AnimatedSwitcher 组件过渡动画

AnimatedSwitcher 组件过渡动画

/// Flutter code sample for AnimatedSwitcher

// This sample shows a counter that animates the scale of a text widget
// whenever the value changes.

import 'package:flutter/material.dart';

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

/// This is the main application widget.
class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: _title,
      home: MyStatefulWidget(),
    );
  }
}

/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
  const MyStatefulWidget({Key? key}) : super(key: key);

  @override
  State<MyStatefulWidget> createState() => _MyStatefulWidgetState();
}

/// This is the private State class that goes with MyStatefulWidget.
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  int _count = 0;

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          AnimatedSwitcher(
            duration: const Duration(milliseconds: 500),
            transitionBuilder: (Widget child, Animation<double> animation) {
              return ScaleTransition(child: child, scale: animation);
            },
            child: Text(
              '$_count',
              // This key causes the AnimatedSwitcher to interpret this as a "new"
              // child each time the count changes, so that it will begin its animation
              // when the count changes.
              key: ValueKey<int>(_count),
              style: Theme.of(context).textTheme.headline4,
            ),
          ),
          ElevatedButton(
            child: const Text('Increment'),
            onPressed: () {
              setState(() {
                _count += 1;
              });
            },
          ),
        ],
      ),
    );
  }
}

 第二个用了SlideTransition。

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

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

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: buildChild(),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }

  buildChild() {
    return AnimatedSwitcher(
      duration: Duration(seconds: 1),
      transitionBuilder: (Widget child, Animation<double> animation) {
        Tween<Offset> tween = Tween(
          begin: Offset(0, 0),
          end: Offset(1, 1),
        );
        return SlideTransition(
          position: tween.animate(animation),
          child: child,
        );
      },
      child: Text(
        
        "$_counter",
        key: ValueKey("$_counter"),
        style: TextStyle(
          color: Colors.red,
          fontSize: 48,
          fontWeight: FontWeight.w600,
        ),
      ),
    );
  }
}