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780aabbc9676-0 | Adopt a Widget
Contributions
How to contribute
Discord
Guidelines
Ways to contribute
Adding code
Snippets
Sample
DartPad sample
Adding References
Adding more explanation to the documentation
Quickstart
Get the code
Open the code in your IDE
Make the change
Analyzing and Generating API Docs
Commit the change
Make a pull request
Resources
Note:
The Adopt a Widget program ran during the month of
November 2020. Thanks so much for your participation!
We may do something similar in the future. | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-1 | Flutter is an open source project hosted on GitHub
and the API docs (generated from the source code) are
hosted on api.flutter.dev.
Adopting a widget and improving its documentation helps everyone!
So, for the month of November, we’re extending a special
invitation to contribute to the Flutter project by choosing
a Widget and improving its API documentation.
Contributions
(Updated Feb 14, 2021)
Chinmay-KB contributed to the
WillPopScope docs
(pull request)
chihempat contributed to the
SliverWithKeepAliveWidget docs
(pull request)
obitodarky contributed to the
Stepper docs
(pull request)
Sameerkash found an issue with the StatusTransitionWidget docs (issue)
tadaspetra contributed to the
MaterialBanner docs
(pull request) | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-2 | tadaspetra contributed to the
MaterialBanner docs
(pull request)
IsmailAbdirahman contributed to the
NotificationListener docs
(pull request)
Aneesh Rao contributed to the
CircularProgressIndicator docs
(pull request)
Abhishek Ghaskata contributed to the
Hero docs
(pull request)
singhsuryanshu contributed to the
FittedBox docs
(pull request)
parzuko contributed to the
Draggable docs
(pull request)
Oscar Robles contributed to the
ActionListener docs
(pull request)
arps18 contributed to the
Shortcuts docs
(pull request)
Sanjoli Goyal contributed to the
ReorderableListView docs
(pull request)
Amitpatil215 contributed to the
AspectRatio docs
(pull request)
CaptainIRS contributed to the
AbsorbPointer docs
(pull request) | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-3 | CaptainIRS contributed to the
AbsorbPointer docs
(pull request)
Yazeed AlKhalaf contributed to the
IgnorePointer docs
(pull request)
abd99 contributed to the
Dismissible docs
(pull request)
Mitesh Singh contributed to the
PageView docs
(pull request)
redsolver contributed to the
Table docs
(pull request)
tsvillain contributed to the
Tooltip docs
(pull request)
Thesmader contributed to the
SnackBar docs
(pull request)
Muskan Jain contributed to the
ColorFiltered docs
(pull request)
Sergio Eric contributed to the
PreferredSizeWidget docs
(pull request)
How to contribute
Go to this list of issues and choose one.
You can only be assigned one Adopt A Widget issue at a
time, so choose your favorite! | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-4 | Leave a comment on the issue, asking to be assigned.
The first person to respond will be assigned. For example:
Once you are assigned, set up your environment, make the change,
and submit the pull request. If you’re not sure how to do this,
see the Quickstart guide below.
The CONTRIBUTING
doc has details on contributing to Flutter.
Discord
Join the #AdoptAWidget channel on the Flutter Discord server
to ask questions and get help.
Guidelines
Wait to be assigned
If you aren’t assigned to the issue, let the assignee fix it.
Don’t submit a pull request for someone else’s issue.
Respond within three days after being assigned
If we don’t hear back from you,
we might need to assign it to someone else.
One issue at a time | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-5 | One issue at a time
If you’re already working on an issue,
wait until it’s closed before requesting another.
Don’t create “Adopt A Widget” issues
We are limiting AdoptAWidget to this list of issues.
Don’t worry if you don’t get assigned
There are plenty of other issues that can be fixed.
You can also take a look for
issues with the “d: api docs” label
that need attention.
Be original
Don’t copy code snippets or text from other sources like StackOverflow.
Ways to contribute
Each issue specifies what type of contribution we are looking for:
Adding code (either a snippet, sample, or DartPad)
Adding references (for example, under “See also”)
Adding more explanation to the documentation
Adding code | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-6 | Adding more explanation to the documentation
Adding code
There are three ways to contribute code: a snippet,
a dartpad, or a sample.
For more details, see the Dartdoc Generation README.
Please be cognizant that writing sample code has a different goal
(and some additional constraints) compared to writing production code.
Mozilla has a good overview (the article is about the web,
but 95% of it applies to any platform).
Snippets
Snippets can be added using the following syntax:
/// {@tool snippet}
///
/// This is a comment explaining the snippet below:
///
/// ```dart
/// MyWidget(
/// color: Colors.green,
/// )
/// ```
/// {@end-tool}
Sample | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-7 | /// ```
/// {@end-tool}
Sample
Samples are snippets of code that are wrapped with a template,
so you don’t have to write boilerplate code.
The --template can be any of the templates found in
the snippet tool’s templates directory.
/// {@tool sample --template=stateless_widget_scaffold_center}
///
/// This is a comment explaining the snippet below:
///
/// ```dart
/// Widget build(BuildContext context) {
/// return MyWidget(
/// color: Colors.green,
/// );
/// }
/// ```
/// {@end-tool}
DartPad sample | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-8 | /// {@end-tool}
DartPad sample
To add a sample that runs in DartPad,
use {@tool dartpad} and provide the same
templates found in the templates directory:
/// {@tool dartpad --template=stateless_widget_material}
///
/// This is a comment explaining the snippet below:
///
/// ```dart
/// Widget build(BuildContext context) {
/// return MyWidget(
/// color: Colors.green,
/// );
/// }
/// ```
/// {@end-tool}
Adding References
If a Widget needs references,
add a See also: section to the end of a widget’s
documentation comment:
/// Creates a route for the given route settings.
/// | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-9 | /// Creates a route for the given route settings.
///
/// Used by [Navigator.onGenerateRoute].
///
/// See also:
///
/// * [Navigator], which is where all the [Route]s end up.
Adding more explanation to the documentation
If a widget doesn’t provide enough explanation,
you can add more! You can explain:
What it is
What it enables you to do
How to use it
The behavior of the widget in certain situations
Other important information about the widget
See the documentation section of the Flutter Style Guide
and Effective Dart - Documentation
for details on how to write great documentation.
Quickstart
Use the following instructions to get started.
Get the code | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-10 | Use the following instructions to get started.
Get the code
To get started,
fork the SDK and use git to fetch a local copy:
Install dependencies listed in
Setting up the Framework development environment.
Fork the Flutter repo. For more information,
see GitHub’s official instructions.
Clone your fork:
`git clone https://github.com//flutter.git`</nobr>
Change directory into the repo: cd flutter
Add an upstream remote:
`git remote add upstream git@github.com:flutter/flutter.git`
Run flutter update-packages to fetch all the Dart packages that
Flutter uses.
Open the code in your IDE
In IntelliJ or VSCode, open packages/flutter,
where most of the Flutter framework code lives.
Make the change | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-11 | Make the change
Open the file listed in the issue and update the documentation.
See “Ways to contribute” for examples.
Analyzing and Generating API Docs
Running this command from the root directory analyzes
and generates the documentation. This command can
take up to 20 minutes to complete, so double
check your changes first. If you want, you can also
analyze snippets directly.
To view the generated docs, open dev/docs/doc/api/index.html.
Note:
Flutter API docs cannot be generated on Windows.
If you are using Windows, you may need to download
the Linux version of the SDK and use the
Windows Subsystem for Linux.
