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的生命周期需要通過WidgetsBindingObserver的didChangeAppLifecycleState來獲取，在initState中添加監(jiān)聽WidgetsBinding.instance.addObserver(this);

resumed：可見并能響應(yīng)用戶的輸入
inactiv：處在并不活動(dòng)狀態(tài)，無法處理用戶響應(yīng)
paused：不可見并不能響應(yīng)用戶的輸入，但是在后臺(tái)繼續(xù)活動(dòng)中

class LifeCyclePageAState extends State<LifeCyclePageA> 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();
  }
  省略其他代碼...
}

推到后臺(tái)再回到前臺(tái)打印如下

image.png