Flutter: about monitoring on flutter applications

Write it at the front

Yes Flutter Record some places that need relevant monitoring

Content

WidgetsBindingObserver

Mix in WidgetsBindingObserver after , We can implement some monitoring .

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

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {

  @override
  void initState() {
    WidgetsBinding.instance.addObserver(this);
    super.initState();
  }

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: Builder(
          builder: (BuildContext context) {
            return Center(
              child: Column(
                children: [
                  TextButton(
                      onPressed: () {
                        Navigator.push(context,
                            MaterialPageRoute(builder: (context) {
                          return SecondPage();
                        }));
                      },
                      child: Text("press")),
                ],
              ),
            );
          },
        ),
      ),
    );
  }
}

App Front and rear monitoring

stay didChangeAppLifecycleState() in , We can monitor app In the running state of the front and rear platforms .

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    print(state.toString());
    super.didChangeAppLifecycleState(state);
  }

When the home Key let app When you step back from the front desk to the backstage , give the result as follows ：

flutter: AppLifecycleState.inactive
flutter: AppLifecycleState.paused

Then switch from the background to the foreground ：

flutter: AppLifecycleState.inactive
flutter: AppLifecycleState.resumed

AppLifecycleState

AppLifecycleState There are several States ：

• resumed
• inactive
• paused
• detached

resumed

Express app It is visible and can respond to user input

inactive

Express app Is inactive and cannot respond to user input

iOS

stay iOS On , If there is a phone call 、Touch ID Request , Or sliding out the control bar will make it in inactive state .

Android

stay Android On , If there is a phone call 、 the other one Activity Got the focus （ For example, split screen app）、 Picture in picture app、 A system pop-up window, etc , Will make it in inactive state .

paused

This state means that the application cannot be seen by the user at this time , Unable to respond to user input , And it runs in the background .

In this state ,Flutter Engine Not invoke PlatformDispatcher.onBeginFrame and PlatformDispatcher.onDrawFrame Callback .

detached

In this state ,app Still will be Flutter Engine Held by , But not by any host View hold . That is to say, at this time Engine There is no View Operation in case of .

But at present, there should be some defects in callback , You can further view AppLifeCycleState.detached is not called when app is closed quickly #57594