Clash Royale CLAN TAG#URR8PPP

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

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.

createUserWithEmailAndPassword()

8 Answers
8

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.

createUserWithEmailAndPassword ()

auth/email-already-in-use

Alternatively, you can detect that an email address is already used by calling fetchSignInMethodsForEmail() (previous called fetchProvidersForEmail()).

fetchSignInMethodsForEmail()

fetchProvidersForEmail()

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());


);


First of all, you need to make sure you have that restriction enabled in Firebase console (Account and email address settings). Take a look at @Srinivasan's answer.

Then, do this in your java code:

firebaseAuthenticator.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>()
@Override
public void onComplete(@NonNull Task<AuthResult> task)
if (!task.isSuccessful())

if (task.getException() instanceof FirebaseAuthUserCollisionException)
Toast.makeText(SignUpActivity.this, "User with this email already exist.", Toast.LENGTH_SHORT).show();



else
sendVerificationEmail();
startActivity(new Intent(SignUpActivity.this, DetailsCaptureActivity.class));


// ...

);


This is where the trick happens:

if (task.getException() instanceof FirebaseAuthUserCollisionException) {
Toast.makeText(SignUpActivity.this,
"User with this email already exist.", Toast.LENGTH_SHORT).show();


Several exceptions can be thrown when registering a user with email and password, but the one we are interested in is the FirebaseAuthUserCollisionException. As the name implies, this exception is thrown if the email already exists. If the exception thrown is an instance of this class, let the user know.

FirebaseAuthUserCollisionException

As a practice of @Frank's answer here is the code of using fetchProvidersForEmail()

fetchProvidersForEmail()

private boolean checkAccountEmailExistInFirebase(String email)
FirebaseAuth mAuth = FirebaseAuth.getInstance();
final boolean b = new boolean[1];
mAuth.fetchProvidersForEmail(email).addOnCompleteListener(new OnCompleteListener<ProviderQueryResult>()
@Override
public void onComplete(@NonNull Task<ProviderQueryResult> task)
b[0] = !task.getResult().getProviders().isEmpty();

);
return b[0];



I was looking into this kind of condition where we can detect if user exists or not and perform registration and login. fetchProvidersForEmail is best option right now. I have found this tutorial. Hope it helps you too!

fetchProvidersForEmail

private ProgressDialog progressDialog;
progressDialog.setMessage("Registering, please Wait...");
progressDialog.show();

mAuth.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>()
@Override
public void onComplete(@NonNull Task<AuthResult> task)

//checking if success
if (task.isSuccessful())
//Registration was successfull:
Toast.makeText(RegistrationActivity.this, "Successfully registered!", Toast.LENGTH_LONG).show();

else
//Registration failed:
//task.getException().getMessage() makes the magic
Toast.makeText(RegistrationActivity.this, "Registration failed! " + "n" + task.getException().getMessage(), Toast.LENGTH_LONG).show();

progressDialog.dismiss();

);


Add below code to MainActivity.java file.When user attempt to register with the same email address a message "The email address is already used by another account" will pop up as a Toast

mAuth.createUserWithEmailAndPassword(email,password).addOnCompleteListener(new OnCompleteListener<AuthResult>()
@Override
public void onComplete(@NonNull Task<AuthResult> task)

if(!task.isSuccessful())

Toast.makeText(MainActivity.this, task.getException().getMessage(), Toast.LENGTH_SHORT).show();


if(task.isSuccessful())
Toast.makeText(MainActivity.this, "Sign up successfull", Toast.LENGTH_SHORT).show();



);


You do not have to do anything because the backend of Firebase will do the job.

Unless you are referring to reauthenticating of the app.
Take a scenario for an example, w

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