Whatsapp-Like Phone Number Authentication with Firebase

Firebase Authentication with phone number means a user can sign-in by sending an SMS message to the user’s phone. The user signs in using a one-time code contained in the SMS message.

This is likened to Whatsapp and other apps who have this feature already. Conventionally, authentication has been done with emails and social login platforms. Only a few apps used the Phone Number Auth feature. Now that it's live on Firebase, let's see how to integrate it into our apps.

Getting Started

1. Connect Firebase to your Android project

• On your Android Studio tools menu, select Firebase. This shows you an Assistant menu to connect your Android app with Firebase.

• On the Firebase Assistant Menu, select Authentication.
• Click on Connect to Firebase to connect your app with any of your Firebase Projects.

• From the dialog, select the Firebase project you wish to connect your app with and click Connect to Firebase.

• Set your app’s SHA-1 hash in the Firebase console. See Authenticating Your Client for information about finding your app’s SHA-1 hash.

2. Configure Firebase Authentication

• Add the dependency for Firebase Authentication to your app-level build.gradle file:

`compile `com.google.firebase:firebase-auth:11.8.0``

3. Enable Phone Number sign-in for your Firebase project

To be able to authenticate user by SMS , you must first enable Phone Number sign-in method in your Firebase console and click save.

4. Send a verification code to the user’s phone

To initialize the sign-in process, present the user a screen to input his/her phone number. Also note: always let the user know they might receive an SMS message for verification and standard rates apply. For this post, we will be use Firebase UI.

Then, pass their phone number to the PhoneAuthProvider.verifyPhoneNumber method to request that Firebase verify the user's phone number. For example:

PhoneAuthProvider.getInstance().verifyPhoneNumber( phoneNumber, // Phone number to verify 60, // Timeout duration TimeUnit.SECONDS, // Unit of timeout this, // Activity (for callback binding) mCallbacks); // OnVerificationStateChangedCallbacks

When you call PhoneAuthProvider.verifyPhoneNumber, you must also provide an instance of OnVerificationStateChangedCallbacks, which contains implementations of the callback functions that handle the results of the request. For example:

onCodeSent This callback is called when the SMS verification code has been sent to the provided phone number.

@Override
public void onCodeSent(String verificationId,
PhoneAuthProvider.ForceResendingToken token) {
Log.d(TAG, “onCodeSent:” + verificationId);
// Save verification ID and resending token so we can use them later
mVerificationId = verificationId;
mResendToken = token;
// …

}

Create a PhoneAuthCredential object

Create a PhoneAuthCredential object, using the verification code and the verification ID that was passed to the onCodeSent.

PhoneAuthCredential credential = PhoneAuthProvider.getCredential(verificationId, code);

5. Sign-In User

Complete the sign-in flow by passing the PhoneAuthCredential object to FirebaseAuth.signInWithCredential:

mAuth.signInWithCredential(credential) .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() { @Override public void onComplete(@NonNull Task<AuthResult> task) { if (task.isSuccessful()) { // Sign in success, update UI with the signed-in user's information Log.d(TAG, "signInWithCredential:success"); FirebaseUser user = task.getResult().getUser(); startActivity(new Intent(getApplicationContext(), Main2Activity.class)); } else { // Sign in failed, display a message and update the UI Log.w(TAG, "signInWithCredential:failure", task.getException()); if (task.getException() instanceof FirebaseAuthInvalidCredentialsException) { // The verification code entered was invalid smsCodeVerificationField.setError("Invalid code."); } } } });

This post is originally published by the author here. This version has been edited for clarity and may appear different from the original post.