flutter - flutter root widget 应该始终是 StatelessWidget 吗？

Question

当我在 flutter 中阅读文档时，我有一个问题，flutter root widget 应该始终是 StatelessWidget 吗？

 class MyApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
       title: 'Flutter Code Sample for Navigator',
       // MaterialApp contains our top-level Navigator
       initialRoute: '/',
       routes: {
         '/': (BuildContext context) => HomePage(),
         '/signup': (BuildContext context) => SignUpPage(),
       },
     );
   }
 }

1. 因为我觉得有些时候需要调用init函数，可能不想把那个代码写在HomePage里。例如:检查token是否过期，决定去HomePage还是LoginPage。
2. 那么最好的选择是:我是否应该将根 Widget 更改为 StatefulWidget，并将上面的逻辑包含在其 initState 函数中？

Answer 1

让根widget成为StatefulWidget在监听AppLifecycleState时很有用
例如恢复 WebSocket 连接之类的恢复工作

代码片段

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

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {

  AppLifecycleState _lastLifecycleState;


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

  }

  initPlatformState() async {
    Screen.keepOn(true);   
  }

  Future<void> resumeCallBack() {
    if (sl<WebSocketService>().webSocketState == 'lost') {
      sl<WebSocketService>().initWebSocket();
    }

    if (mounted) {
      setState(() {});
    }
    print("resumeCallBack");
  }

  Future<void> suspendingCallBack() {
    if (mounted) {
      setState(() {});
    }
    print("suspendingCallBack");
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) async {
    super.didChangeAppLifecycleState(state);
    print("AppLifecycleState Current state = $state");
    setState(() {
      _lastLifecycleState = state;
    });

    switch (state) {
      case AppLifecycleState.inactive:
      case AppLifecycleState.paused:
      case AppLifecycleState.detached:
      /*case AppLifecycleState.suspending:
        await suspendingCallBack();
        break;*/
      case AppLifecycleState.resumed:
        await resumeCallBack();
        break;
    }
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Template',
      debugShowCheckedModeBanner: false,
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      initialRoute: '/',
      routes: {
        '/': (context) => LoginPage(),