Flutter Firebase Anonymous Authentification Sign-In Upon Opening

Question

I currently have an app which Sign's-In a User when a button is tapped by calling :

Future<void> anonymousSignIn(DocumentSnapshot<Object> document, context) async {
  await FirebaseAuth.instance.signInAnonymously();
  var user = await FirebaseAuth.instance.currentUser;
  var uid = user.uid;
  ScaffoldMessenger.of(context).showSnackBar(getSnackBar("Signed In"));
}

But I'd like the User to not have to press any button & instead be automatically Signed-In Anonymously when the App is Open - I'm not sure where to write that & how in my App

Also I ultimately will want to allow the user to also Sign-In with e-mail or Google so before Sign-In Anonymously upon Opening it will have to check if the user was not already Signed-In with those methods

🙏

Solution

You can do that by await FirebaseAuth.instance.signInAnonymously() it in your main() function before runApp(), so now you will have a user logged when the app starts.

I don't think your second part makes a sense, you will either automatically sign in the user anonymously or give him the options you mentioned which require the click to trigger Google oAuth flow or pass his credentials for the mail login.

Comments

[Sunshine]

thks I upvoted but I'm pretty sure I need to use Sign-In inside a Future thought ?

[esentis]

Well yes, you will add the async modifier at your main.

[esentis]

You will need to "persist" this information somehow and somewhere, maybe try using the pub.dev/packages/shared_preferences package to store the last sign in information.

[Sunshine]

ok thks - I wrote it inside Future main() async { } is it correct ?

[esentis]

You can remove the Future just async and void main() will do the trick.

[Sunshine]

i see - I thought Firebase_auth managed all of this & remembered that a user was Signed-In ?

[esentis]

Well it does, but if you sign your user anonymously, on the next login the user will still be anonymous. An anonymous user is still a valid user. If you sign in with Google, next time you open the app the user will still be signed on his Google account.

[Sunshine]

Oh i see so I have to save somehow in Shared Preferences that user had successfully logged into Google the last time & not logged out thank you 🙏

[Sunshine]

I think I need the Future to call await Firebase.initializeApp(); I'll keep just in case thank you : )