Mobile Authentication

String phoneNum = "+16505554567";
String testVerificationCode = "123456";

// Whenever verification is triggered with the whitelisted number,
// provided it is not set for auto-retrieval, onCodeSent will be triggered.
PhoneAuthProvider.getInstance().verifyPhoneNumber(
        phoneNum, 30L /*timeout*/, TimeUnit.SECONDS,
        this, new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {

            @Override
            public void onCodeSent(String verificationId,
                                   PhoneAuthProvider.ForceResendingToken forceResendingToken) {
                // Save the verification id somewhere
                // ...

                // The corresponding whitelisted code above should be used to complete sign-in.
                MainActivity.this.enableUserManuallyInputCode();
            }

            @Override
            public void onVerificationCompleted(PhoneAuthCredential phoneAuthCredential) {
                // Sign in with the credential
                // ...
            }

            @Override
            public void onVerificationFailed(FirebaseException e) {
                 // ...
            }

        });