这是一个最小的工作解决方案。关键点：
- 介绍
TimerService
隔离计时器功能的类 TimerService
实现ChangeNotifier
，您可以订阅以接收更改。- 一个
InheritedWidget
用于提供服务给您的应用程序的所有部件。这个继承的小部件包装了您的应用小部件。 AnimatedBuilder
用于接收来自的更改ChangeNotifier
。订阅是自动处理的（无手动addListener
/removeListener
）。
import 'dart:async';import 'package:flutter/material.dart';void main() { final timerService = TimerService(); runApp( TimerServiceProvider( // provide timer service to all widgets of your app service: timerService, child: MyApp(), ), );}class TimerService extends ChangeNotifier { Stopwatch _watch; Timer _timer; Duration get currentDuration => _currentDuration; Duration _currentDuration = Duration.zero; bool get isRunning => _timer != null; TimerService() { _watch = Stopwatch(); } void _onTick(Timer timer) { _currentDuration = _watch.elapsed; // notify all listening widgets notifyListeners(); } void start() { if (_timer != null) return; _timer = Timer.periodic(Duration(seconds: 1), _onTick); _watch.start(); notifyListeners(); } void stop() { _timer?.cancel(); _timer = null; _watch.stop(); _currentDuration = _watch.elapsed; notifyListeners(); } void reset() { stop(); _watch.reset(); _currentDuration = Duration.zero; notifyListeners(); } static TimerService of(BuildContext context) { var provider = context.inheritFromWidgetOfExactType(TimerServiceProvider) as TimerServiceProvider; return provider.service; }}class TimerServiceProvider extends InheritedWidget { const TimerServiceProvider({Key key, this.service, Widget child}) : super(key: key, child: child); final TimerService service; @override bool updateShouldNotify(TimerServiceProvider old) => service != old.service;}class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Service Demo', home: MyHomePage(), ); }}class MyHomePage extends StatefulWidget { @override _MyHomePageState createState() => _MyHomePageState();}class _MyHomePageState extends State<MyHomePage> { @override Widget build(BuildContext context) { var timerService = TimerService.of(context); return Scaffold( appBar: AppBar(), body: Center( child: AnimatedBuilder( animation: timerService, // listen to ChangeNotifier builder: (context, child) { // this part is rebuilt whenever notifyListeners() is called return Column( mainAxisAlignment: MainAxisAlignment.center, children: <Widget>[ Text('Elapsed: ${timerService.currentDuration}'), RaisedButton( onPressed: !timerService.isRunning ? timerService.start : timerService.stop, child: Text(!timerService.isRunning ? 'Start' : 'Stop'), ), RaisedButton( onPressed: timerService.reset, child: Text('Reset'), ) ], ); }, ), ), ); }}
