Flutter 之 Widget&App生命周期

Widget的生命周期

• StatelessWidget

  StatelessElement createElement()
  Widget build(BuildContext context)
  

• StatefulWidget

  
  
  image.png

  void initState()
  void didChangeDependencies()
  Widget build(BuildContext context)
  void reassemble()
  void didUpdateWidget(LifeCyclePage oldWidget)
  void deactivate()
  void dispose()
  

App的生命周期

App的生命周期需要通过WidgetsBindingObserver的didChangeAppLifecycleState来获取，在initState中添加监听WidgetsBinding.instance.addObserver(this);

resumed：可见并能响应用户的输入
inactiv：处在并不活动状态，无法处理用户响应
paused：不可见并不能响应用户的输入，但是在后台继续活动中

class LifeCyclePageAState extends State with WidgetsBindingObserver {
  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    switch (state) {
      case AppLifecycleState.resumed:
        print("app resumed");
        break;
      case AppLifecycleState.inactive:
        print("app inactive");
        break;
      case AppLifecycleState.paused:
        print("app paused");
        break;
      case AppLifecycleState.detached:
        print("app detached");
        break;
    }

    super.didChangeAppLifecycleState(state);
  }

  @override
  void initState() {
    print("initState A");
    WidgetsBinding.instance.addObserver(this);
    super.initState();
  }
  省略其他代码...
}

推到后台再回到前台打印如下

image.png