flutter - 实现authstatechanges后调用两次的类

Question

在尝试实现用于管理用户 session 的authStateChanges.listen()之后，该类被调用了两次，并导致两个内容相同的警报对话框，我不知道发生了什么，为什么要调用两次。
main()函数:

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(MaterialApp(home: EntryPoint(), debugShowCheckedModeBanner: false));
}

[编辑] EntryPoint类:

class EntryPoint extends StatefulWidget {
  _EntryPointState createState() => _EntryPointState();
}

class _EntryPointState extends State<EntryPoint> {
  // Set default `_initialized` and `_error` state to false
  bool _initialized = false;
  bool _error = false;
  FirebaseApp firebaseApp;

  // Define an async function to initialize FlutterFire
  void initializeFlutterFire() async {
    try {
      // Wait for Firebase to initialize and set `_initialized` state to true
      firebaseApp = await Firebase.initializeApp();
      setState(() {
        _initialized = true;
      });
    } catch (e) {
      // Set `_error` state to true if Firebase initialization fails
      setState(() {
        _error = true;
      });
    }
    FirebaseAuth.instance.authStateChanges().listen((User user) {
      if (user == null) {
        Navigator.push(context,
            MaterialPageRoute(builder: (BuildContext context) => LoginPage()));
      } else {
        Navigator.push(context,
            MaterialPageRoute(builder: (BuildContext context) => MyApp()));
            print('ok');
      }
    });
  }

  @override
  void initState() {
    this.initializeFlutterFire();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);

    return _getLandingPage();
  }
}

它在调试控制台中两次记录“确定”

Restarted application in 1,630ms.
D/ConnectivityManager(27325): unregisterNetworkCallback; CallingUid : 10392, CallingPid : 27325
D/ConnectivityManager(27325): unregisterNetworkCallback; CallingUid : 10392, CallingPid : 27325
W/example.confAp(27325): Accessing hidden method Ldalvik/system/CloseGuard;->close()V (light greylist, linking)
I/flutter (27325): ok
I/flutter (27325): ok
I/flutter (27325): IT IS CONNECTED BOYS
D/ConnectivityManager(27325): requestNetwork; CallingUid : 10392, CallingPid : 27325
W/DynamiteModule(27325): Local module descriptor class for providerinstaller not found.
I/flutter (27325): IT IS CONNECTED BOYS
I/DynamiteModule(27325): Considering local module providerinstaller:0 and remote module providerinstaller:0
W/ProviderInstaller(27325): Failed to load providerinstaller module: No acceptable module found. Local version is 0 and remote version is 0.
D/ConnectivityManager(27325): requestNetwork; CallingUid : 10392, CallingPid : 27325

编辑:添加了StreamBuilder

Widget _getLandingPage() {
  return StreamBuilder<User>(
    stream: FirebaseAuth.instance.authStateChanges(),
    builder: (BuildContext context, snapshot) {
      if (snapshot.hasData) {
        return MyApp();
      } else {
        return LoginPage();
      }
    },
  );
}

Answer 1

也许是在SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);方法中调用build的问题。尝试将其删除。
第二个问题似乎与initState中的调用方法有关。尝试使用StreamBuilder从Firebase监听Authentication changes。对StreamBuilder应用相同的逻辑。