通知中心
Notification Center was released in iOS 5 to replace the previous system for dealing with push and local notifications. Instead of interrupting the user with an alert, Notification Center instead displays a banner at the top of the screen. This allows the user to continue using their device, and disappears after a set period of time. All previous notifications are collated into the Notification Center panel, which can be displayed in iOS by dragging down from the status bar, and in macOS by clicking on the notification center icon to the very right on the menu bar at the top of the screen (or using track-pad gestures, swiping from right to left). Notifications may be selected by the user, which redirects the user to the application where the notification was initially created, and marking that alert as read. Once a notification is read, it is removed from the panel. Users may also remove notifications without reading them by deleting individual alerts, or dismissing all of an application's alerts from within the application that is generating them. When an iOS device is locked, new notifications appear on the lock screen, and users may access the application generating the alert by swiping the application's icon with their finger from left to right along the notification.