返回页面后恢复 AnimationController 状态答案

【问题标题】：Restore AnimationController State Upon returning to Page返回页面后恢复 AnimationController 状态
【发布时间】：2019-11-09 01:41:00
【问题描述】：

我正在尝试保留倒数计时器的状态（下面给出示例），以便当我导航到倒数计时器页面时，开始倒计时，比如说在 10，然后暂停它，比如说在 7，然后导航离开Timer 和返回，Timer 显示 7，暂停时间，与 10 的初始状态。

在此处未显示的单独代码中，我尝试使用 PageStorageBucket + PageStorage 来存储 AnimationController，并在 InitState 中恢复它，但这不起作用。

在离开/返回到其所在页面后恢复动画控制器状态的最佳方法是什么？

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, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            FlatButton(
              color: Colors.blue,
              child: Text("AnimatonController"),
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => Counter()),
                );
              },
            ),
          ],
        ),
      ),
    );
  }
}

class CounterText extends AnimatedWidget {
  CounterText({Key key, this.animation})
      : super(key: key, listenable: animation);
  Animation<int> animation;

  @override
  build(BuildContext context) {
    return new Text(
      animation.value.toString(),
      style: new TextStyle(fontSize: 200.0),
    );
  }
}

class Counter extends StatefulWidget {
  State createState() => new _CounterState();
}

class _CounterState extends State<Counter> with TickerProviderStateMixin {
  AnimationController _controller;

  static const int startCount = 10;

  @override
  void initState() {
    super.initState();
    _controller = new AnimationController(
      vsync: this,
      duration: new Duration(seconds: startCount),
    );
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      floatingActionButton: new FloatingActionButton(
          child: Icon(_controller.isAnimating ? Icons.pause : Icons.play_arrow),
          onPressed: () {
            setState(() {
              _controller.isAnimating
                  ? _controller.stop()
                  : _controller.forward();
            });
          }),
      body: new Container(
        child: new Center(
          child: new CounterText(
            animation: new StepTween(
              begin: startCount,
              end: 0,
            ).animate(_controller),
          ),
        ),
      ),
    );
  }
}

【问题讨论】：

标签： flutter flutter-animation

【解决方案1】：

保存控制器状态的一种方法是使用Provider。

创建一个类来存储您的控制器状态，例如，

class CounterStateModel {
  AnimationController _controller;
  int startCount = 10;
}

将您的应用程序包装在提供程序中

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Provider<CounterStateModel>(
      builder: (context) => CounterStateModel(),
      child: MaterialApp(
        title: 'Flutter Demo',

然后在您的 _CounterState 类中，使用此提供程序来保存/检索您的控制器

  @override
  Widget build(BuildContext context) {
    CounterStateModel _counterStateModel = Provider.of<CounterStateModel>(context);

  if (_counterStateModel._controller == null) {
    _counterStateModel._controller = new AnimationController(
    vsync: this,
    duration: new Duration(seconds: _counterStateModel.startCount),
  );
  _counterStateModel._controller = _controller;
  } else {
    _controller = _counterStateModel._controller;
  }

  return new Scaffold(

完整代码是here

【讨论】：