import 'package:flutter/material.dart';

class LifecycleAwareWidget extends StatefulWidget {
  @override
  _LifecycleAwareWidgetState createState() => _LifecycleAwareWidgetState();
}

class _LifecycleAwareWidgetState extends State<LifecycleAwareWidget>
    with WidgetsBindingObserver { // 1. 混入 WidgetsBindingObserver

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this); // 2. 注册观察者
    print('Widget initState - Observer added');
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this); // 4. 移除观察者，防止内存泄漏
    print('Widget dispose - Observer removed');
    super.dispose();
  }

  // 3. 实现回调方法
  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    print('AppLifecycleState changed: $state');
    switch (state) {
      case AppLifecycleState.resumed:
        // 应用回到前台
        print('App is back in foreground!');
        // 示例：重新加载数据，恢复动画，重新连接Socket等
        break;
      case AppLifecycleState.inactive:
        // 应用处于不活跃状态（如iOS来电、多任务切换器）
        print('App is inactive.');
        // 示例：暂停非关键的动画
        break;
      case AppLifecycleState.paused:
        // 应用进入后台
        print('App is in background.');
        // 示例：保存数据，暂停媒体播放，断开Socket，停止相机等
        break;
      case AppLifecycleState.detached:
        // 应用被分离（Android，Flutter引擎视图被移除）
        print('App is detached.');
        // 示例：执行最后的清理
        break;
      case AppLifecycleState.hidden:
        // 应用被隐藏 (Web 或特定场景，不常用)
        print('App is hidden.');
        break;
    }
  }

  @override
  void didChangeMetrics() {
    print('Metrics changed (e.g., screen size, orientation)');
    // 示例：响应屏幕旋转
  }

  @override
  void didChangePlatformBrightness() {
    print('Platform brightness changed (dark/light mode)');
    // 示例：更新自定义UI的主题
  }

  @override
  void didChangeLocales() {
    print('Locales changed (language settings)');
    // 示例：重新加载国际化资源
  }

  @override
  void didHaveMemoryPressure() {
    print('Received memory pressure warning!');
    // 示例：清理缓存
  }

  // 其他回调方法...

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('WidgetsBindingObserver Demo'),
      ),
      body: Center(
        child: Text('Check console for lifecycle and system events!'),
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: LifecycleAwareWidget(),
  ));
}

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


void main() {
  runApp(const AppLifecycleListenerExample());
}

class AppLifecycleListenerExample extends StatelessWidget {
  const AppLifecycleListenerExample({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(home: Scaffold(body: AppLifecycleDisplay()));
  }
}

class AppLifecycleDisplay extends StatefulWidget {
  const AppLifecycleDisplay({super.key});

  @override
  State<AppLifecycleDisplay> createState() => _AppLifecycleDisplayState();
}

class _AppLifecycleDisplayState extends State<AppLifecycleDisplay> {
  late final AppLifecycleListener _listener;
  final ScrollController _scrollController = ScrollController();
  final List<String> _states = <String>[];
  late AppLifecycleState? _state;

  @override
  void initState() {
    super.initState();
    _state = SchedulerBinding.instance.lifecycleState;
    _listener = AppLifecycleListener(
      onShow: () => _handleTransition('show'),
      onResume: () => _handleTransition('resume'),
      onHide: () => _handleTransition('hide'),
      onInactive: () => _handleTransition('inactive'),
      onPause: () => _handleTransition('pause'),
      onDetach: () => _handleTransition('detach'),
      onRestart: () => _handleTransition('restart'),
      onStateChange: _handleStateChange,
    );
    if (_state != null) {
      _states.add(_state!.name);
    }
  }

  @override
  void dispose() {
    _listener.dispose();
    super.dispose();
  }

  void _handleTransition(String name) {
    setState(() {
      _states.add(name);
    });
    _scrollController.animateTo(
      _scrollController.position.maxScrollExtent,
      duration: const Duration(milliseconds: 200),
      curve: Curves.easeOut,
    );
  }

  void _handleStateChange(AppLifecycleState state) {
    setState(() {
      _state = state;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: SizedBox(
        width: 300,
        child: SingleChildScrollView(
          controller: _scrollController,
          child: Column(
            children: <Widget>[
              Text('Current State: ${_state ?? 'Not initialized yet'}'),
              const SizedBox(height: 30),
              Text('State History:\n  ${_states.join('\n  ')}'),
            ],
          ),
        ),
      ),
    );
  }
}