在扩展类型和普通类型之间颤动动画 FAB

Question

我想实现一个浮动操作按钮，它在扩展尺寸和正常尺寸之间进行动画处理，如在 Android Messenger 应用程序中所见：https://blog.usejournal.com/expand-collapse-fab-on-scrolling-like-googles-message-app-484df2d9d246

我怎样才能做到这一点？我目前正在研究使用 AnimatedSwitcher、FloatingActionButton.extended 和 FloatingActionButton 小部件。

Answer 1

This is my implementation using AnimatedSwitcher.

 import 'package:flutter/material.dart';

    void main() => runApp(MyApp());

    class MyApp extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          title: 'Flutter Demo',
          debugShowCheckedModeBanner: false,
          theme: ThemeData(
            primarySwatch: Colors.blue,
          ),
          home: MyHomePage(),
        );
      }
    }

    class MyHomePage extends StatefulWidget {
      @override
      _MyHomePageState createState() => _MyHomePageState();
    }

    class _MyHomePageState extends State<MyHomePage> {
      bool isIcon = false;

      Widget _myWidget = FloatingActionButton(
        key: UniqueKey(),
        onPressed: () {},
        child: Icon(Icons.message),
      );
      void _d() {
        setState(() {
          _myWidget = isIcon
              ? FloatingActionButton(
                  mini: true,
                  key: UniqueKey(),
                  onPressed: () {},
                  child: Icon(Icons.messsage),
                )
              : FloatingActionButton.extended(
                  key: UniqueKey(),
                  onPressed: () {},
                  icon: Icon(Icons.message),
                  label: Text("Start chat"),
                );
          isIcon = !isIcon;
        });
      }

      Widget build(context) {
        return Scaffold(
            floatingActionButton: isIcon
                ? AnimatedSwitcher(
                    duration: Duration(
                      milliseconds: 100,
                    ),
                    transitionBuilder: (Widget child, Animation<double> animation) {
                      return FadeTransition(
                        child: child,
                        opacity:
                            animation.drive(CurveTween(curve: Curves.elasticOut)),
                      );
                    },
                    child: _myWidget,
                  )
                : AnimatedSwitcher(
                    duration: Duration(
                      milliseconds: 100,
                    ),
                    transitionBuilder: (Widget child, Animation<double> animation) {
                      return FadeTransition(
                        child: child,
                        opacity:
                            animation.drive(CurveTween(curve: Curves.easeOutQuint)),
                      );
                    },
                    child: _myWidget,
                  ),
            appBar: AppBar(),
            body: FlatButton(
                onPressed: () {
                  _d();
                },
                child: Text('Press here to change FAB')));
      }
    }

This is my implementation by keeping the same Hero tag for the two FABs.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool isIcon = false;

  Widget _myWidget = FloatingActionButton(
    heroTag: 'd',
    key: UniqueKey(),
    onPressed: () {},
    child: Icon(Icons.message),
  );
  void _d() {
    setState(() {
      _myWidget = isIcon
          ? FloatingActionButton(
              heroTag: 'b',
              key: UniqueKey(),
              onPressed: () {},
              child: Icon(Icons.message),
            )
          : FloatingActionButton.extended(
              heroTag: 'b',
              key: UniqueKey(),
              onPressed: () {},
              icon: Icon(Icons.mesage),
              label: Text("Start chat"),
            );
      isIcon = !isIcon;
    });
  }

  Widget build(context) {
    return Scaffold(
        floatingActionButton: _myWidget,
        appBar: AppBar(),
        body: FlatButton(
            onPressed: () {
              _d();
            },
            child: Text('Press here to change FAB')));
  }
}

两者给出的结果不同，请根据需要尝试使用不同的动画曲线。改变 child 的大小，设置 Shape 边框，或将 mini: 设置为 true 以获得更好看的结果。

Answer 2

这是我做的

(your widget should be Stateful for this to work)

首先添加一个布尔值isExtended到你的Widget

bool isExtended = false;

然后添加一个新函数来切换你的isExtended值

的状态

void _switchActionBar() {
    setState(
      () {
        isExtended = !isExtended;
      },
    );
  }

最后像那样初始化 FloatingActionButon

FloatingActionButton.extended(
      isExtended: isExtended,
      onPressed: (){},
      label: isExtended
          ? Row(
              children: <Widget>[
                Padding(
                  padding: const EdgeInsets.only(right: 8.0),
                  child: Icon(Icons.add),
                ),
                Text("Start Editing"),
              ],
            )
          : Icon(Icons.add),
    );

就是这样，每当您调用 _switchActionBar() 时，您的浮动操作按钮将在扩展和正常之间进行动画处理。

Answer 3

只需在 FAB.extended 和普通 FAB 之间切换从普通FAB切换到扩展FAB时有动画，反之没有。

isextend
            ? FloatingActionButton.extended(
                onPressed: _switchActionBar,
                label: Text("Text"))
            : FloatingActionButton(
                onPressed: _switchActionBar,
                child: Icon(Icons.add),
              )

Answer 4

我能够使用带有 SizeTransition 和 FadeTransition 的 AnimatedSwitcher 让它工作。请看下面的代码。

floatingActionButton:
     FloatingActionButton.extended(
        onPressed: _onFabPress,
        label: AnimatedSwitcher(
          duration: Duration(seconds: 1),
          transitionBuilder: (Widget child, Animation<double> animation) =>
          FadeTransition(
            opacity: animation,
            child: SizeTransition(child:
            child,
              sizeFactor: animation,
              axis: Axis.horizontal,
            ),
          ) ,
          child: isExtended?
          Icon(Icons.arrow_forward):
          Row(
            children: [
              Padding(
                padding: const EdgeInsets.only(right: 4.0),
                child: Icon(Icons.add),
              ),
              Text("Add To Order")
            ],
          ),
        )
      )

只有图标的视图不是完全圆形的，但我相信可以通过调整填充来解决这个问题。

Answer 5

有一个包可以实现您期望的行为。这是https://pub.dev/packages/flutter_scrolling_fab_animated

在扩展类型和普通类型之间颤动动画 FAB

flutter animate FAB between extended and normal type

floating-action-button

flutter

flutter-animation