Question 76256 in Flutter Question posted in
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login in anonymous mode if no info in shared preferences – Flutter

I’m trying to sign in the user in anonymous mode automatically using firebase anonymous authentication, only if the user is not already registered and signed. Using shared preferences, I check during the appearing of the splash screen if the user is already signed in as follows:

getValidationData().whenComplete(() async {
  await Future.delayed(Duration(milliseconds: 4000));
  // ignore: use_build_context_synchronously
  Navigator.pushReplacement(
      context,
      MaterialPageRoute(
        builder: (context) =>
            finalEmail == null ? LoginScreen() : HomeScreen(),
      ));
});

in the getValidationData() function, this is the code:

  Future getValidationData() async {
    final SharedPreferences sharedPreferences =
        await SharedPreferences.getInstance();
    var obtainedEmail = sharedPreferences.getString('email');
    setState(() {
      finalEmail = obtainedEmail;
    });
  }

As you may have noticed if no email found in shared preferences the user will be redirected to the login screen. What I want is to redirect the user to the home page as a guest (Anonymous) using the firebase service which is implemented in my code as follows:

class authService {
  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;

  User? get currentUser => _firebaseAuth.currentUser;

  Future<User> getOrCreateUser() async {
    if (currentUser == null) {
      await _firebaseAuth.signInAnonymously();
    }
    return currentUser!;
  }
}

My problem is that I am not sure where to create the anonymous authentication if no shared preferences found, I’ll appreciate any help.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    I have solved my problem by doing a little tweak in the code, so instead of checking if the user already logged in like this:

    getValidationData().whenComplete(() async {
  await Future.delayed(Duration(milliseconds: 4000));
  // ignore: use_build_context_synchronously
  Navigator.pushReplacement(
      context,
      MaterialPageRoute(
        builder: (context) =>
            finalEmail == null ? LoginScreen() : HomeScreen(),
      ));
});

    we can log the user anonymously if no shared preferences information found like this:

     getValidationData().whenComplete(() async {
              await Future.delayed(Duration(milliseconds: 4000));
              // ignore: use_build_context_synchronously
              if (finalEmail == null) {
                // ignore: use_build_context_synchronously
                await authService().getOrCreateUser();
                Navigator.pop(context);
                Navigator.push(
                    context,
                    MaterialPageRoute(
                        builder: (context) => const HomeScreen()));
              } else {
                Navigator.push(
                    context,
                    MaterialPageRoute(
                        builder: (context) => const HomeScreen()));
              }
            });

    Hopefully it will help anyone trying to achieve the same approach.


  2. 0

    Assumptions

    • There are 3 types of use cases:

      1. User is already signed in and registered
      2. User is signed out but registered
      3. User is signed out and not registered

    • Using shared_preferences or any kind of local storage solution to differentiate between 2 and 3 is a bad idea. Local storage can be wiped out. Hence I am assuming we cannot differentiate between 2 and 3.

    • In case of 1, user is redirected to homepage

    • In case of 2 and 3, you can redirect the user to login screen and give them an option to enter without signing in.

    What to do:

    1. If the user is signed in, you’ll get a User result from _firebaseAuth.currentUser

    2. If you get null from _firebaseAuth.currentUser then, signIn user anonymously, you don’t need sharedPreferences.

    Where to do it:

    Please call these functions in splashscreen:

    Future<bool> isUserLoggedIn() async{
  return FirebaseAuth.instance.currentUser != null;
}

Future<void> handleUserRedirection() async {
  final bool userLogin = await isUserLoggedIn();
  Navigator.pushReplacement(
      context,
      MaterialPageRoute(
        builder: (context) =>
            !userLogin? LoginScreen() : HomeScreen(),
      ));
}
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