使用Main App时如何刷新Widget？

// Main App中刷新Widget的示例
class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  int _counter = 0;

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('My App'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text('Counter: $_counter'),
              RaisedButton(
                onPressed: () {
                  // 刷新Widget
                  setState(() {});
                },
                child: Text('Refresh Widget'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

// Main App中刷新Widget的示例（使用Provider）
class Counter with ChangeNotifier {
  int _count = 0;

  int get count => _count;

  void increment() {
    _count++;
    notifyListeners(); // 通知监听者（即Widget）进行刷新
  }
}

void main() {
  runApp(
    ChangeNotifierProvider(
      create: (context) => Counter(),
      child: MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('My App'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text('Counter: ${counter.count}'),
              RaisedButton(
                onPressed: () {
                  // 刷新Widget
                  counter.increment();
                },
                child: Text('Refresh Widget'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

// Main App中刷新Widget的示例（使用事件总线）
import 'package:event_bus/event_bus.dart';

EventBus eventBus = EventBus();

class RefreshEvent {
  // 自定义刷新事件
}

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('My App'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text('Widget A'),
              RaisedButton(
                onPressed: () {
                  // 发送刷新事件
                  eventBus.fire(RefreshEvent());
                },
                child: Text('Refresh Widget'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class WidgetB extends StatefulWidget {
  @override
  _WidgetBState createState() => _WidgetBState();
}

class _WidgetBState extends State<WidgetB> {
  bool _isRefreshed = false;

  @override
  void initState() {
    super.initState();
    // 订阅刷新事件
    eventBus.on<RefreshEvent>().listen((event) {
      setState(() {
        _isRefreshed = true;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Text('Widget B: $_isRefreshed');
  }
}