For more information, see the Dartdoc Generation README.
Commit the change
Modify the documentation and commit the change:
b update-builder-widget
git add
A
git commit
m | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-12 | A
git commit
m
"Update Builder API Docs"
git push origin update-builder-widget
Make a pull request
Make a pull request with
AdoptAWidget: WidgetName in the title,
and fill out this template:
<!-- Provide an explanation of the change -->
<!-- Specify what this pull request does -->
This pull request is:
[x] A code sample
[ ] More references
[ ] More explanation
<!-- Add the AdoptAWidget issue that is assigned to you: -->
closes #1234
Note:
If you are a first-time contributor to this repo,
you will be asked to sign Google’s
Contributor License Agreement.
Resources
Setting up the Framework development environment
CONTRIBUTING
Dartdoc Generation README | https://docs.flutter.dev/adoptawidget/index.html |
780aabbc9676-13 | CONTRIBUTING
Dartdoc Generation README
Flutter Style Guide - Documentation
Effective Dart - Documentation | https://docs.flutter.dev/adoptawidget/index.html |
7ef9fa334f60-0 | Fall 2021 Flutter Apprentice event
The Flutter Apprentice event has ended.
Thanks to all who participated!
If you missed the event, you can purchase
the Flutter Apprentice book from
raywenderlich.com, and watch the free
book club replay videos.
Book club replay videos
You can find replays of the book club videos on YouTube.
Chapters covered
Topic
Video replay
1, 2
Getting started
week 1 replay
3, 4
Widgets
week 2 replay
5, 6
More widgets
week 3 replay
7, 8
Navigation
week 4 replay
9, 15 | https://docs.flutter.dev/apprentice-giveaway/index.html |
7ef9fa334f60-1 | week 4 replay
9, 15
Data persistence
week 5 replay
10, 11
Networking & serialization
week 6 replay
12, 14
Chopper & streams
week 7 replay
13
State management
week 8 replay
19
Firebase
week 9 replay
16, 17, 18
Deployment
week 10 replay | https://docs.flutter.dev/apprentice-giveaway/index.html |
d01d7ce9d703-0 | Flutter Brand Guidelines
General Rules That Govern the Use of the Flutter Trademarks
Specific Rules for Proper Usage of the Flutter Trademarks
Community Use Exceptions
The “Flutter” name and logo are trademarks owned by Google.
These Brand Guidelines describe the appropriate uses of the Flutter
trademarks by members of the developer community who have obtained our
consent to use the trademarks pursuant to the Flutter Terms of Service.
These guidelines will ensure that the Flutter trademarks are used in a
manner that promotes Google’s mission to provide a free and open source
SDK for crafting high-quality native interfaces on iOS and
Android in record time, and are not associated with objectionable material,
as determined by Google.
Use of the Flutter trademarks that is not expressly permitted by these
guidelines is prohibited absent written permission from Google. | https://docs.flutter.dev/brand/index.html |
d01d7ce9d703-1 | The official Flutter assets and further guidelines on representing the brand
can be found at Representing the Flutter Brand.
General Rules That Govern the Use of the Flutter Trademarks
You are free to use the Flutter trademarks: (i) in connection with your
download and use of the Flutter SDK to build and develop
apps, (ii) in training materials (e.g., video tutorials, online publications,
etc.) that provide instructions or tips regarding how to use the Flutter
SDK to build and develop apps, and (iii) to show your support for
the use of the Flutter SDK by members of the developer community.
These guidelines do not restrict your right to use the “Flutter” name
in connection with descriptions of the Flutter SDK that would be
considered “fair use.” For example, you may use the “Flutter”
name to make truthful factual statements (e.g., “built with the Flutter
SDK”) or to accurately describe a feature of the Flutter SDK. | https://docs.flutter.dev/brand/index.html |
d01d7ce9d703-2 | You may use the Flutter trademarks on your personal website, personal
blog, or social media account to show your support for the Flutter SDK,
provided you do not use the Flutter trademarks in a way that
could confuse people into thinking that your site is an official Google
site or that Google has sponsored or endorsed your site. In the case of
websites or personal blogs, this means you should not use the Flutter
trademarks as the primary element on the webpage (e.g., in the masthead
of the webpage or the title of the blog). In the case of social media
accounts, this means you should not use the Flutter trademarks in the
background, in your profile image or in your social media username.
Specific Rules for Proper Usage of the Flutter Trademarks
In addition to the general rules discussed above, below are specific
rules governing the proper use of the Flutter trademarks.
DO: | https://docs.flutter.dev/brand/index.html |
d01d7ce9d703-3 | DO:
Use the “Flutter” name as an adjective, never as a noun or verb,
and never in the plural or possessive form.
Use a generic term following the “Flutter” name, for example,
“the Flutter SDK” or “the Flutter UI toolkit.”
Distinguish the “Flutter” name from the surrounding text in some way.
Capitalize the first letter, capitalize or italicize the entire mark,
place the mark in quotes, use a different type style or font for the mark.
Use the trademark symbol TM for the first or most prominent
time the “Flutter” name appears in text on your website or blog.
Make sure to always use the TM symbol,
not the ® symbol.
Include the following text near the first or most prominent use of the
Flutter marks on your website or blog: “Flutter and the related logo are
trademarks of Google LLC. We are not endorsed by or affiliated with
Google LLC.” | https://docs.flutter.dev/brand/index.html |
d01d7ce9d703-4 | Keep some distance between the Flutter trademarks and any other trademarks,
logos, or icons that are displayed on the webpage.
DON’T:
Don’t alter, distort, or modify the Flutter trademarks in any way.
This includes varying the spelling of the “Flutter” name, or displaying
the Flutter logo with color variations or unapproved visual elements.
Don’t combine the Google name with the “Flutter” name to form a unitary
brand (e.g., don’t use the phrases “Google Flutter” or “Google’s Flutter”).
You may use the Google name in full text to accurately describe the
Flutter SDK (e.g., “The Flutter SDK by Google”).
Don’t register the Flutter trademarks or any trademarks, logos,
or domain names that are confusingly similar to them. | https://docs.flutter.dev/brand/index.html |
d01d7ce9d703-5 | Don’t incorporate the Flutter trademarks into your own product names,
service names, trademarks, logos, or company names.
Don’t display the Flutter trademarks in a manner that is misleading,
unfair, defamatory, infringing, libelous, disparaging, obscene or
otherwise objectionable to Google.
Don’t use the Flutter trademarks on or in connection with the sale of
any non-software goods or services (e.g., merchandise such as clothing,
pens, and stickers).
Community Use Exceptions
To allow for the use of the Flutter trademarks by the Flutter community,
below are specific exceptions to the rules described above: | https://docs.flutter.dev/brand/index.html |
d01d7ce9d703-6 | Local Flutter user groups may: (i) use the “Flutter” name
as part of their social media username in the following format:
“Flutter + [name of country/city]” (e.g., “Flutter France”); and (ii)
use the Flutter logo in the national colors of the country where the
user group is based (e.g., for a user group based in France,
the colors blue, white and red), provided the Flutter logo is otherwise
unaltered. Such social media accounts should include a disclaimer that
clarifies that it is not an official Google account. | https://docs.flutter.dev/brand/index.html |
d01d7ce9d703-7 | You may use the Flutter trademarks as part of the name of a newsletter
or related community content (e.g., Flutter training courses,
Flutter community forums) whose purpose is to promote the use of the
Flutter SDK by members of the developer community.
