错误: flutter中不存在包androidx.lifecycle

import 'package:flutter/material.dart';

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);
    // 在这里处理应用程序生命周期事件
    switch (state) {
      case AppLifecycleState.resumed:
        // 应用程序从后台切换到前台
        break;
      case AppLifecycleState.inactive:
        // 应用程序进入非活动状态
        break;
      case AppLifecycleState.paused:
        // 应用程序进入后台
        break;
      case AppLifecycleState.detached:
        // 应用程序被挂起
        break;
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // 应用程序界面
    );
  }
}