Firebase keeps user loged in after logout in flutter

Question

my goal in flutter is to ensure that the app closes after the user has logged out. However, I have a small problem here.

in my application the user is asked if he wants to log out if he presses yes the following code is executed.

         onPressed: () async {
            var auth = FirebaseAuth.instance;
            await auth.signOut();

            FirebaseAuth.instance.authStateChanges().listen((User? user) {
              if (user == null) {
                print('Exiting app');
                exit(8); //this closes the app
              }
            });
          },

However, this causes me to get a message in the console that the user is logged out and then the app closes as expected. However, if I then open the app, the user is logged in again. How can I prevent this?

my Console output (after pressing the Button) is as follows:

D/FirebaseAuth( 2809): Notifying id token listeners about a sign-out event.
D/FirebaseAuth( 2809): Notifying auth state listeners about a sign-out event.
I/flutter ( 2809): Exiting app

Answer 1

The issue you're facing occurs because exit() forcibly closes the app without properly saving the user's logged-out state. This could prevent Firebase from fully processing the logout event.

Instead, use SystemNavigator.pop(), and also make sure that you clear any stored session if you have used it:

onPressed: () async {
  var auth = FirebaseAuth.instance;
  await auth.signOut();  // Signs out the user

  // Clear any local storage or session data
  // For example, using shared preferences:
  SharedPreferences prefs = await SharedPreferences.getInstance();
  await prefs.clear();  // Clear stored user session

  FirebaseAuth.instance.authStateChanges().listen((User? user) {
    if (user == null) {
      print('User logged out successfully');
      SystemNavigator.pop(); // Close the app gracefully
    }
  });
},