omitted. 
     At block  1702 , the device receives data representing a first activation of the button and a second activation of the button with an associated interval between the first and the second activations. At block  1704 , a determination is made as to whether the interval exceeds a predetermined threshold. At block  1706 , in accordance with a determination that the interval does not exceed the predetermined threshold, the device invokes a payments application. Optionally, the device may further include any of the features described herein in reference to  FIG.  11    (e.g., device  1100 ). 
     Note that details of the processes described above with respect to method  1700  ( FIG.  17   ) are also applicable in an analogous manner to the methods described below. For example, method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may include one or more of the characteristics of the various methods described above with reference to method  1700 . For brevity, these details are not repeated below. 
     It should be understood that the particular order in which the operations in  FIG.  17    have been described is exemplary and not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein, as well as excluding certain operations. For brevity, these details are not repeated here. Additionally, it should be noted that aspects of method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may be incorporated with one another. Thus, the techniques described with respect to method  1700  may be relevant to method  1300 , method  1400 , method  1500 , method  1600 , method  1800 , method  1900 , and method  2000 . 
       FIG.  18    is a flow diagram illustrating process  1800  for button functionalities for user interfaces. In some embodiments, process  1800  may be performed at an electronic device with a touch-sensitive display a rotatable and depressible input mechanism, and a button, such as device  500  ( FIG.  5   ) or device  1200  ( FIG.  12   ). Some operations in method  1800  may be combined, the order of some operations may be changed, and some operations may be omitted. 
     At block  1802 , the device receives data representing an activation of the button and an activation of the rotatable and depressible input mechanism, where the activation of the button and the activation of the rotatable and depressible input mechanism are received substantially simultaneously. At block  1804 , a determination is made as to whether the data meet predetermined criteria. At block  1806 , in accordance with the determination that the data meet the predetermined criteria, the device is rebooted. Optionally, the device may further include any of the features described herein in reference to  FIG.  12    (e.g., device  1200 ). 
     Note that details of the processes described above with respect to method  1800  ( FIG.  18   ) are also applicable in an analogous manner to the methods described below. For example, method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may include one or more of the characteristics of the various methods described above with reference to method  1800 . For brevity, these details are not repeated below. 
     It should be understood that the particular order in which the operations in  FIG.  18    have been described is exemplary and not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein, as well as excluding certain operations. For brevity, these details are not repeated here. Additionally, it should be noted that aspects of method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may be incorporated with one another. Thus, the techniques described with respect to method  1800  may be relevant to method  1300 , method  1400 , method  1500 , method  1600 , method  1700 , method  1900 , and method  2000 . 
       FIG.  19    is a flow diagram illustrating process  1900  for button functionalities for user interfaces. In some embodiments, process  1900  may be performed at an electronic device with a touch-sensitive display a rotatable and depressible input mechanism, and a button, such as device  500  ( FIG.  5   ) or device  1200  ( FIG.  12   ). Some operations in method  1900  may be combined, the order of some operations may be changed, and some operations may be omitted. 
     At block  1902 , the device receives data representing an activation of the rotatable and depressible input mechanism. At block  1902 , a determination is made as to whether the activation represents a single press, a double press, or an extended press of the rotatable and depressible input mechanism. At block  1906 , in accordance with a determination that the activation represents a single press of the rotatable and depressible input mechanism, the device displays a first user interface screen including a plurality of affordances on the display. At block  1908 , in accordance with a determination that the activation represents a double press of the rotatable and depressible input mechanism, the device invokes a previously invoked application. At block  1910 , in accordance with a determination that the activation represents an extended press of the rotatable and depressible input mechanism, the device determines a state of an active application. At block  1912 , in accordance with a determination of the state of the active application, the device performs an action. 
     Note that details of the processes described above with respect to method  1900  ( FIG.  19   ) are also applicable in an analogous manner to the methods described below. For example, method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), and method  2000  ( FIG.  20   ) may include one or more of the characteristics of the various methods described above with reference to method  1900 . For brevity, these details are not repeated below. 
     It should be understood that the particular order in which the operations in  FIG.  19    have been described is exemplary and not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein, as well as excluding certain operations. For brevity, these details are not repeated here. Additionally, it should be noted that aspects of method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may be incorporated with one another. Thus, the techniques described with respect to method  1900  may be relevant to method  1300 , method  1400 , method  1500 , method  1600 , method  1700 , method  1800 , and method  2000 . 
       FIG.  20    is a flow diagram illustrating process  2000  for button functionalities for user interfaces. In some embodiments, process  2000  may be performed at an electronic device with a touch-sensitive display a rotatable and depressible input mechanism, and a button, such as device  500  ( FIG.  5   ) or device  1200  ( FIG.  12   ). Some operations in method  2000  may be combined, the order of some operations may be changed, and some operations may be omitted. 
     At block  2002 , the device receives data representing an activation of the button. At block  2004 , a determination is made as to whether the activation represents a single press, a double press, or an extended press of the button. At block  2006 , in accordance with a determination that the activation represents a single press of the button, the device displays a first user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, where the designated list is a subset of a full list of contacts on the electronic device. At block  2008 , in accordance with a determination that the activation represents a double press of the button, the device invokes a payments application. At block  2010 , in accordance with a determination that the activation represents an extended press of the button, the device displays a second user interface screen comprising a second affordance representing a user prompt to power off the electronic device. 
     Note that details of the processes described above with respect to method  12000  ( FIG.  20   ) are also applicable in an analogous manner to the methods described below. For example, method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), and method  1900  ( FIG.  19   ) may include one or more of the characteristics of the various methods described above with reference to method  2000 . For brevity, these details are not repeated below. 
     It should be understood that the particular order in which the operations in  FIG.  20    have been described is exemplary and not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein, as well as excluding certain operations. For brevity, these details are not repeated here. Additionally, it should be noted that aspects of method  1300  ( FIG.  13   ), method  1400  ( FIG.  14   ), method  1500  ( FIG.  15   ), method  1600  ( FIG.  16   ), method  1700  ( FIG.  17   ), method  1800  ( FIG.  18   ), method  1900  ( FIG.  19   ), and method  2000  ( FIG.  20   ) may be incorporated with one another. Thus, the techniques described with respect to method  2000  may be relevant to method  1300 , method  1400 , method  1500 , method  1600 , method  1700 , method  1800 , and method  1900 . 