Where the Flutter trademarks are displayed on a website as part of a
community site name, you should use the trademark symbol TM
after the most prominent appearance of the “Flutter” name and include
the following text: “Flutter and the related logo are trademarks of
Google LLC. We are not endorsed by or affiliated with Google LLC.”
Where the Flutter trademarks are displayed on a social media account
as part of a community site name, you should include a disclaimer that
clarifies that it is not an official Google account. | https://docs.flutter.dev/brand/index.html |
d01d7ce9d703-8 | [Unofficial Flutter Events] You may use the Flutter trademarks as part of the name
of a community event (e.g. conference), but please make sure to include the following disclaimer
on the event website in a prominent and easy-to-see spot: “Flutter and the related logo are trademarks of Google LLC.
[Title of event] is not affiliated with or otherwise sponsored by Google LLC.” | https://docs.flutter.dev/brand/index.html |
fbbe27f7bffb-0 | Looking for inspiration?
See examples of what developers built with Flutter!
Flutter Clock Challenge
Share #FlutterClock with friends
Watch video
Results
Create a beautiful clock face UI
Build a beautiful clock face UI with Flutter for the Lenovo Smart Clock for a chance to win an iMac Pro,
Lenovo Smart Display, or Lenovo Smart Clock.
Submissions period has ended on January 20, 2020. Please scroll down to see the results.
Flutter Clock Highlight Reel
Flutter Clock contest is brought to you in partnership with Google Assistant and Lenovo.
All Winners
Check out
this article to read more about this year's results.
Grand Prize Winner
Particle Clock by Mickel Andersson
Category Winners | https://docs.flutter.dev/clock/index.html |
fbbe27f7bffb-1 | Particle Clock by Mickel Andersson
Category Winners
Visual Beauty
Cloom Clock
by Filipe Barroso and Francisco Frutuoso
Code Quality
Creative Creator Or Maybe Not Clock
by Hubert Henkemeier
Overall Execution
Humanbeans Clock
by Boris Brestnichki
Novelty
Sunset Reflections Clock by Victor Morilla
Honorable Mentions
Agent Clock by Thomas Krueger
Animal Clock by Sei Lee
Ants Clock by Pau Picas Sans
BarBar Clock by Aleksandr Troshkov
Boating Clock by Yi He
Circle Clock by Max Bowser
DJ Clock by Bao Hui Huang | https://docs.flutter.dev/clock/index.html |
fbbe27f7bffb-2 | DJ Clock by Bao Hui Huang
Dots Clock by Tran Duy Khanh Steffen
Flutter Clock by Dezso Meszaros
Flutter Clock by Dominik Roszkowski
Flutter Clock by Helge Wieding
Flutter Clock by Masayuki Ono
Flutter Clock by Vyacheslav Ryabinin
Freehand Clock by Tyler Hayes
Generative Clock by Fabian Stein
Infinity Clock by Akash Divya
Iso Clock by Scott Cook
Lofi Clock by Michael Wilson
Matches Clock by Mikołaj Lenart
Paper Clock by Ryan Taylor
Scenery Clock by Valerii Kuznietsov
Snake Clock by Gilles Devillers | https://docs.flutter.dev/clock/index.html |
fbbe27f7bffb-3 | Snake Clock by Gilles Devillers
Star Clock by Philipp Bauer
Steampunk Clock by Roman Cinis
Tetris Time Clock by Michael Jentsch | https://docs.flutter.dev/clock/index.html |
508c079ecf33-0 | Explicit animations
What are explicit animations?
Animation concepts
What is animation?
Example: bouncing ball (starter code 1)
Frame rate
Example: bouncing ball (starter code 2)
Interpolation
Example: bouncing ball (starter code 3)
AnimationController
What is an AnimationController?
Create your first explicit animation with AnimationController
1. Use a TickerProvider mixin
2. Instantiate and dispose of AnimationController in lifecycle methods
3. Pass AnimationController parameters
4. Add listener(s)
5. Trigger the animation
AnimationController concepts
The Animation object
AnimationController interpolates frame values
AnimationController doesn’t know anything about the UI
Curves
Tweens
AnimatedBuilder
AnimatedWidget | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-1 | Tweens
AnimatedBuilder
AnimatedWidget
Welcome to the explicit animations codelab,
where you learn how to create animations
with more complex and custom features
than can be achieved using implicit animations.
Note:
This codelab is not yet complete.
Note:
This codelab uses embedded DartPads to display examples and exercises.
If you see empty boxes instead of DartPads, check out
Troubleshooting DartPad.
To get the most out of this codelab,
you should have basic knowledge of the following:
How to make a Flutter app.
How to use stateful widgets.
This codelab covers the following material:
Animation concepts
Using AnimationController to implement explicit animations
Choosing between implicit and explicit animations
What are explicit animations? | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-2 | Choosing between implicit and explicit animations
What are explicit animations?
Explicit animations are a set of controls for
telling Flutter how to rapidly rebuild the widget tree
while changing widget properties to create animation effects.
This approach enables you to create effects that you can’t achieve
using implicit animations.
Animation concepts
Learning to create explicit animations can be daunting
if you are new to animation in general.
The following section equips you with animation concepts
that help you better grasp how explicit
animations work in Flutter.
The subsequent sections relate these concepts
to the corresponding tools and methods of explicit animations.
If you are already experienced with animation, you can skip this
section and move on to the AnimationController section.
What is animation? | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-3 | What is animation?
Think about how animations work
in a flip-book, or cartoons on TV, or a movie reel.
What do these animation technologies have in common?
They create the illusion of motion by rapidly transitioning
a single frame that you are viewing to other frames
within a pre-defined sequence.
Suppose you want to create your own Flutter animation
without using the animations library.
Start with the simplest case possible:
Your goal is to animate a ball
so that it repeatedly bounces up and down.
The following example demonstrates a first attempt
using a naive approach.
Can you spot the lines of code that create the effect?
Example: bouncing ball (starter code 1) | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-4 | Example: bouncing ball (starter code 1)
The preceding example uses the container’s margin property
to alternate the position of the ball on the screen,
and a periodic timer to control
how frequently the ball changes its position (once every second).
As a viewer, this approach leaves a lot to be desired.
The ball only has two positions,
so the animation looks pretty choppy—you could
easily mistake the animation for a glitch.
To describe this problem in animation terms,
you would say that the animation alternates
between only two frames:
Note:
In this example, you are creating an animation effect
that only looks like it is running at two frames per second.
In reality, Flutter is running this example at ~60 frames per second.
frame #
position
movement direction
top margin: 0
top margin: 100
down
top margin: 0
up | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-5 | down
top margin: 0
up
Most importantly, this example demonstrates at a basic
level how frames are used to create animations:
A frame is a single still image that can be used
within a sequence of other still images
to create the illusion of motion.
In this case, the first frame consists of a
ball centered on the screen,
and the second frame consists of the same ball
placed further down on the screen using
the top margin property.
PENDING: # image: a frame in Flutter | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-6 | PENDING: # image: a frame in Flutter
Even this though example doesn’t use Flutter’s
animation library, it creates an animation
in fundamentally the same way:
by telling Flutter to rebuild its widget tree
so as to rapidly move between frames
over a specified period of time.
This is an important takeaway to keep in mind
while creating explicit animations.
At a fundamental level,
explicit animations provide you with controls
for telling Flutter how to quickly rebuild a widget tree
to create the illusion of motion. You’ll learn more
about these controls later in this codelab.
