Flutter:如何设置观察者整个应用程序

dependencies:
  flutter:
    sdk: flutter
  provider: ^6.0.0

import 'package:flutter/material.dart';

class AppState extends ChangeNotifier {
  // 定义应用程序的状态
  bool isDarkMode = false;

  // 定义修改状态的方法
  void toggleDarkMode() {
    isDarkMode = !isDarkMode;
    notifyListeners();
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'My App',
      theme: ThemeData(
        brightness: Provider.of<AppState>(context).isDarkMode
            ? Brightness.dark
            : Brightness.light,
      ),
      home: HomePage(),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Home'),
      ),
      body: Consumer<AppState>(
        builder: (context, appState, child) {
          return SwitchListTile(
            title: Text('Dark Mode'),
            value: appState.isDarkMode,
            onChanged: (value) {
              appState.toggleDarkMode();
            },
          );
        },
      ),
    );
  }
}