     In accordance with some embodiments,  FIG.  21    shows a functional block diagram of an electronic device  2100  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG.  21    are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG.  21   , an electronic device  2100  includes a display unit  2102  configured to display a graphic user interface, a rotatable and depressible input mechanism unit  2104 , and a processing unit  2106  coupled to the display unit  2102  and the rotatable and depressible input mechanism unit  2104 . In some embodiments, the processing unit  2106  includes a receiving unit  2108 , a determining unit  2110 , a performing unit  2112 , and optionally, a transmitting unit  2114 , a display enabling unit  2116 , a transcribing unit  2118 , an executing unit  2120 , and a sending unit  2122 . 
     The processing unit  2106  is configured to receive (e.g., with the receiving unit  2108 ) data representing an activation of the rotatable and depressible input mechanism unit  2104 , the activation having an associated activation duration; determine (e.g., with the determining unit  2110 ) whether the activation duration exceeds a predetermined threshold; determine (e.g., with the determining unit  2110 ) a state of an active application; and in accordance with a determination that the activation duration exceeds the predetermined threshold, and in accordance with a determination of the state of the active application, perform (e.g., with the performing unit  2112 ) an action. 
     In some embodiments, the rotatable and depressible input mechanism unit  2104  is a mechanical button that is rotatable, and the activation represents a depression of the mechanical button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2104  is a capacitive button that is rotatable, and the activation represents a touch on the capacitive button. 
     In some embodiments, the activation does not represent a rotation of the rotatable and depressible input mechanism unit  2104 . 
     In some embodiments, in accordance with a determination that the state of the active application relates to user-to-user voice communication, performing the action comprises invoking an application for low-latency asynchronous voice communication. 
     In some embodiments, the processing unit  2106  is further configured to, after invoking the application for low-latency asynchronous voice communication, receive (e.g., with the receiving unit  2108 ) a voice input; and transmit (e.g., with the transmitting unit  2114 ) the voice input to a second electronic device capable of receiving the voice input. 
     In some embodiments, in accordance with a determination that the state of the active application relates to transcribing a voice input, performing the action comprises invoking a dictation application, receiving a voice input, and transcribing the voice input into a displayed text. 
     In some embodiments, in accordance with a determination that the state of the active application relates to receiving a voice request to execute a task, or in accordance with a determination that the state of the current application does not relate to user-to-user voice communication or transcribing a voice input, performing the action comprises invoking a virtual assistant. 
     In some embodiments, the processing unit  2106  is further configured to, after invoking the virtual assistant, enable display (e.g., with the display enabling unit  2116 ) of a user interface screen on the display unit  2102 , the user interface screen including a user prompt for voice input. 
     In some embodiments, the processing unit  2106  is further configured to receive a voice input. 
     In some embodiments, the processing unit  2106  is further configured to transcribe (e.g., with the transcribing unit  2118 ) the voice input into text and enable display (e.g., with the display enabling unit  2116 ) of the text on the display unit. 
     In some embodiments, the processing unit  2106  is further configured to enable display (e.g., with the display enabling unit  2116 ) of a waveform based on the voice input on the display unit  2102  at a first position. 
     In some embodiments, the first position is adjacent to the rotatable and depressible input mechanism unit  2104 . 
     In some embodiments, the processing unit  2106  is further configured to determine (e.g., with the determining unit  2110 ) whether the third voice input comprises a request to execute a task executable by the virtual assistant and, in accordance with a determination that the third voice input comprises a request to execute a task executable by the virtual assistant, execute (e.g., with the executing unit  2120 ), by the virtual assistant, the task. 
     In some embodiments, the virtual assistant is run on the electronic device. 
     In some embodiments, the virtual assistant is run on an external device in wireless communication with the electronic device. 
     In some embodiments, the processing unit  2106  is further configured to send (e.g., with the sending unit  2122 ) first data representing the voice input to the external device; and receive (e.g., with the receiving unit  2108 ), via wireless communication, second data from the external device, the second data representing a request to execute a task executable by the virtual assistant; transcribe (e.g., with the transcribing unit  2118 ) the request into text; and enable display (e.g., with the display enabling unit  2116 ) of the text on the display unit  2102 . 
     In some embodiments, the processing unit  2106  is further configured to enable display (e.g., with the display enabling unit  2116 ) of an affordance representing a user prompt to display additional data related to the request on the external device. 
     The operations described above with reference to  FIG.  13    are, optionally, implemented by components depicted in  FIGS.  1 A- 1 B  or  FIG.  21   . For example, receiving operation  1302 , determining operations  1304  and  1306 , and performing operation  1308  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS.  1 A- 1 B . 
     In accordance with some embodiments,  FIG.  22    shows a functional block diagram of an electronic device  2200  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG.  22    are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG.  22   , an electronic device  2200  includes a display unit  2202  configured to display a graphic user interface, a rotatable and depressible input mechanism unit  2204 , and a processing unit  2206  coupled to the display unit  2202  and the rotatable and depressible input mechanism unit  2204 . In some embodiments, the processing unit  2206  includes a receiving unit  2208 , a determining unit  2210 , a display enabling unit  2212 , and a substitution enabling unit  2214 . 
     The processing unit  2206  is configured to receive (e.g., with the receiving unit  2208 ) data representing an activation of the rotatable and depressible input mechanism unit  2204 , the activation having an associated activation duration; determine (e.g., with the determining unit  2210 ) whether the activation duration exceeds a predetermined threshold; in accordance with a determination that the activation duration does not exceed the predetermined threshold, enable display (e.g., with the display enabling unit  2212 ) of a first user interface screen on the display unit  2202 , the first user interface screen including a plurality of affordances and the plurality of affordances comprising an affordance representing an application; while the first user interface screen is displayed, receive (e.g., with the receiving unit  2208 ) second data representing a second activation of the rotatable and depressible input mechanism unit  2204 , the second activation having an associated second activation duration; determine (e.g., with the determining unit  2210 ) whether the second activation duration exceeds a second predetermined threshold; and, in accordance with a determination that the second activation duration does not exceed the second predetermined threshold, enable substitution (e.g., with the substitution enabling unit  2214 ) of the display of the first user interface screen with a display of a second user interface screen, the second user interface screen including a clock face. 