Given what you’ve learned so far,
can you think of a way to improve the bouncing ball effect
in the preceding example?
Try to come up with an answer before diving into the next section.
Quick review:
A frame is a single still image that can be used
within a sequence of other still images
to create the illusion of motion. | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-7 | In Flutter, you can think of a single frame as
a static configuration of a widget tree.
An animation is a sequence of frames that,
when rapidly displayed over time,
creates the illusion of motion.
In Flutter, an animation changes a widget property value
between frames to create the illusion of motion.
You can create an animation by telling Flutter
to rapidly rebuild a widget tree while gradually
changing a widget property on each iteration
of the widget tree.
The first example uses a timer to trigger
a change in the top margin of the bouncing ball
once every second.
Frame rate | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-8 | Frame rate
The previous example represents a naive approach
to animating a bouncing ball:
it alternates the position of the ball
between only two frames,
switching frames once every second.
One way to improve this animation is to use more frames,
which smoothes out the animation
and provides a more convincing illusion of movement.
Consider what changes you need to make to the example
so that, instead of having just two positions,
the ball has five:
frame #
position
movement direction
top margin: 0
top margin: 25
down
top margin: 50
down
top margin: 75
down
top margin: 100
down
top margin: 75
up
top margin: 50
up | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-9 | up
top margin: 50
up
top margin: 25
up
top margin: 0
up
Now that you are using more frames,
in order to keep the ball bouncing at the same rate
(one bounce per second)
you need to increase the frame rate.
The frame rate is the rate of frames per second (fps).
In this case, you are increasing the frame rate
from 2 frames per second to 4 fps.
Even though you are using five total frames,
the first frame gets re-used for the downward and upward
motion of the ball,
so you only need to count it once
for the purpose of determining the frame rate. | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-10 | Now that you have increased the frame rate
for this animation,
you can also calculate the new value that
the margin should change in each frame.
As the preceding chart makes clear,
now that there are 5 frames instead of 2,
and since the top margin value remains
between 0 and 100 throughout the animation,
each frame either increases or decreases
the ball’s top margin value by 25.
Change in margin value between each
frame = total change in margin / # of frames
In this case, the top margin changes by 100
over 4 frames, so each frame
changes the top margin value by 25.
(Even though there are 5 total frames,
in this example you are reusing one frame for both
the downward and upward motion of the ball, so you
only need to count 4 frames for the margin change.) | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-11 | That’s it! With the updated frame rate
and the top margin values needed for each frame,
you now have enough information
to update the preceding example
by doubling the frame rate that the animation uses.
Before diving into the following example,
think about how you might refactor the preceding example
using these updated parameters.
You can use the DartPad editor in the preceding example
to try out your solution.
When you’re ready, run the next example to
view the updated animation:
Example: bouncing ball (starter code 2)
Quick Review:
Frame rate is measured as the number of frames per second (fps).
Flutter aims to provide 60 fps performance,
or 120 fps performance on devices capable of 120Hz updates.
For 60fps, frames need to render approximately every 16ms.
See performance profiling page for more information.
Interpolation | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-12 | Interpolation
Have you ever wondered how computer graphics animators
draw each and every frame of your favorite CGI movies?
Well, they don’t! Instead, animators set an initial
position and a final position for the object they are animating.
Next, they rely on software to compute all of the
positions for the object between the initial and the
final position that they defined.
The process of computing animation values between
a starting and ending position is called interpolation.
As a developer, interpolation vastly simplifies
how you reason about and create your animations.
Instead of thinking of an animation
in terms of hundreds (or thousands) of frames,
you can think of an animation
as a starting value and an ending value,
and allow interpolation to take care of the rest! | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-13 | The preceding example uses an imperative approach for
calculating the values for each frame
in the animation:
you explicitly provide
values for the frame rate as well as
the value needed to increment
the top margin property for each frame.
Can you think of a way to refactor this example
so that you only need to provide a starting and ending
value for top margin, and leave the rest to an
interpolation function the generates the values
for the frames in between?
Here’s a few hints:
Don’t worry about animating the ball
up and down. Just focus on the first downward motion
of the ball (from a top margin of 0 to top margin of 100).
Try using 60 fps for the frame rate.
For any starting or ending position of the ball,
you can express the amount to increment top margin
between each frame as the difference between the margin’s
starting and ending values divided by the total number of frames. | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-14 | The following example contains one way to implement these updates
to the bouncing ball example. Run the example to the see the difference
that these updates make to your animation:
Example: bouncing ball (starter code 3)
At 60 fps, this updated version of the bouncing ball animation
looks smoother than in all prior examples!
This example only creates half of the animation—the
ball moves down, but not back up again.
Wouldn’t it be nice to have a declarative interface
for controlling the direction that the animation proceeds
across the sequence of frames, and the conditions for
starting and stopping it? This way, you could easily
represent when to start the animation, pause it,
play forward, play backward, end it, or repeat it indefinitely.
In the next section, you’ll learn how Flutter’s animation library
provides an interface for doing all of these things.
Quick review: | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-15 | Quick review:
Interpolation is the process of computing all animation values
between a starting and ending value.
Instead of thinking about an animation in terms of hundreds (or thousands)
of frames, interpolation allows you to reason about and define an animation
in terms of its starting and ending value.
Bonus questions!
In the prior example, the rate of change for the
bouncing ball’s top margin value is linear
(the margin changes by the same amount between each frame).
How would you change this example to make it possible to
interpolate values between 0 and 100 at a changing rate?
The prior example only animates a single downward motion
of the bouncing ball. Can you think of a way to:
Continue the animation so that the ball bounces back up again?
Repeat the animation indefinitely?
AnimationController | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-16 | AnimationController
The AnimationController is a special Animation
object that generates a new value whenever the hardware
is ready for a new frame. All explicit
animations require an AnimationController.
What is an AnimationController?
Whether the animation should progress forward or backward
through the range of values once triggered.
The amount(s) that an animation’s value changes between each frame.
The following sections demonstrate how to use
AnimationController by providing step-by-step instructions for
creating your first explicit animation with
AnimationController[] and by covering the
underlying concepts of AnimationController.
Create your first explicit animation with AnimationController
The following example begins with no animation code—it
consists of a Material app home screen containing a green ball shape.
PENDING: Insert DartPad here | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-17 | PENDING: Insert DartPad here
This section provides guided steps for building
the same bouncing ball animation
created in the Animation concepts section—
the difference is that this example uses an explicit animation,
whereas the animation concepts section
uses a naive approach in order to introduce
fundamental animation concepts.
PENDING : bouncing ball example
Use the following instructions to create an explicit animation
of a bouncing ball:
1. Use a TickerProvider mixin
{explicit1 → explicit2}/lib/main.dart
@@ -9,7 +9,8 @@
9
9
State<BouncingBallDemo> createState() => _BouncingBallDemoState();
10
10
11
class _BouncingBallDemoState extends State<BouncingBallDemo> {
11 | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-18 | 11
+
class _BouncingBallDemoState extends State<BouncingBallDemo>
12
+
with SingleTickerProviderStateMixin {
12
13
@override
13
14
void initState() {
14
15
super.initState();
This step uses the SingleTickerProviderStateMixin
with _BouncingBallDemoState,
but you can also use TickerProviderStateMixin to make your widget
available as a TickerProvider for AnimationController.
