如何保持用户登录 Flutter Firebase 应用程序？

Question

I am creating a chat app that uses Firebase for the backend. Whenever I restart the app, it goes to the welcome screen where users have to login/register, every single time. If you log in, then close the app without logging out, it still goes back to the login screen. I have added a method in the main method to check:

void getCurrentUser() async {
FirebaseAuth.instance.onAuthStateChanged.listen((firebaseUser) {
  print(firebaseUser);
  _user = firebaseUser;
});
}

So, if _user is null, then go to welcome page, otherwise go straight into the chat screen of the app:

Widget build(BuildContext context) {
getCurrentUser();
return MaterialApp(
  initialRoute: _user == null ? '/' : '/chat',
  routes: {
    '/': (context) => WelcomeScreen(),
    '/login': (context) => LoginScreen(),
    '/registration': (context) => RegistrationScreen(),
    '/chat': (context) => ChatScreen(),
  },
);
}

Why doesn't it work? I have Googled this problem for a while and earlier I was using auth.currentUser(), which could have been the problem, but now I'm using a listener and it still doesn't work.

Answer 1

var user await FirebaseAuth.instance.currentUser();
if (user != null) {
    Navigator.of(context).pushNamed("routeName");
}

Wrap the above code in an async function that takes BuildContext and call in the build method before the return statement.