     In some embodiments, the rotatable and depressible input mechanism unit  2204  is a mechanical button that is rotatable, and the first and second activations both represent a depression of the mechanical button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2204  is a capacitive button that is rotatable, and the first and the second activations both represent a touch on the capacitive button. 
     In some embodiments, the first and the second activations are not rotations of the rotatable and depressible input mechanism unit  2204 . 
     In some embodiments, the clock face includes a user interface object that indicates time, and the processing unit  2206  is further configured to enable display (e.g., with the display enabling unit  2212 ) of an affordance on the first user interface screen as part of the plurality of affordances, where the affordance indicates time, and the affordance is based on the user interface object. 
     In some embodiments, the time is current time. 
     In some embodiments, the user interface object is a representation of an analog clock comprising an hour hand and a minute hand. 
     In some embodiments, the affordance is a representation of an analog clock comprising an hour hand and a minute hand. 
     In some embodiments, the first and second predetermined thresholds are the same. 
     In some embodiments, the first activation and the second activation have an associated interval between the first and the second activations and the interval exceeds a third predetermined threshold. 
     The operations described above with reference to  FIG.  14    are, optionally, implemented by components depicted in  FIGS.  1 A- 1 B  or  FIG.  22   . For example, receiving operations  1402  and  1408 , determining operations  1404  and  1410 , displaying operation  1406 , and substituting operation  1412  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS.  1 A- 1 B . 
     In accordance with some embodiments,  FIG.  23    shows a functional block diagram of an electronic device  2300  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG.  23    are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG.  23   , an electronic device  2300  includes a display unit  2302  configured to display a graphic user interface, a rotatable and depressible input mechanism unit  2304 , and a processing unit  2306  coupled to the display unit  2302  and the rotatable and depressible input mechanism unit  2304 . In some embodiments, the processing unit  2306  includes a receiving unit  2308 , a determining unit  2310 , and an invoking unit  2312 . 
     The processing unit  2306  is configured to receive (e.g., with the receiving unit  2308 ) first data representing a first activation of the rotatable and depressible input mechanism unit  2304  and a second activation of the rotatable and depressible input mechanism unit  2304 , the first and the second activations having an associated interval between the first and the second activations; in response to receiving the first data, determine (e.g., with the determining unit  2310 ) whether the interval between the first and the second activations exceeds a predetermined threshold; and in accordance with a determination that the interval does not exceed the predetermined threshold, invoke (e.g., with the invoking unit  2312 ) a previously invoked application. 
     In some embodiments, the rotatable and depressible input mechanism unit  2304  is a mechanical button that is rotatable, and both of the first and the second activations represent depressions of the mechanical button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2304  is a capacitive button that is rotatable, and both of the first and the second activations represent touches on the capacitive button. 
     In some embodiments, the first and the second activations do not comprise a rotation of the rotatable and depressible input mechanism unit  2304 . 
     In some embodiments, the previously invoked application is invoked in an application start state. 
     In some embodiments, the previously invoked application is invoked in a previous state. 
     In some embodiments, the previous state corresponds to a state of the application after a user interaction. 
     In some embodiments, the previous state corresponds to a stored state of the application. 
     In some embodiments, the previously invoked application is a latest invoked application that is not currently displayed. 
     The operations described above with reference to  FIG.  15    are, optionally, implemented by components depicted in  FIGS.  1 A- 1 B  or  FIG.  23   . For example, receiving operation  1502 , determining operation  1504 , and invoking operation  1506  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS.  1 A- 1 B . 
     In accordance with some embodiments,  FIG.  24    shows a functional block diagram of an electronic device  2400  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG.  24    are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG.  24   , an electronic device  2400  includes a display unit  2402  configured to display a graphic user interface, a touch-sensitive surface unit  2404  configured to receive contacts, a rotatable and depressible input mechanism unit  2406 , a button unit  2408  and a processing unit  2410  coupled to the display unit  2402 , the touch-sensitive surface unit  2404 , the rotatable and depressible input mechanism unit  2406 , and the button unit  2408 . In some embodiments, the processing unit  2410  includes a receiving unit  2412 , a determining unit  2414 , a display enabling unit  2416 , and optionally, an invoking unit  2418 , a providing unit  2420 , a sending unit  2422 , a substitution enabling unit  2424 , a detecting unit  2426 , an executing unit  2428 , and a powering unit  2430 . 
     The processing unit  2410  is configured to receive (e.g., with the receiving unit  2412 ) first data representing an activation of the button unit  2408  the activation having an associated activation duration; determine (e.g., with the determining unit  2414 ) whether the activation duration exceeds a predetermined threshold; and in accordance with a determination that the activation duration does not exceed the predetermined threshold, enable display (e.g., with the display enabling unit  2416 ) of a user interface screen, the user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, where the designated list is a subset of a full list of contacts on the electronic device. 
     In some embodiments, the button unit  2408  is a mechanical button, and the activation represents a depression of the mechanical button. 
     In some embodiments, the button unit  2408  is a capacitive button, and the activation represents a touch on the capacitive button. 
     In some embodiments, the designated list of contacts is based on at least one of the following: time of day of interactions between the user and a contact, frequency of interactions between the user and a contact, and length of interactions between the user and a contact. 
     In some embodiments, the designated list of contacts is user-designated. 
     In some embodiments, the processing unit  2410  is further configured to, while the user interface screen is displayed, receive (e.g., with the receiving unit  2412 ) second data representing a touch on the touch-sensitive surface unit  2404  at the location of an affordance corresponding to a contact; and in response to receiving the second data, invoke (e.g., with the invoking unit  2418 ) a user prompt for selecting an application configured to provide a mode of interaction with the contact. 
     In some embodiments, the application is a text messaging application. 
     In some embodiments, the application is a low-latency asynchronous voice communication application. 
     In some embodiments, the application is an application for sending a drawing to the contact. 