Here are some considerations for deciding between the two:
If you are only creating a single AnimationController
from a State object (as in this example)
you can use the SingleTickerProviderStateMixin. | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-19 | If you need to create more than one AnimationController
over the lifetime of a State object,
use the TickerProviderStateMixin instead.
The SingleTickerProviderStateMixin is slightly more efficient
than TickerProviderStateMixin in the case of the class
only ever needing one Ticker.
2. Instantiate and dispose of AnimationController in lifecycle methods
Instantiate AnimationController in a widget lifecycle method,
and call the AnimationController.dispose() within the
State.dispose() lifecycle method:
{explicit2 → explicit3}/lib/main.dart
@@ -1,3 +1,5 @@
+
// ignore_for_file: missing_required_argument
1
3
import 'dart:async';
2
4
import 'package:flutter/material.dart'; | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-20 | 2
4
import 'package:flutter/material.dart';
@@ -11,9 +13,12 @@
11
13
class _BouncingBallDemoState extends State<BouncingBallDemo>
12
14
with SingleTickerProviderStateMixin {
15
+
late AnimationController controller;
16
13
17
@override
14
18
void initState() {
15
19
super.initState();
20
+
controller = AnimationController();
16
21
17
22
@override | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-21 | 17
22
@override
@@ -30,6 +35,12 @@
30
35
),
31
36
);
32
37
38
39
+
@override
40
+
void dispose() {
41
+
controller.dispose();
42
+
super.dispose();
43
+
}
33
44
34
45
class MyApp extends StatelessWidget {
This code is not yet valid because it passes no arguments
to AnimationController’s constructor. | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-22 | Remember the following observations whenever performing
this step with AnimationController:
You can instantiate AnimationController in several
different lifecycle methods,
but it is most common to use initState().
You should dispose of an AnimationController
when it is no longer needed—this reduces
the likelihood of memory leaks.
Always dispose of AnimationController
within the dispose() lifecycle method.
3. Pass AnimationController parameters
Pass arguments for vsync, duration, lowerBound,
and upperBound to the AnimationController constructor:
{explicit3 → explicit4}/lib/main.dart
@@ -1,5 +1,3 @@
// ignore_for_file: missing_required_argument
3
1
import 'dart:async';
4
2
import 'package:flutter/material.dart'; | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-23 | 4
2
import 'package:flutter/material.dart';
@@ -18,7 +16,12 @@
18
16
@override
19
17
void initState() {
20
18
super.initState();
21
controller = AnimationController();
19
+
controller = AnimationController(
20
+
vsync: this, // the SingleTickerProviderStateMixin
21
+
duration: const Duration(seconds: 1),
22
+
lowerBound: 0,
23
+
upperBound: 100, | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-24 | +
upperBound: 100,
24
+
);
22
25
23
26
@override
The vsync parameter makes use of the
SingleTickerProviderStateMixin you added in step 1:
vsync:
Remember from step 1 that vsync is a required parameter
that takes a TickerProvider.
By passing this for the vsync parameter,
you are passing _BouncingBallDemoState
as the TickerProvider object to the AnimationController constructor.
_BouncingBallDemoState implements the TickerProvider interface
because step 1 adds the SingleTickerProviderStateMixin
with _BouncingBallDemoState.
The duration, upperBound, and lowerBound parameters
define the following parts of your animation:
duration: The duration of the animation is 1 second. | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-25 | duration: The duration of the animation is 1 second.
upperBound and lowerBound:
Since the bouncing ball animation moves the ball
by transitioning its top-margin value from 0 to 100,
this step passes 0 as the lowerBound and 100 as the upperBound.
4. Add listener(s)
{explicit4 → explicit5}/lib/main.dart
@@ -22,12 +22,16 @@
22
22
lowerBound: 0,
23
23
upperBound: 100,
24
24
);
25
26
+
controller.addListener(() {
27
+
setState(() {});
28 | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-26 | +
setState(() {});
28
+
});
25
29
26
30
@override
27
31
Widget build(BuildContext context) {
28
32
return Container(
29
margin: const EdgeInsets.only(top: 0),
33
+
margin: EdgeInsets.only(top: controller.value),
30
34
child: Container(
31
35
decoration: const BoxDecoration(
32
36
shape: BoxShape.circle,
5. Trigger the animation | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-27 | shape: BoxShape.circle,
5. Trigger the animation
To start the bouncing ball animation so that
it repeats indefinitely, call AnimationController.repeat():
{explicit5 → explicit6}/lib/main.dart
@@ -26,6 +26,8 @@
26
26
controller.addListener(() {
27
27
setState(() {});
28
28
});
29
30
+
controller.repeat(reverse: true);
29
31
30
32
@override
This step calls repeat() within initState() because
the bouncing ball animation can begin immediately
when this view is | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-28 | AnimationController provides several methods for “driving” an animation:
repeat()
forward()
reverse()
stop()
reset()
Run the following example to see this explicit animation in action!
AnimationController concepts
As the name suggests, the AnimationController controls the
animation.
The Animation object
Lifecycle of an animation (completed, dismissed)
An Animation has a status and a value.
The value depends on what the user wants,
and can be of any type, such as or .
The controller’s status has four possible
values: dismissed, forward, reverse, and completed.
AnimationController is the central class that you use
to create explicit animations; its capabilities
fall into four categories:
defining animations, generating animation values,
registering listeners, and play or sequence controls: | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-29 | AnimationController makes it easy to access
the current value of the animation—just
use the value property.
To “play” an animation,
you can use one of several methods that
initiate the sequence of changes to value.
For example, to “play” an animation
from its starting value to its ending value,
simply call forward().
Use .addListener() to register a callback invoked whenever
AnimationController changes its value property.
Most commonly, you register setState() with AnimationController.
This tells Flutter to rebuild the widget tree
whenever AnimationController’s value changes.
AnimationController needs a TickerProvider to
synchronize the animation’s behavior to the device’s display.
AnimationController interpolates frame values
PENDING: Image of values in AnimationController
In this example,
the AnimationController constructor takes the
optional parameters lowerBound, upperBound,
and duration:
Instantiate AnimationController:
controller | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-30 | Instantiate AnimationController:
controller
AnimationController
lowerBound:
upperBound:
100
duration:
const
Duration
seconds:
),
vsync:
this
// Don't worry about vsync for now.
);
When you instantiate AnimationController,
you define an animation in terms of its starting value
(lowerBound), its ending value (upperBound),
and the amount of time it takes to change
from one to the other (duration).
The default values for lowerBound and upperBound
are 0 and 1, respectively; duration doesn’t have a default value.
Animation concepts section uses an | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-31 | Animation concepts section uses an
AnimationController
abstracts away the work of interpolation,
allowing you to reason about and create an animation
in terms of its duration, and the starting and ending
values of the property that you are animating:
AnimationController doesn’t know anything about the UI
Access animation values with controller.value
AnimationController provides a value property.
You can access this property directly—there
is no getter method for value:
print
controller
value
);
Curves
Use CurvedAnimation
you can use presets, or create your own
Tweens
To use a Tween call animate() passing in the controller. (example)
AnimatedBuilder
AnimatedWidget
TODO:
Explain that setState listener boilerplate isn’t normal. | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
508c079ecf33-32 | Explain that setState listener boilerplate isn’t normal.
Add section that uses AnimatedBuilder/AnimatedWidget
Refactor all DartPad samples to use non-working defaults,
& offer solution
Update vanilla bouncing ball final example to use both
upward and downward motion
“Why TickerProvider?” in animationController concepts section
How to choose between AnimatedBuilder and AnimatedWidget.
