import 'package:flutter/scheduler.dart';
@override
void initState() {
  super.initState();
  SchedulerBinding.instance.addPostFrameCallback((_) => {});
}

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

// 初始化状态，只执行一次
 void initState() { }
 
 // 当widget依赖的对象发生变化时调用，例如全局的主题或语言
 void didChangeDependencies() { }
 
 // 当widget重新构建时调用，根据canUpdate方法判断
 void didUpdateWidget(covariant T oldWidget) { }
 
 // 构建UI
 void build() { }
 
 // 调试模式下，热重载执行，Release模式不会执行
 void reassemble() { }
  
 // 当widget被移除时调用
 void deactivate() { }
 
 // 当widget被永久移除时，可以做释放资源
 void dispose() { }

abstract class WidgetsBindingObserver {
  //页面pop
  Future<bool> didPopRoute() => Future<bool>.value(false);
  //页面push
  Future<bool> didPushRoute(String route) => Future<bool>.value(false);
  //系统窗口相关改变回调，如旋转
  void didChangeMetrics() { }
  //文本缩放系数变化
  void didChangeTextScaleFactor() { }
  //系统亮度变化
  void didChangePlatformBrightness() { }
  //本地化语言变化
  void didChangeLocales(List<Locale> locale) { }
  //App生命周期变化
  void didChangeAppLifecycleState(AppLifecycleState state) { }
  //内存警告回调
  void didHaveMemoryPressure() { }
  //Accessibility相关特性回调
  void didChangeAccessibilityFeatures() {}
}

import 'package:flutter/material.dart';
import 'package:lifecyle/screen_two.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);
  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> with WidgetsBindingObserver {
  int _counter = 0;

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

  //当Widget第一次插入到Widget树时会被调用。
  //对于每一个State对象，Flutter只会调用该回调一次
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance!.addObserver(this);
    print("one initState");
  }

  //初始化时，在initState之后立刻调用
  //当State的依赖关系发生变化时，会触发此接口被调用
  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    print("one didChangeDependencies");
  }

  //状态改变的时候会调用该方法,比如父类调用了setState
  @override
  void didUpdateWidget(MyHomePage oldWidget) {
    super.didUpdateWidget(oldWidget);
    print("one didUpdateWidget");
  }

  //监听App生命周期回调
  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);
    print('one $state');
  }

  @override
  void reassemble() {
    super.reassemble();
    print("one reassemble");
  }

  //当State对象从树中被移除时，会调用此回调
  @override
  void deactivate() {
    super.deactivate();
    print('one deactivate');
  }

  //当State对象从树中被永久移除时调用；通常在此回调中释放资源
  @override
  void dispose() {
    super.dispose();
    WidgetsBinding.instance!.removeObserver(this);
    print("one dispose");
  }

  @override
  Widget build(BuildContext context) {
    print("one build");
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
            ElevatedButton(
              onPressed: () {
                Navigator.of(context).push(
                  MaterialPageRoute<void>(
                    builder: (BuildContext context) => const ScreenTwo(),
                  ),
                );
              },
              child: Text('Screen two'),
            ),
            Text('Minimize and check console or goto screen two ')
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

import 'package:flutter/material.dart';

class ScreenTwo extends StatefulWidget {
  const ScreenTwo({Key? key}) : super(key: key);

  @override
  _ScreenTwoState createState() => _ScreenTwoState();
}

class _ScreenTwoState extends State<ScreenTwo> with WidgetsBindingObserver {
//当Widget第一次插入到Widget树时会被调用。
  //对于每一个State对象，Flutter只会调用该回调一次
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance!.addObserver(this);
    print("two initState");
  }

  //初始化时，在initState之后立刻调用
  //当State的依赖关系发生变化时，会触发此接口被调用
  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    print("two didChangeDependencies");
  }

  //状态改变的时候会调用该方法,比如父类调用了setState
  @override
  void didUpdateWidget(ScreenTwo oldWidget) {
    super.didUpdateWidget(oldWidget);
    print("two didUpdateWidget");
  }

  //监听App生命周期回调
  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);
    print('two $state');
  }

  @override
  void reassemble() {
    super.reassemble();
    print("two reassemble");
  }

  //当State对象从树中被移除时，会调用此回调
  @override
  void deactivate() {
    super.deactivate();
    print('two deactivate');
  }

  //当State对象从树中被永久移除时调用；通常在此回调中释放资源
  @override
  void dispose() {
    super.dispose();
    WidgetsBinding.instance!.removeObserver(this);
    print("two dispose");
  }

  @override
  Widget build(BuildContext context) {
    print("two build");
    return Scaffold(
      appBar: AppBar(),
      body: Center(
        child: Text('Minimize and check console'),
      ),
    );
  }
}