     In some embodiments, the processing unit  2410  is further configured to, while the user interface screen is displayed, receive (e.g., with the receiving unit  2412 ) third data representing a second touch on the touch-sensitive surface unit  2404  and a third touch on the touch-sensitive surface unit  2404  separated by an associated duration interval, where both the second and third touches are at the location of a portion representing a contact; determine (e.g., with the determining unit  2414 ) whether the duration interval is less than a predetermined duration; and in accordance with a determination that the duration interval is less than the predetermined duration, provide (e.g., with the providing unit  2420 ) an interface, the interface configured to receive (e.g., with the receiving unit  2412 ) fourth data representing a user input; and send (e.g., with the sending unit  2422 ) a signal to a second electronic device, the signal representing an instruction instructing the second electronic device to generate a haptic alert based on the fourth data. 
     In some embodiments, the user input represented by the fourth data comprises a touch on the touch-sensitive surface unit  2404 . 
     In some embodiments, the processing unit  2410  is further configured to, in accordance with a determination that the activation duration exceeds the predetermined threshold, enable substitution (e.g., with the substitution enabling unit  2424 ) of the first user interface screen with a second user interface screen, the second user interface screen comprising a second affordance representing a user prompt to power off the electronic device. 
     In some embodiments, the second user interface screen further comprises a third affordance representing a user prompt to enter a power-saving mode of the electronic device. 
     In some embodiments, the second user interface screen further comprises a fourth affordance representing a user prompt to turn off the touch-sensitive surface unit  2404 . 
     In some embodiments, the touch-sensitive surface unit  2404  is configured to detect the intensity of touches, and the processing unit  2410  is further configured to, while the second user interface screen is displayed, detect (e.g., with the detecting unit  2426 ) a first touch on the touch-sensitive surface unit  2404 , the first touch having a first characteristic intensity; determine (e.g., with the determining unit  2414 ) whether the first characteristic intensity is above an intensity threshold; and in response to a determination that the first characteristic intensity is above the intensity threshold, execute (e.g., with the executing unit  2428 ) a separate function of the electronic device. 
     In some embodiments, the electronic device is powered off when the first data are received, and in accordance with a determination that the activation duration exceeds the predetermined threshold, the processing unit  2410  further configured to power (e.g., with the powering unit  2430 ) on the electronic device. 
     The operations described above with reference to  FIG.  16    are, optionally, implemented by components depicted in  FIGS.  1 A- 1 B  or  FIG.  24   . For example, receiving operation  1602 , determining operation  1604 , displaying operation  1606 , and substituting operation  1608  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS.  1 A- 1 B . 
     In accordance with some embodiments,  FIG.  25    shows a functional block diagram of an electronic device  2500  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG.  25    are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG.  25   , an electronic device  2500  includes a display unit  2502  configured to display a graphic user interface, a touch-sensitive surface unit  2504  configured to receive contacts, a rotatable and depressible input mechanism unit  2506 , a button unit  2508  and a processing unit  2510  coupled to the display unit  2502 , the touch-sensitive surface unit  2504 , the rotatable and depressible input mechanism unit  2506 , and the button unit  2508 . In some embodiments, the processing unit  2506  includes a receiving unit  2512 , a determining unit  2514 , an invoking unit  2516 , and optionally, a display enabling unit  2518 . 
     The processing unit  2510  is configured to receive (e.g., with the receiving unit  2512 ) first data representing a first activation of the button unit  2508  and a second activation of the button unit  2508 , the first and the second activations having an associated interval between the first and the second activations; determine (e.g., with the determining unit  2514 ) whether the interval between the first and the second activations exceeds a predetermined threshold; and in accordance with a determination that the interval does not exceed the predetermined threshold, invoke (e.g., with the invoking unit  2516 ) a payments application. 
     In some embodiments, the button unit  2508  is a mechanical button, and both of the first and the second activations represent depressions of the mechanical button. 
     In some embodiments, the button unit  2508  is a capacitive button, and both of the first and the second activations represent touches on the capacitive button. 
     In some embodiments, the processing unit  2510  is further configured to enable display (e.g., with the display enabling unit  2518 ) of a user interface screen on the display unit  2502 , the user interface screen including an affordance, the affordance representing a mode of payment. 
     In some embodiments, the mode of payment is a credit card. 
     In some embodiments, the affordance comprises a visual representation of the face of the credit card, the visual representation indicating a credit card number and a credit card company. 
     In some embodiments, the mode of payment is a debit card. 
     In some embodiments, the affordance comprises a visual representation of the face of the debit card, the visual representation indicating a debit card number and a debit card bank. 
     In some embodiments, the mode of payment is a bank account. 
     In some embodiments, the affordance indicates at least one of a bank associated with the bank account, a type of the bank account, and a bank account number associated with the bank account. 
     The operations described above with reference to  FIG.  17    are, optionally, implemented by components depicted in  FIGS.  1 A- 1 B  or  FIG.  25   . For example, receiving operation  1702 , determining operation  1704 , and invoking operation  1706  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS.  1 A- 1 B . 
     In accordance with some embodiments,  FIG.  26    shows a functional block diagram of an electronic device  2600  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG.  26    are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG.  26   , an electronic device  2600  includes a display unit  2602  configured to display a graphic user interface, a touch-sensitive surface unit  2604  configured to receive contacts, a rotatable and depressible input mechanism unit  2606 , a button unit  2608  and a processing unit  2610  coupled to the display unit  2602 , the touch-sensitive surface unit  2604 , the rotatable and depressible input mechanism unit  2606 , and the button unit  2608 . In some embodiments, the processing unit  2106  includes a receiving unit  2612 , a determining unit  2614 , and a rebooting unit  2616 . 
     The processing unit  2610  is configured to receive (e.g., with the receiving unit  2612 ) data representing an activation of the button unit  2608  and an activation of the rotatable and depressible input mechanism unit  2606 , where the activation of the button unit  2608  has a first associated activation duration, the activation of the rotatable and depressible input mechanism unit  2606  has a second associated activation duration and overlaps with the activation of the button unit  2608  for an overlap interval, and the activation of the button unit  2608  and the activation of the rotatable and depressible input mechanism unit  2606  are received substantially simultaneously; determine (e.g., with the determining unit  2614 ) whether the data meet predetermined criteria; and in accordance with a determination that the data meet the predetermined criteria, reboot (e.g., with the rebooting unit  2616 ) the electronic device. 