Answer question: when to use a Tween,
if you can just use upper and lower bound args for
AnimationController?
when we need something other than a double?
Add margin-bottom to DartPads
Add diffs between each solution in the introduction section | https://docs.flutter.dev/codelabs/explicit-animations/index.html |
0593b336d361-0 | Implicit animations
What are implicit animations?
Example: Fade-in text effect
Fade-in (starter code)
Animate opacity with AnimatedOpacity widget
1. Pick a widget property to animate
2. Initialize a state variable for the animated property
3. Set the duration of the animation
4. Set up a trigger for the animation, and choose an end value
Fade-in (complete)
Putting it all together
Example: Shape-shifting effect
Shape-shifting (starter code)
Animate color, borderRadius, and margin with AnimatedContainer
1. Add an implicit animation
2. Set starting values for animated properties
3. Set up a trigger for the animation
4. Set duration
Shape-shifting (complete)
Using animation curves
Putting it all together
What’s next? | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-1 | What’s next?
Welcome to the implicit animations codelab, where you learn how to use Flutter
widgets that make it easy to create animations for a specific set of properties.
Note:
This codelab uses embedded DartPads to display examples and exercises.
If you see empty boxes instead of DartPads, check out
Troubleshooting DartPad.
To get the most out of this codelab, you should have basic knowledge about:
How to make a Flutter app.
How to use stateful widgets.
This codelab covers the following material:
Using AnimatedOpacity to create a fade-in effect.
Using AnimatedContainer to animate transitions in size, color, and margin.
Overview of implicit animations and techniques for using them.
Estimated time to complete this codelab: 15-30 minutes. | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-2 | Estimated time to complete this codelab: 15-30 minutes.
What are implicit animations?
With Flutter’s animation library,
you can add motion and create visual effects
for the widgets in your UI.
One widget set in the library manages animations for you.
These widgets are collectively referred to as implicit animations,
or implicitly animated widgets, deriving their name from the
ImplicitlyAnimatedWidget class that they implement.
With implicit animations,
you can animate a widget property by setting a target value;
whenever that target value changes,
the widget animates the property from the old value to the new one.
In this way, implicit animations trade control for convenience—they
manage animation effects so that you don’t have to.
Example: Fade-in text effect | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-3 | Example: Fade-in text effect
The following example shows how to add a fade-in effect to existing UI
using an implicitly animated widget called AnimatedOpacity.
The example begins with no animation code—it
consists of a Material App home screen containing:
A photograph of an owl.
One Show details button that does nothing when clicked.
Description text of the owl in the photograph.
Fade-in (starter code)
Click the Run button to run the example:
Animate opacity with AnimatedOpacity widget
This section contains a list of steps you can use to add an
implicit animation to the
fade-in starter code. After the steps, you can also run the
fade-in complete code with the changes already made.
The steps outline how to use the AnimatedOpacity
widget to add the following animation feature:
The owl’s description text remains hidden until the user clicks the
Show details button. | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-4 | The owl’s description text remains hidden until the user clicks the
Show details button.
When the user clicks the Show details button,
the owl’s description text fades in.
1. Pick a widget property to animate
To create a fade-in effect, you can animate the opacity property using the
AnimatedOpacity widget. Change the Column widget to an
AnimatedOpacity widget:
{opacity1 → opacity2}/lib/main.dart
@@ -2,6 +2,8 @@
2
2
// Use of this source code is governed by a BSD-style license
3
3
// that can be found in the LICENSE file.
+
// ignore_for_file: missing_required_argument
4
6
import 'package:flutter/material.dart';
5
7 | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-5 | import 'package:flutter/material.dart';
5
7
const owlUrl =
@@ -25,12 +27,14 @@
25
27
style: TextStyle(color: Colors.blueAccent),
26
28
),
27
29
onPressed: () => {}),
28
Column(
29
children: const [
30
Text('Type: Owl'),
31
Text('Age: 39'),
32
Text('Employment: None'),
33
],
30
+
AnimatedOpacity( | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-6 | 30
+
AnimatedOpacity(
31
+
child: Column(
32
+
children: const [
33
+
Text('Type: Owl'),
34
+
Text('Age: 39'),
35
+
Text('Employment: None'),
36
+
],
37
+
),
34
38
35
39
]);
36
40
You can reference the line numbers in the example code to help track
where to make these changes. | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-7 | 2. Initialize a state variable for the animated property
To hide the text before the user clicks Show details, set
the starting value for opacity to zero:
{opacity2 → opacity3}/lib/main.dart
@@ -2,8 +2,6 @@
2
2
// Use of this source code is governed by a BSD-style license
3
3
// that can be found in the LICENSE file.
// ignore_for_file: missing_required_argument
6
4
import 'package:flutter/material.dart';
7
5
const owlUrl =
@@ -17,6 +15,8 @@
17
15
18
16 | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-8 | 17
15
18
16
class _FadeInDemoState extends State<FadeInDemo> {
17
+
double opacity = 0.0;
18
19
19
@override
20
20
Widget build(BuildContext context) {
21
21
return Column(children: <Widget>[
@@ -28,6 +28,8 @@
28
28
),
29
29
onPressed: () => {}),
30
30
AnimatedOpacity(
31
+
duration: const Duration(seconds: 3), | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-9 | +
duration: const Duration(seconds: 3),
32
+
opacity: opacity,
31
33
child: Column(
32
34
children: const [
33
35
Text('Type: Owl'),
3. Set the duration of the animation
In addition to an opacity parameter, AnimatedOpacity requires a
duration to use for its animation. For this example,
you can start with 2 seconds:
{opacity3 → opacity4}/lib/main.dart
@@ -28,7 +28,7 @@
28
28
),
29
29
onPressed: () => {}),
30
30 | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-10 | onPressed: () => {}),
30
30
AnimatedOpacity(
31
duration: const Duration(seconds: 3),
31
+
duration: const Duration(seconds: 2),
32
32
opacity: opacity,
33
33
child: Column(
34
34
children: const [
4. Set up a trigger for the animation, and choose an end value
{opacity4 → opacity5}/lib/main.dart
@@ -22,11 +22,14 @@
22
22
return Column(children: <Widget>[
23
23
Image.network(owlUrl), | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-11 | 23
23
Image.network(owlUrl),
24
24
TextButton(
25
child: const Text(
26
'Show Details',
27
style: TextStyle(color: Colors.blueAccent),
28
),
29
onPressed: () => {}),
25
+
child: const Text(
26
+
'Show Details',
27
+
style: TextStyle(color: Colors.blueAccent),
28
+
),
29 | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-12 | +
),
29
+
onPressed: () => setState(() {
30
+
opacity = 1;
31
+
}),
32
+
),
30
33
AnimatedOpacity(
31
34
duration: const Duration(seconds: 2),
32
35
opacity: opacity,
Notice that you only need to set the start and end values of opacity.
The AnimatedOpacity widget manages everything in between.
Fade-in (complete)
Here’s the example with the completed changes you’ve made—run this
example and click the Show details button to trigger the animation.
Putting it all together | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-13 | Putting it all together
The Fade-in text effect example demonstrates the following features
of AnimatedOpacity:
AnimatedOpacity listens for state changes in its opacity property.
Whenever opacity changes, AnimatedOpacity automatically animates the
widget’s transition to the new value for opacity.
