【自学Flutter】 交错动画的使用

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}
 
class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}
 
class _HomePageState extends State<HomePage> with TickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;
 
  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 3),
      vsync: this,
    )..repeat(reverse: true);
 
    _animation = Tween<double>(begin: 0, end: 300).animate(_controller)
      ..addListener(() => setState(() {}));
  }
 
  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('交错动画示例')),
      body: Center(
        child: Container(
          margin: EdgeInsets.symmetric(vertical: 10),
          height: _animation.value,
          width: _animation.value,
          child: FlutterLogo(),
        ),
      ),
    );
  }
}

这段代码创建了一个简单的交错动画示例，其中一个Flutter徽标会在一个3秒钟的动画周期内来回交错放大缩小。代码使用了AnimationController和Tween来定义动画曲线，并通过addListener在动画每一帧更新时重绘UI。