     In some embodiments, the rotatable and depressible input mechanism unit  2606  is a mechanical button that is rotatable, and the activation of the rotatable and depressible input mechanism unit  2606  comprises a depression of the mechanical button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2606  is a capacitive button that is rotatable, and the activation of the rotatable and depressible input mechanism unit  2606  comprises a touch on the capacitive button. 
     In some embodiments, the activation of the rotatable and depressible input mechanism unit  2606  does not comprise a rotation of the rotatable and depressible input mechanism unit  2606 . 
     In some embodiments, the button unit  2608  is a mechanical button, and the activation of the button unit  2608  comprises a depression of the mechanical button. 
     In some embodiments, the button unit  2608  is a capacitive button, and the activation of the button unit  2608  comprises a touch on the capacitive button. 
     In some embodiments, the predetermined criteria relate to the first and second activation durations, and the processing unit  2610  is further configured to determine (e.g., with the determining unit  2614 ) whether both the first and the second activation durations exceed a predetermined threshold; and, in accordance with a determination that both the first and the second activation durations exceed the predetermined threshold, reboot (e.g., with the rebooting unit  2616 ) the electronic device. 
     In some embodiments, the predetermined criteria relate to the overlap interval, and the processing unit  2610  is further configured to determine (e.g., with the determining unit  2614 ) whether overlap interval exceeds a second predetermined threshold, and, in accordance with a determination that the overlap interval exceeds the second predetermined threshold, reboot (e.g., with the rebooting unit  2616 ) the electronic device. 
     The operations described above with reference to  FIG.  18    are, optionally, implemented by components depicted in  FIGS.  1 A- 1 B  or  FIG.  26   . For example, receiving operation  1802 , determining operation  1804 , and rebooting operation  1806  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS.  1 A- 1 B . 
     In accordance with some embodiments,  FIG.  27    shows a functional block diagram of an electronic device  2700  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG.  27    are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG.  27    an electronic device  2700  includes a display unit  2702  configured to display a graphic user interface, a touch-sensitive surface unit  2704  configured to receive contacts, a rotatable and depressible input mechanism unit  2706 , a button unit  2708  and a processing unit  2710  coupled to the display unit  2702 , the touch-sensitive surface unit  2704 , the rotatable and depressible input mechanism unit  2706 , and the button unit  2708 . In some embodiments, the processing unit  2706  includes a receiving unit  2712 , a determining unit  2714 , a display enabling unit  2716 , an invoking unit  2718 , a performing unit  2720 , and optionally, a substitution enabling unit  2722 , a transmitting unit  2724 , a transcribing unit  2726 , an executing unit  2728 , and a sending unit  2730 . 
     The processing unit  2710  is configured to receive (e.g., with the receiving unit  2712 ) first data representing an activation of the rotatable and depressible input mechanism unit  2706 ; determine (e.g., with the determining unit  2714 ) whether the activation represents a single press of the rotatable and depressible input mechanism unit  2706 , the single press having an associated press duration, a double press of the rotatable and depressible input mechanism unit  2706 , the double press having an associated interval between a first press of the rotatable and depressible input mechanism unit  22706  and a second press of the rotatable and depressible input mechanism unit  2706 , the first and the second presses of the rotatable and depressible input mechanism unit  2706  each having an associated press duration, or an extended press of the rotatable and depressible input mechanism unit  2706 , the extended press having an associated press duration; and, in accordance with a determination that the activation represents a single press of the rotatable and depressible input mechanism unit  2706 , enable display (e.g., with the display enabling unit  2716 ) of a first user interface screen on the display unit  2702 , the first user interface screen including a plurality of affordances, the plurality of affordances comprising an affordance representing an application; in accordance with a determination that the activation represents a double press of the rotatable and depressible input mechanism unit  2706 , invoke (e.g., with the invoking unit  2718 ) a previously invoked application; and in accordance with a determination that the activation represents an extended press of the rotatable and depressible input mechanism unit  2706 , determine (e.g., with the determining unit  2714 ) a state of an active application and in accordance with a determination of the state of the active application, perform (e.g., with the performing unit  2720 ) an action. 
     In some embodiments, the processing unit  2710  is further configured to receive (e.g., with the receiving unit  2712 ) second data representing an activation of the button unit  2708 ; determine (e.g., with the determining unit  2714 ) whether the activation represents a single press of the button unit  2708 , the single press having an associated press duration, a double press of the button unit  2708 , the double press having an associated interval between a first press of the button unit  2708  and a second press of the button unit  2708 , the first and the second presses of the button unit  2708  each having an associated press duration; or an extended press of the button unit  2708 , the extended press having an associated press duration; and in accordance with a determination that the activation represents a single press of the button unit  2708 , enable display (e.g., with the display enabling unit  2716 ) of a third user interface screen, the third user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, where the designated list is a subset of a full list of contacts on the electronic device; in accordance with a determination that the activation represents a double press of the button unit  2708 , invoke (e.g., with the invoking unit  2718 ) a payments application; and in accordance with a determination that the activation represents an extended press of the button unit  2708 , enable display (e.g., with the display enabling unit  2716 ) of a fourth user interface screen including a second affordance representing a user prompt to power off the electronic device. 
     In some embodiments, the rotatable and depressible input mechanism unit  2706  is a mechanical button that is rotatable, and the single press or the extended press of the rotatable and depressible input mechanism unit  2706  comprises a depression of the mechanical button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2706  is a mechanical button that is rotatable, and the double press of the rotatable and depressible input mechanism unit  2706  comprises a first and a second depression of the mechanical button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2706  is a capacitive button that is rotatable, and the single press or the extended press of the rotatable and depressible input mechanism unit  2706  comprises a touch on the capacitive button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2706  is a capacitive button that is rotatable, and the double press of the rotatable and depressible input mechanism unit  2706  comprises a first and a second touch on the capacitive button. 