AnimatedOpacity requires a duration parameter to define the time it takes
to animate the transition between an old opacity value and a new one.
Note that Implicit animations can only animate properties of a parent
StatefulWidget, so this example begins with the FadeInDemo widget that
extends StatefulWidget.
Notice also that AnimatedOpacity animates a single property: opacity.
Some implicitly animated widgets can animate many properties, as the following
example illustrates.
Example: Shape-shifting effect
AnimatedContainer widget to
animate multiple properties (
Material App home screen that contains: | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-14 | Material App home screen that contains:
A Container with borderRadius, margin, and color properties that are
different each time you run the example.
A Change button that does nothing when clicked.
Shape-shifting (starter code)
Click the Run button to run the example:
Animate color, borderRadius, and margin with AnimatedContainer
This section contains a list of steps you can use to add an
implicit animation to the shape-shifting starter code.
After the steps, you can also run the
shape-shifting complete example with the changes already made.
shape-shifting starter code,
each property in the
Generate new values for color, borderRadius,
and margin whenever the user clicks the Change button.
Animate the transition to the new values for color,
borderRadius, and margin whenever they are set.
1. Add an implicit animation | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-15 | 1. Add an implicit animation
Change the Container widget to an AnimatedContainer widget:
{container1 → container2}/lib/main.dart
@@ -2,6 +2,8 @@
2
2
// Use of this source code is governed by a BSD-style license
3
3
// that can be found in the LICENSE file.
+
// ignore_for_file: missing_required_argument
4
6
import 'dart:math';
5
7
import 'package:flutter/material.dart';
@@ -47,7 +49,7 @@
47
49
SizedBox(
48
50
width: 128, | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-16 | 48
50
width: 128,
49
51
height: 128,
50
child: Container(
52
+
child: AnimatedContainer(
51
53
margin: EdgeInsets.all(margin),
52
54
decoration: BoxDecoration(
53
55
color: color,
You can reference the line numbers in the example code to help track where to
make these changes in shape-shifting starter code
2. Set starting values for animated properties
{container2 → container3}/lib/main.dart
@@ -40,6 +40,14 @@
40
40 | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-17 | 40
40
margin = randomMargin();
41
41
42
+
void change() {
43
+
setState(() {
44
+
color = randomColor();
45
+
borderRadius = randomBorderRadius();
46
+
margin = randomMargin();
47
+
});
48
+
}
49
42
50
@override
43
51
Widget build(BuildContext context) {
44
52
return Scaffold( | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-18 | 44
52
return Scaffold(
3. Set up a trigger for the animation
To set the animation to trigger whenever the user presses the Change button,
invoke the change() method in the onPressed() handler:
{container3 → container4}/lib/main.dart
@@ -67,7 +67,7 @@
67
67
),
68
68
ElevatedButton(
69
69
child: const Text('change'),
70
onPressed: () => {},
70
+
onPressed: () => change(),
71
71
),
72
72
], | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-19 | ),
72
72
],
73
73
),
4. Set duration
Finally, set the duration of the animation that powers the transition
between the old and new values:
{container4 → container5}/lib/main.dart
@@ -2,12 +2,12 @@
2
2
// Use of this source code is governed by a BSD-style license
3
3
// that can be found in the LICENSE file.
// ignore_for_file: missing_required_argument
6
4
import 'dart:math';
7
5
import 'package:flutter/material.dart';
+
const _duration = Duration(milliseconds: 400); | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-20 | +
const _duration = Duration(milliseconds: 400);
8
8
double randomBorderRadius() {
9
9
return Random().nextDouble() * 64;
10
10
@@ -63,6 +63,7 @@
63
63
color: color,
64
64
borderRadius: BorderRadius.circular(borderRadius),
65
65
),
66
+
duration: _duration,
66
67
),
67
68
),
68
69
ElevatedButton(
Shape-shifting (complete) | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-21 | ElevatedButton(
Shape-shifting (complete)
Here’s the example with the completed changes you’ve made—run the code
and click the Change button to trigger the animation. Notice that each time
you click the Change button, the shape animates to its new values
for margin, borderRadius, and color.
Using animation curves
The preceding examples show how implicit animations allow you to animate
changes in values for specific widget properties, and how the
duration parameter allows you to set the amount of time an
animation takes to complete. Implicit animations also allow you to
control changes to the rate of an animation within the duration.
The parameter you use to define this change in rate is curve.
linear animation curve by default.
Add a
shape-shifting complete
and watch how the animation changes when you pass the
easeInOutBack constant for
{container5 → container6}/lib/main.dart | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-22 | {container5 → container6}/lib/main.dart
@@ -64,6 +64,7 @@
64
64
borderRadius: BorderRadius.circular(borderRadius),
65
65
),
66
66
duration: _duration,
67
+
curve: Curves.easeInOutBack,
67
68
),
68
69
),
69
70
ElevatedButton(
The easeInOutBack constant is only one of many that you can
pass for the curve parameter. Explore the
list of curve constants to discover more ways
to use curve to modify the look and feel of your animations.
Putting it all together | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-23 | Putting it all together
shape-shifting complete example animates transitions between values for
shape-shifting complete example builds upon
fade-in complete by showing
additional capabilities of implicit animations:
Some implicit animations (for example,
AnimatedOpacity) only animate a single
property, while others (like AnimatedContainer)
can animate many properties.
Implicit animations automatically animate between the old and
new values of properties when they change using the provided
curve and duration.
If you do not specify a curve,
implicit animations default to a linear curve.
What’s next?
Congratulations, you’ve finished the codelab! If you’d like to learn more,
here are some suggestions for where to go next:
Try the animations tutorial.
Learn about hero animations and staggered animations.
Checkout the animation library. | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
0593b336d361-24 | Checkout the animation library.
Try another codelab. | https://docs.flutter.dev/codelabs/implicit-animations/index.html |
03e56c9b600e-0 | Codelabs & workshops
Good for beginners
Next steps
Designing a Flutter UI
Using Flutter with…
Monetizing Flutter
Flutter and Firebase
Flutter and TensorFlow
Flutter and other technologies
Testing
Writing platform-specific code
Other resources
The Flutter codelabs provide a guided,
hands-on coding experience. Some codelabs
run in DartPad—no downloads required!
Flutter workshops are similar to the codelabs,
but are instructor led and always use DartPad.
The provided workshop link takes you to the relevant YouTube video,
which tells you where to find the associated DartPad link.
You might want to check out the workshops
created by our Google Developer Experts (GDEs).
You can find them on the Flutter community blog.
Good for beginners | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-1 | Good for beginners
If you’re new to Flutter, we recommend starting with
one of the following codelabs:
Your first Flutter app
Create a simple app that automatically generates cool-sounding names,
such as “newstay”, “lightstream”, “mainbrake”, or “graypine”.
This app is responsive and runs on mobile, desktop, and web.
(This also replaces the previous “write your first Flutter app”
for mobile, part 1 and part 2 codelabs.)
Write your first Flutter app on the web
Implement a simple web app in DartPad (no downloads
required!) that displays a sign-in screen
containing three text fields. As the user fills out the
fields, a progress bar animates along the top of the
sign-in area. This codelab is written specifically for
the web, but if you have downloaded and configured
Android and iOS tooling, the completed app
works on Android and iOS devices, as well.
Next steps | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-2 | Next steps
Building scrolling experiences in Flutter (workshop)
Start with an app that performs simple, straightforward scrolling
and enhance it to create fancy and custom scrolling effects
by using slivers.
