FA PHONE HandlingCallBacks

        //the callback to detect the verification status
        private PhoneAuthProvider.OnVerificationStateChangedCallbacks mCallbacks =
                new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {
            public void onVerificationCompleted(PhoneAuthCredential phoneAuthCredential) {
                //Getting the code sent by SMS
                String code = phoneAuthCredential.getSmsCode();

                //sometime the code is not detected automatically
                //in this case the code will be null
                //so user has to manually enter the code
                if (code != null) {
                    //verifying the code

            public void onVerificationFailed(FirebaseException e) {
                Toast.makeText(VerifyPhoneActivity.this, e.getMessage(), Toast.LENGTH_LONG).show();
                Log.i(TAG, "onVerificationFailed: " + e.getLocalizedMessage());

            //when the code is generated then this method will receive the code.
            public void onCodeSent(String s, PhoneAuthProvider.ForceResendingToken forceResendingToken) {
//                super.onCodeSent(s, forceResendingToken);

                //storing the verification id that is sent to the user
                mVerificationId = s;

        private void verifyVerificationCode(String code) {
            //creating the credential
            PhoneAuthCredential credential = PhoneAuthProvider.getCredential(mVerificationId, code);