     In some embodiments, the activation does not comprise a rotation of the rotatable and depressible input mechanism unit  2706 . 
     In some embodiments, the button unit  2708  is a mechanical button, and the single press or the extended press of the button unit  2708  comprises a depression of the mechanical button. 
     In some embodiments, the button unit  2708  is a mechanical button, and the double press of the button unit  2708  comprises a first and a second depression of the mechanical button. 
     In some embodiments, the button unit  2708  is a capacitive button, and the single press or the extended press of the button unit  2708  comprises a touch on the capacitive button. 
     In some embodiments, the button unit  2708  is a capacitive button, and the double press of the button unit  2708  comprises a first and a second touch on the capacitive button. 
     In some embodiments, determining whether the activation represents a single press of the rotatable and depressible input mechanism unit  2706  comprises determining whether the press duration of the single press exceeds a first predetermined threshold; and, in accordance with a determination that the press duration of the single press does not exceed the first predetermined threshold, determining whether third data is received within a second interval after receiving the first data, the third data representing an activation of the rotatable and depressible input mechanism unit  2706 ; and in accordance with a determination that the third data is not received within the second interval, determining that the activation represents a single press of the rotatable and depressible input mechanism unit  2706 . 
     In some embodiments, the processing unit  2710  is further configured to, in accordance with the determination that the activation represents a single press of the rotatable and depressible input mechanism unit  2706 , and while the first user interface screen is displayed, receive (e.g., with the receiving unit  2712 ) fourth data representing a second single press of the rotatable and depressible input mechanism unit  2706 ; and in response to receiving the fourth data, enable substitution (e.g., with the substitution enabling unit  2722 ) of the display of the first user interface screen with a display of a fifth user interface screen, the fifth user interface screen including a clock face. 
     In some embodiments, the clock face includes a first user interface object that indicates time, and the processing unit  2710  is further configured to enable display (e.g., with the display enabling unit  2716 ) of a third affordance on the fifth user interface screen as part of the plurality of affordances, where the third affordance indicates the time, and the third affordance is based on the first user interface object. 
     In some embodiments, the time is current time. 
     In some embodiments, the first user interface object is a representation of an analog clock comprising an hour hand and a minute hand. 
     In some embodiments, the third affordance is a representation of an analog clock including an hour hand and a minute hand. 
     In some embodiments, determining whether the activation represents a double press of the rotatable and depressible input mechanism unit  2706  comprises determining whether the press duration of the first press of the double press exceeds a second predetermined threshold; in accordance with a determination that the press duration of the first press of the double press does not exceed the second predetermined threshold, determining whether the interval between the first press of the double press and the second press of the double press exceeds a third predetermined threshold; in accordance with a determination that the interval between the first press of the double press and the second press of the double press does not exceed the third predetermined threshold, determining whether the press duration of the second press of the double press exceeds a fourth predetermined threshold; and in accordance with a determination that the press duration of the second press of the double press does not exceed the second predetermined threshold, determining that the activation represents a double press of the rotatable and depressible input mechanism unit  2706 . 
     In some embodiments, the second and the fourth predetermined thresholds are the same. 
     In some embodiments, in accordance with the determination that the activation represents a double press of the rotatable and depressible input mechanism unit  2706 , the previously invoked application is invoked in an application start state. 
     In some embodiments, in accordance with the determination that the activation represents a double press of the rotatable and depressible input mechanism unit  2706 , the previously invoked application is invoked in a previous state. 
     In some embodiments, in accordance with the determination that the activation represents a double press of the rotatable and depressible input mechanism unit  2706 , the previous state corresponds to a state of the application after a user interaction. 
     In some embodiments, in accordance with the determination that the activation represents a double press of the rotatable and depressible input mechanism unit  2706 , the previous state corresponds to a stored state of the application. 
     In some embodiments, the previously invoked application is a latest invoked application that is not currently displayed. 
     In some embodiments, determining whether the activation represents an extended press of the rotatable and depressible input mechanism unit  2706  comprises determining whether the press duration of the extended press exceeds a fifth predetermined threshold; and, in accordance with a determination that the press duration of the extended press exceeds the fifth predetermined threshold, determining that the activation represents an extended press of the rotatable and depressible input mechanism unit  2706 . 
     In some embodiments, in accordance with the determination that the activation represents an extended press of the rotatable and depressible input mechanism unit  2706 , and in accordance with a determination that the state of the active application relates to user-to-user voice communication, performing the action comprises invoking an application for low-latency asynchronous voice communication. 
     In some embodiments, the processing unit  2710  is further configured to, after invoking the application for low-latency asynchronous voice communication, receive (e.g., with the receiving unit  2712 ) a second voice input and transmit (e.g., with the transmitting unit  2724 ) the second voice input to a second electronic device capable of receiving the second voice input. 
     In some embodiments, in accordance with the determination that the activation represents an extended press of the rotatable and depressible input mechanism unit  2706 , and in accordance with a determination that the state of the active application relates to transcribing a voice input, performing the action comprises invoking a dictation application; receiving a voice input; and transcribing the voice input into a displayed text. 
     In some embodiments, in accordance with the determination that the activation represents an extended press of the rotatable and depressible input mechanism unit  2706 ; and, in accordance with a determination that the state of the active application relates to receiving a voice request to execute a task, or in accordance with a determination that the state of the current application does not relate to user-to-user voice communication or transcribing a voice input, performing the action comprises invoking a virtual assistant. 
     In some embodiments, the processing unit  2710  is further configured to, after invoking the virtual assistant, enable display (e.g., with the display enabling unit  2716 ) of a sixth user interface screen on the display unit  2702 , the sixth user interface screen including a user prompt for voice input. 
     In some embodiments, the processing unit  2710  is further configured to receive (e.g., with the receiving unit  2712 ) a voice input. 
     In some embodiments, the processing unit  2710  is further configured to transcribe (e.g., with the transcribing unit  2726 ) the voice input into text and enable display (e.g., with the display enabling unit  2716 ) of the text on the display unit  2702 . 
     In some embodiments, the processing unit  2710  is further configured to enable display (e.g., with the display enabling unit  2716 ) of a waveform based on the voice input on the display unit  2702  at a first position. 
