How to delete a Firebase user from Android App?

Question

I'm trying to code a Delete User method in my Android App, but I have some issues each time I execute it. This method will be executed when a user pushes the Delete account button on an Activity. My apps works with FirebaseUI Auth.

Here is the method:

private void deleteAccount() {
    Log.d(TAG, "ingreso a deleteAccount");
    FirebaseAuth firebaseAuth = FirebaseAuth.getInstance();
    final FirebaseUser currentUser = firebaseAuth.getCurrentUser();

    currentUser.delete().addOnCompleteListener(new OnCompleteListener<Void>() {
        @Override
        public void onComplete(@NonNull Task<Void> task) {
            if (task.isSuccessful()) {
                Log.d(TAG,"OK! Works fine!");
                startActivity(new Intent(Main3WelcomeActivity.this, Main3Activity.class));
                finish();
            } 
        }
    }).addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            Log.e(TAG,"Ocurrio un error durante la eliminación del usuario", e);
        }
    });
}

1) When I execute that function a Smart Lock message appears on the screen and the user is signed in again. Here is a screenshot of this message.

2) On other occasions, when the user is logged in for a long time, the function throws an Exception like this:

06-30 00:01:26.672 11152-11152/com.devpicon.android.firebasesamples E/Main3WelcomeActivity: Ocurrio un error durante la eliminación del usuario
com.google.firebase.FirebaseException: An internal error has occured. [ CREDENTIAL_TOO_OLD_LOGIN_AGAIN ]
at com.google.android.gms.internal.zzacq.zzbN(Unknown Source)
at com.google.android.gms.internal.zzacn$zzg.zza(Unknown Source)
at com.google.android.gms.internal.zzacy.zzbO(Unknown Source)
at com.google.android.gms.internal.zzacy$zza.onFailure(Unknown Source)
at com.google.android.gms.internal.zzact$zza.onTransact(Unknown Source)
at android.os.Binder.execTransact(Binder.java:453)

I've read that I have to re-authenticate the user but I'm not sure how to do this when I'm working with Google Sign In.

Answer 1

As per the Firebase documentation can user delete() method to remove user from the Firebase

Before remove the user please reAuthenticate the user.

Sample code

     final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();

        // Get auth credentials from the user for re-authentication. The example below shows
        // email and password credentials but there are multiple possible providers,
        // such as GoogleAuthProvider or FacebookAuthProvider.
        AuthCredential credential = EmailAuthProvider
                .getCredential("user@example.com", "password1234");

        // Prompt the user to re-provide their sign-in credentials
        user.reauthenticate(credential)
                .addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
           user.delete()
            .addOnCompleteListener(new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    if (task.isSuccessful()) {
                        Log.d(TAG, "User account deleted.");
                    }
                }
            });

   }
});

For more details : https://firebase.google.com/docs/auth/android/manage-users#re-authenticate_a_user

If you want to user re Authentication with other singin provider only need to change the Provider for GoogleAuthProvider below is the sample code

GoogleAuthProvider.getCredential(googleIdToken,null);