Implicit Flutter Animations

Oct 4 2022 Dart 2.17, Flutter 3.0, Visual Studio Code 1.7

Part 2: Implicit Animations in Action

5. Animate a Social Share Button

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Previous episode: 4. Create Custom Implicit Animations Next episode: 6. Create a Custom PageView Animation

The student materials have been reviewed and are updated as of August 2022.

The updated material uses null safety and also deploys the use coding practises encouraged by the Flutter as per the Flutter lint rules and a few addons of practises that are considered good here at raywenderlich (see analysis_options.yaml in the material for more info).

Also, since the Flutter 2, it is now necessary to explicitly specify the type that an expression or method can return. If dart is unable to infer the actual type but assumes it return generic type like Object? then it is necessary to casting to actual type as well.

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In this section, we are going to apply our knowledge of implicit animations to add animations to the RW-Eats app. We would be covering more implicitly animated widgets.

...
Container(
    //width: 48,
    width: 240,
..
Opacity(
    //opacity: 0,
    opacity: 1,
...
bool isOpen = false;

void _toggleShare() {
    setState(() {
      isOpen = !isOpen;
    });
}
...
AnimatedContainer(
    duration: const Duration(milliseconds: 350),
    curve: Curves.fastOutSlowIn,
    width: isOpen ? 240 : 48,
...
Container(
    child: IconButton(
        icon: const Icon(Icons.share),
        onPressed: () => _toggleShare(),
...
AnimatedOpacity(
    duration: const Duration(milliseconds: 450),
    opacity: isOpen ? 1 : 0,
child: AnimatedCrossFade(
    duration: const Duration(milliseconds: 450),
    firstChild: IconButton(
      icon: const Icon(Icons.share),
      onPressed: () => _toggleShare(),
    ),
    secondChild: IconButton(
      icon: const Icon(Icons.close),
      onPressed: () => _toggleShare(),
    ),
    crossFadeState: !isOpen
        ? CrossFadeState.showFirst
        : CrossFadeState.showSecond,
),