Firebase Auth - with Email and Password - Check user already registered

Question

I want to check when a user attempts to signup with createUserWithEmailAndPassword() in Firebase user Authentication method, this user is already registered with my app.

Answer 1

To detect whether a user with that email address already exists, you can detect when the call to createUserWithEmailAndPassword () fails with auth/email-already-in-use. I see that @Srinivasan just posted an answer for this.

Alternatively, you can detect that an email address is already used by calling fetchSignInMethodsForEmail(). The usual flow for this is that you first ask the user to enter their email address, then call fetchSignInMethodsForEmail, and then move them to a screen that either asks for the rest of their registration details (if they're new), or show them the provider(s) with which they're signed up already.

Answer 2

When the user trying to create an user with same email address, the task response will be "Response: The email address is already in use by another account."

mFirebaseAuth.createUserWithEmailAndPassword(email,password)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {                           
                        if(task.isSuccessful()){
                           //User registered successfully
                        }else{
                            Log.i("Response","Failed to create user:"+task.getException().getMessage());
                        }
                    }
                });