Flutter：如何设置 Stream 和提供程序

Question

I am making a Flutter app with Anonymous Sign In with Firebase (I'll add other sign in methods later). I want to create Stream and Provider so that if the user taps on Login button it takes the user to the Home() and if the user taps on Logout button inside Home() it takes it to Login() page.

I also want to do this for app restarts like when the user has logged in previously the user should be taken directly to Home() page instead of Login().

I've very basic knowledge of all this. Here, I'm following the FlutterFire docs. https://firebase.flutter.dev/docs/auth/usage/#authentication-state In this link they have talked about Stream and all but I'm not getting.

Here are my codes:

main.dart

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Wrapper(),
    );
  }
}

wrapper.dart

class Wrapper extends StatefulWidget {
  @override
  _WrapperState createState() => _WrapperState();
}

class _WrapperState extends State<Wrapper> {
  final FirebaseAuth _auth = FirebaseAuth.instance;
  @override
  Widget build(BuildContext context) {
    _auth.authStateChanges().listen((User user) {
      if (user == null) {
        print('the user is currently signed out');
        return Authenticate();
      } else {
        print('The User is currently signed In');
        return Home();
      }
    });
  }
}

AuthService

import 'package:firebase_auth/firebase_auth.dart';

class AuthenticationService {
  final FirebaseAuth _auth = FirebaseAuth.instance;

  //sign in anonympusly
  Future signinanon() async {
    try {
      UserCredential result = await _auth.signInAnonymously();
      User userdetails = result.user;
      return userdetails;
    } catch (e) {
      print(e.toString());
      return null;
    }
  }
}

Answer 1

You have many options here, but for simplicity's sake, you could use a StreamBuilder , and display different widgets, or pages if you please, depending on the authentication state.

authStateChanges is good here because, and I quote :

Firebase Auth enables you to subscribe in realtime to this state via a Stream. Once called, the stream provides an immediate event of the user's current authentication state , and then provides subsequent events whenever the authentication state changes.

Emphasis by me.