Dart null safety in Action (workshop)
An instructor-led workshop based on the Null safety codelab
on the dart.dev site.
How to manage application states using inherited widgets (workshop)
Learn how to manage the state of your app’s data by
using the InheritedWidget class, one of the
low-level state management classes provided
by Flutter.
Designing a Flutter UI
Learn about Material Design and basic Flutter concepts,
like layout and animations:
Basic Flutter layout concepts
Use DartPad in a browser (no downloads required!)
to learn the basics of creating a Flutter layout. | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-3 | How to debug layout issues with the Flutter Inspector
Not an official codelab, but step-by-step instructions on
how to debug common layout problems using the Flutter
Inspector and Layout Explorer.
Implicit animations
Use DartPad (no downloads required!) to learn how to use
implicit animations to add motion and create
visual effects for the widgets in your UI.
Building Beautiful Transitions with Material Motion for Flutter
Learn how to use the Material animations package to
add pre-built transitions to a Material app called Reply.
Take your Flutter app from boring to beautiful
Learn how to use some of the features in Material 3
to make your app more beautiful and more responsive. | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-4 | MDC-101 Flutter: Material Components (MDC) Basics
Learn the basics of using Material Components by building
a simple app with core components. The four MDC codelabs
guide you through building an e-commerce app called Shrine.
You’ll start by building a login page using several of MDC
Flutter’s components.
MDC-102 Flutter: Material Structure and Layout
Learn how to use Material for structure and layout in Flutter.
Continue building the e-commerce app, introduced in MDC-101,
by adding navigation, structure, and data.
MDC-103 Flutter: Material Theming with Color, Shape, Elevation, and Type
Discover how Material Components for Flutter make it
easy to differentiate your product, and express your
brand through design. Continue building your e-commerce
app by adding a home screen that displays products. | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-5 | MDC-104 Flutter: Material Advanced Components
Improve your design and learn to use our advanced
component backdrop menu. Finish your e-commerce app
by adding a backdrop with a menu that filters
products by the selected category.
Adaptive Apps in Flutter
Learn how to build a Flutter app that adapts to the
platform that it’s running on, be that Android, iOS,
the web, Windows, macOS, or Linux.
Using Flutter with…
Learn how to use Flutter with other technologies.
Monetizing Flutter
Adding AdMob Ads to a Flutter app
Learn how to add an AdMob banner, an interstitial ad,
and a rewarded ad to an app called Awesome Drawing Quiz,
a game that lets players guess the name of the drawing. | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-6 | Adding an AdMob banner and native inline ads to a Flutter app
Learn how to implement inline banner and native ads
to a travel booking app that lists possible
flight destinations.
Adding in-app purchases to your Flutter app
Extend a simple gaming app that uses the Dash mascot as
currency to offer three types of in-app purchases:
consumable, non-consumable, and subscription.
Flutter and Firebase
Add a user authentication flow to a Flutter app using FirebaseUI
Learn how to add Firebase authentication to a Flutter app
with only a few lines of code.
Get to know Firebase for Flutter (workshop)
An instructor-led version of our popular
“Get to know Firebase for Flutter” codelab
(listed below).
Get to know Firebase for Flutter
Build an event RSVP and guestbook chat app on both Android
and iOS using Flutter, authenticating users with Firebase
Authentication, and sync data using Cloud Firestore. | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-7 | Local development for your Flutter apps using the Firebase Emulator Suite
Learn how to use the Firebase Emulator Suite when
developing with Flutter. You will also learn to use
the Auth and Firestore emulators.
Flutter and TensorFlow
Create a custom text-classification model with TensorFlow Lite Model Maker
Create a Flutter app to classify texts with TensorFlow
Learn how to run a text-classification inference from a Flutter
app with TensorFlow Serving through REST and gRPC.
Train a comment-spam detection model with TensorFlow Lite Model Maker
Learn how to install the TensorFlow Lite Model Maker with Colab,
How to use a data loader, and how to build a model.
Flutter and other technologies
Adding Google Maps to a Flutter app
Display a Google map in an app, retrieve data from a
web service, and display the data as markers on the map. | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-8 | Adding WebView to your Flutter app
With the WebView Flutter plugin you can add a WebView
widget to your Android or iOS Flutter app.
Build voice bots for mobile with Dialogflow and Flutter (workshop)
An instructor-led version of the Dialogflow
and Flutter codelab (listed below).
Build voice bots for Android with Dialogflow and Flutter
Learn how to build a mobile FAQ bot that can answer most
common questions about the tool Dialogflow. End users
can interact with the text interface or stream a voice
interaction via the built-in microphone of a mobile device.
Building a game with Flutter and Flame NEW
Learn how to create a platform game (featuring
Dash or Sparky), using the Flame package.
Using FFI in a Flutter plugin NEW
Learn how to use Dart’s FFI (foreign function interface)
library, ffigen, allowing you to leverage
existing native libraries that provide a
C interface. | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-9 | Testing
Learn how to test your Flutter application.
How to test a Flutter app
Start with a simple app that manages state with the Provider package.
Unit test the provider package. Write widget tests for two of the
widgets. Use Flutter Driver to create an integration test.
Writing platform-specific code
Learn how to write code that’s targeted for specific platforms,
like iOS, Android, desktop, or the web.
Building a Cupertino app with Flutter
Build a version of the Shrine shopping app
(used in the Material Design codelabs) using the
Cupertino package to create an iOS style look and feel.
Create multiple tabs and navigate between them.
Use the provider package to manage state between screens.
How to write a Flutter plugin
Learn how to write a plugin by creating a music plugin
for iOS and Android that processes audio on the host platform.
Then make an example app that uses your plugin to make a music keyboard. | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-10 | Using a plugin with a Flutter web app
Finish an app that reports the number of stars on a GitHub repository.
use Dart DevTools to do some simple debugging, and
Host your app on Firebase and, finally, use a Flutter plugin to
launch the app and open the hosted privacy policy.
Write a Flutter desktop application
Build a Flutter desktop app (Windows, Linux, or macOS)
that accesses GitHub APIs to retrieve your repositories,
assigned issues, and pull requests. As part of this task,
create and use plugins to interact with native APIs and desktop applications,
and use code generation to build type-safe client libraries for GitHub’s APIs.
Other resources
For Dart-specific codelabs, see the
codelabs page on the Dart site.
We also recommend the following online class:
The Complete Flutter Development Bootcamp Using Dart | https://docs.flutter.dev/codelabs/index.html |
03e56c9b600e-11 | The Complete Flutter Development Bootcamp Using Dart
Note:
If you have trouble viewing any of the codelabs
on codelabs.developers.google.com, try
this mirror of the Flutter codelabs. | https://docs.flutter.dev/codelabs/index.html |
770dd48484f7-0 | Basic Flutter layout concepts
Row and Column classes
Axis size and alignment
mainAxisSize property
mainAxisAlignment property
crossAxisAlignment property
Flexible widget
Expanded widget
SizedBox widget
Spacer widget
Text widget
Icon widget
Image widget
Putting it all together
What’s next?
Welcome to the Flutter layout codelab,
where you learn how to build a Flutter UI without
downloading and installing Flutter or Dart!
Note:
This codelab uses embedded DartPads to display examples and exercises.
If you see empty boxes instead of DartPads, check out
Troubleshooting DartPad. | https://docs.flutter.dev/codelabs/layout-basics/index.html |