     In some embodiments, the first position is adjacent to the rotatable and depressible input mechanism unit  2706 . 
     In some embodiments, the processing unit  2710  is further configured to determine (e.g., with the determining unit  2714 ) whether the voice input comprises a request to execute a task executable by the virtual assistant and, in accordance with a determination that the voice input comprises a request to execute a task executable by the virtual assistant, execute (e.g., with the executing unit  2728 ), by the virtual assistant, the task. 
     In some embodiments, the virtual assistant is run on the electronic device. 
     In some embodiments, the virtual assistant is run on an external device in wireless communication with the electronic device. 
     In some embodiments, the processing unit  2710  is further configured to send (e.g., with the sending unit  2730 ) fifth data representing the voice input to the external device; receive (e.g., with the receiving unit  2712 ), via wireless communication, sixth data from the external device, the sixth data representing a request to execute a task executable by the virtual assistant; transcribe (e.g., with the transcribing unit  2726 ) the request into text; and enable display (e.g., with the display enabling unit  2716 ) of the text on the display unit  2702 . 
     In some embodiments, the processing unit  2710  is further configured to enable display (e.g., with the display enabling unit  2716 ) of a fourth affordance representing a user prompt to display additional data related to the request on the external device. 
     The operations described above with reference to  FIG.  19    are, optionally, implemented by components depicted in  FIGS.  1 A- 1 B  or  FIG.  27   . For example, receiving operation  1902 , determining operations  1904  and  1910 , displaying operation  1906 , invoking operation  1908 , and performing operation  1912  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS.  1 A- 1 B . 
     In accordance with some embodiments,  FIG.  28    shows a functional block diagram of an electronic device  2800  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG.  28    are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG.  28   , an electronic device  2800  includes a display unit  2802  configured to display a graphic user interface, a touch-sensitive surface unit  2804  configured to receive contacts, a rotatable and depressible input mechanism unit  2806 , a button unit  2808  and a processing unit  2810  coupled to the display unit  2802 , the touch-sensitive surface unit  2804 , the rotatable and depressible input mechanism unit  2806 , and the button unit  2808 . In some embodiments, the processing unit  2806  includes a receiving unit  2812 , a determining unit  2814 , a display enabling unit  2816 , an invoking unit  2818 , and optionally, a performing unit  2820 , a detecting unit  2822 , an executing unit  2824 , and a sending unit  2826 . 
     The processing unit  2810  is configured to receive (e.g., with the receiving unit  2812 ) first data representing an activation of the button unit  2808 ; determine (e.g., with the determining unit  2814 ) whether the activation represents a single press of the button unit  2808 , the single press having an associated press duration, a double press of the button unit  2808 , the double press having an associated interval between a first consecutive press and a second consecutive press, the first and second consecutive presses each having an associated press duration, or an extended press of the button unit  2808 , the extended press having an associated press duration; and in accordance with a determination that the activation represents a single press of the button unit  2808 , enable display (e.g., with the display enabling unit  2816 ) of a first user interface screen, the first user interface screen including at least a first affordance indicating a contact from a designated list of one or more contacts, where the designated list is a subset of a full list of contacts on the electronic device; in accordance with a determination that the activation represents a double press of the button unit  2808 , invoke (e.g., with the invoking unit  2818 ) a payments application; and in accordance with a determination that the activation represents an extended press of the button unit  2808 , enable display (e.g., with the display enabling unit  2816 ) of a second user interface screen, the second user interface screen comprising a second affordance representing a user prompt to power off the electronic device. 
     In some embodiments, the processing unit  2810  is further configured to receive (e.g., with the receiving unit  2812 ) second data representing an activation of the rotatable and depressible input mechanism unit  2806 ; determine (e.g., with the determining unit  2814 ) whether the activation represents a single press of the rotatable and depressible input mechanism unit  2806 , the single press having an associated press duration, a double press of the rotatable and depressible input mechanism unit  2806 , the double press having an associated interval between a first consecutive press and a second consecutive press, the first and second consecutive presses each having an associated press duration, or an extended press of the rotatable and depressible input mechanism unit  2806 , the extended press having an associated press duration; and in accordance with a determination that the activation represents a single press of the rotatable and depressible input mechanism unit  2806 , enable display (e.g., with the display enabling unit  2816 ) of a third user interface screen on the display unit  2802 , the third user interface screen including a plurality of affordances, the plurality of affordances comprising an affordance representing an application; in accordance with a determination that the activation represents a double press of the rotatable and depressible input mechanism unit  2806 , invoke (e.g., with the invoking unit  2818 ) a previously invoked application; and in accordance with a determination that the activation represents an extended press of the rotatable and depressible input mechanism unit  2806 , determine (e.g., with the determining unit  2814 ) a state of an active application; and in accordance with a determination of the state of the active application, perform (e.g., with the performing unit  2820 ) an action. 
     In some embodiments, the button unit  2808  is a mechanical button, and the single press or the extended press of the button unit  2808  comprises a depression of the mechanical button. 
     In some embodiments, the button unit  2808  is a mechanical button, and the double press of the button unit  2808  comprises a first and a second depression of the mechanical button. 
     In some embodiments, the button unit  2808  is a capacitive button, and the single press or the extended press of the button unit  2808  comprises a touch on the capacitive button. 
     In some embodiments, the button unit  2808  is a capacitive button, and the double press of the button unit  2808  comprises a first and a second touch on the capacitive button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2806  is a mechanical button that is rotatable, and the single press or the extended press of the rotatable and depressible input mechanism unit  2806  comprises a depression of the mechanical button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2806  is a mechanical button that is rotatable, and the double press of the rotatable and depressible input mechanism unit  2806  comprises a first and a second depression of the mechanical button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2806  is a capacitive button that is rotatable, and the single press or the extended press of the rotatable and depressible input mechanism unit  2806  comprises a touch on the capacitive button. 
     In some embodiments, the rotatable and depressible input mechanism unit  2806  is a capacitive button that is rotatable, and the double press of the rotatable and depressible input mechanism unit  2806  comprises a first and a second touches on the capacitive button. 
     In some embodiments, the activation does not comprise a rotation of the rotatable and depressible input mechanism unit  2806 . 
     In some embodiments, determining whether the activation represents a double press of the button unit  2808  comprises determining whether the press duration of the first press of the double press exceeds a first predetermined threshold; in accordance with a determination that the press duration of the first press of the double press does not exceed the first predetermined threshold, determining whether the interval between the first press of the double press and the second press of the double press exceeds a second predetermined threshold; in accordance with a determination that the interval between the first press of the double press and the second press of the double press does not exceed the second predetermined threshold, determining whether the press duration of the second press of the double press exceeds a third predetermined threshold; and in accordance with a determination that the press duration of the second press of the double press does not exceed the third predetermined threshold, determining that the activation represents a double press of the button unit  2808 . 
     In some embodiments, the first and the third predetermined thresholds are the same. 
     In some embodiments, the processing unit  2810  is further configured to, in accordance with the determination that the activation represents a double press of the button unit  2808 , and after invoking the payments application, enable display (e.g., with the display enabling unit  2816 ) of a fifth user interface screen on the display unit  2802 , the fifth user interface screen including a fifth affordance, the fifth affordance representing a mode of payment. 
     In some embodiments, the mode of payment is a credit card. 
     In some embodiments, the fifth affordance comprises a visual representation of the face of the credit card, the visual representation indicating a credit card number and a credit card company. 
     In some embodiments, the mode of payment is a debit card. 
     In some embodiments, the fifth affordance comprises a visual representation of the face of the debit card, the visual representation indicating a debit card number and a debit card bank. 
     In some embodiments, the mode of payment is a bank account. 
     In some embodiments, the fifth affordance indicates at least one of a bank associated with the bank account, a type of the bank account, and a bank account number associated with the bank account. 
     In some embodiments, determining whether the activation represents an extended press of the button unit  2808  comprises determining whether the press duration of the extended press exceeds a fourth predetermined threshold; and, in accordance with a determination that the press duration of the extended press exceeds the fourth predetermined threshold, determining that the activation represents an extended press of the button unit  2808 . 
     In some embodiments, the processing unit  2810  is further configured to enable display (e.g., with the display enabling unit  2816 ) of a sixth user interface screen comprising a sixth affordance representing a user prompt to power off the electronic device. 
     In some embodiments, the sixth user interface screen further comprises a seventh affordance representing a user prompt to enter a power-saving mode of the electronic device. 
     In some embodiments, the sixth user interface screen further comprises an eighth affordance representing a user prompt to turn off the touch-sensitive surface unit. 
     In some embodiments, the touch-sensitive surface unit is configured to detect the intensity of touches, and the processing unit  2810  is further configured to, while the sixth user interface screen is displayed, detect (e.g., with the detecting unit  2822 ) a first touch on the touch-sensitive surface unit, the first contact having a first characteristic intensity; determine (e.g., with the determining unit  2814 ) whether the first characteristic intensity is above an intensity threshold; and in response to a determination that the first characteristic intensity is above the intensity threshold, execute (e.g., with the executing unit  2824 ) a separate function of the electronic device. 
     In some embodiments, in accordance with a determination that the activation represents an extended press of the button unit  2808 , where the electronic device is powered off when the first data are received, and the processing unit  2810  is further configured to power on the electronic device. 
     In some embodiments, determining whether the activation represents a single press of the button unit  2808  comprises determining whether the press duration of the single press exceeds a fifth predetermined threshold; and in accordance with a determination that the press duration of the single press does not exceed the fifth predetermined threshold, determining whether second data is received within a second interval after receiving the first data, the second data representing an activation of the button unit  2808 ; and in accordance with a determination that the second data is not received within the second interval, determining that the activation represents a single press of the button unit  2808 . 
     In some embodiments, the processing unit  2810  is further configured to, in accordance with the determination that the activation represents a single press of the button unit  2808 , and while the first user interface screen is displayed, automatically compile the designated list of contacts based on at least one of the following: time of day of interactions between a user and a contact, frequency of interactions between a user and a contact, and length of interactions between a user and a contact. 
     In some embodiments, the designated list of contacts is user-designated. 
     In some embodiments, the processing unit  2810  is further configured to, while the first user interface screen is displayed, receive third data representing a touch on the touch-sensitive surface unit at the location of a first affordance indicating a contact; and in response to receiving the third data, invoke (e.g., with the invoking unit  2818 ) a user prompt for selecting an application configured to provide a mode of interaction with the indicated contact. 
     In some embodiments, the application is a text messaging application. 
     In some embodiments, the application is a low-latency asynchronous voice communication application. 
     In some embodiments, the application is an application for sending a drawing to the indicated contact. 
     In some embodiments, the processing unit  2810  is further configured to, in accordance with the determination that the activation represents a single press of the button unit  2808 , and while the first user interface screen is displayed receive (e.g., with the receiving unit  2812 ) fourth data representing a second touch on the touch-sensitive surface unit and a third touch on the touch-sensitive surface unit separated by an associated duration interval, where both the second and third touches are at the location of a portion representing a contact; determine (e.g., with the determining unit  2814 ) whether the duration interval is less than a sixth predetermined duration; and in accordance with a determination that the duration interval is less than the sixth predetermined duration, provide an interface, the interface configured to receive (e.g., with the receiving unit  2812 ) fifth data representing a user input and send (e.g., with the sending unit  2826 ) a signal to a second electronic device, the signal representing an instruction instructing the second electronic device to generate a haptic alert based on the fifth data. 
     In some embodiments, the user input represented by the fifth data comprises a touch on the touch-sensitive surface unit. 
     The operations described above with reference to  FIG.  20    are, optionally, implemented by components depicted in  FIGS.  1 A- 1 B  or  FIG.  2   . For example, receiving operation  2002 , determining operation  2004 , displaying operations  2004  and  2010 , and invoking operation  2008  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS.  1 A- 1 B . 
     The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the techniques and their practical applications. Others skilled in the art are thereby enabled to best utilize the techniques and various embodiments with various modifications as are suited to the particular use contemplated. 
     Although the disclosure and examples have been fully described with reference to the accompanying figures, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the appended claims.