Firebase not sending verification code to phone the second time

Question

In my app, I'm using Firebase to verify the user's phone number. However, the verification system is inconsistent and sends the OTP only the first time. For example, I get the OTP when I'm signing in for the first time, but if I sign out and try to sign in again, I don't get the OTP.

This is the activity where the user is asked to enter the OTP:

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import com.google.firebase.FirebaseException;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.PhoneAuthCredential;
import com.google.firebase.auth.PhoneAuthProvider;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.QueryDocumentSnapshot;
import com.google.firebase.firestore.QuerySnapshot;
import com.google.firebase.iid.FirebaseInstanceId;
import com.google.firebase.iid.InstanceIdResult;

import java.util.concurrent.TimeUnit;

public class EnterOTPActivity extends AppCompatActivity {
    String userPhoneNumber;

    private int autoResendCount=0, resumeCount=0;
    private final String ctryCode = "+91";
    private String verificationId;
    private FirebaseAuth mAuth;
    private TextView resendOtp, enterOtpMessage, timerTV;
    private ProgressDialog progressDialog;
    private EditText otpField;
    private boolean firstSend=true,timerOn=true;
    FirebaseFirestore db;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_enter_otp);
        mAuth = FirebaseAuth.getInstance();
        otpField = findViewById(R.id.editTextOtp);
        resendOtp =  findViewById(R.id.resendOTPButton);
        timerTV = findViewById(R.id.resendTimer);
        userPhoneNumber = getIntent().getStringExtra("USER_MOB").trim();
        sendVerificationCode(userPhoneNumber);
        startResendTimer(15);
        getSupportActionBar().setTitle("Verification");
        resendOtp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (!timerOn) {
                    startResendTimer(30);
                    firstSend = false;
                    sendVerificationCode(userPhoneNumber);
                }
            }
        });
        FloatingActionButton next = findViewById(R.id.fab2);
        enterOtpMessage =  findViewById(R.id.aboutotpverif);
        enterOtpMessage.setText(enterOtpMessage.getText().toString() + " " + ctryCode + userPhoneNumber);
        progressDialog = new ProgressDialog(this);
        progressDialog.setMessage("Please wait while we check your verification code");
        progressDialog.setTitle("Verification");
        progressDialog.setCancelable(false);
        next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //check if otp is correct here
                if (otpField.getText().toString().length() == 6) {
                    verifyCode(otpField.getText().toString().trim());
                    if(!progressDialog.isShowing())
                    progressDialog.show();
                } else {
                    View parentLayout = findViewById(android.R.id.content);
                    Snackbar.make(parentLayout, "A valid verification code has 6 digits", Snackbar.LENGTH_SHORT)
                            .setAction("OKAY", new View.OnClickListener() {
                                @Override
                                public void onClick(View view) {

                                }
                            })
                            .setActionTextColor(getResources().getColor(android.R.color.holo_red_light))
                            .show();
                }
            }
        });
    }

    private void verifyCode(String code) {

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

        }
        catch (Exception e) {
            // code here is executed when we don't get the OTP and enter a wrong one
            progressDialog.dismiss();
            progressDialog.setCancelable(true);
            View parentLayout = findViewById(android.R.id.content);
            Snackbar.make(parentLayout, getString(R.string.incorrect_code_t1), Snackbar.LENGTH_LONG)
                    .setAction("OKAY", new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {

                        }
                    })
                    .setActionTextColor(getResources().getColor(android.R.color.holo_red_light))
                    .show();
            if(progressDialog.isShowing())
            progressDialog.dismiss();
        }
    }

    private void signInwithCredential(PhoneAuthCredential credential) {
        mAuth.signInWithCredential(credential).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (task.isSuccessful()) {
                    isRegisteredUser();
                }
                else {
                    if(progressDialog.isShowing())
                    progressDialog.dismiss();
                    View parentLayout = findViewById(android.R.id.content);
                    Snackbar.make(parentLayout, "Incorrect verification code", Snackbar.LENGTH_SHORT)
                            .setAction("OKAY", new View.OnClickListener() {
                                @Override
                                public void onClick(View view) {

                                }
                            })
                            .setActionTextColor(getResources().getColor(android.R.color.holo_red_light))
                            .show();
                    if(progressDialog.isShowing())
                    progressDialog.dismiss();

                }
            }
        });

    }

    private void sendVerificationCode(String number) {
        final String phoneNumber = ctryCode + number;
        PhoneAuthProvider.getInstance().verifyPhoneNumber(
                phoneNumber,        // Phone number to verify
                120,                 // Timeout duration
                TimeUnit.SECONDS,   // Unit of timeout
                this,               // Activity (for callback binding)
                mCallbacks);        // OnVerificationStateChangedCallbacks
    }

    private PhoneAuthProvider.OnVerificationStateChangedCallbacks mCallbacks = new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {

        @Override
        public void onCodeSent(@NonNull String s, @NonNull PhoneAuthProvider.ForceResendingToken forceResendingToken) {
            super.onCodeSent(s, forceResendingToken);
            verificationId = s;
        }

        @Override
        public void onVerificationCompleted(@NonNull PhoneAuthCredential phoneAuthCredential) {
            String code = phoneAuthCredential.getSmsCode();
            if (code != null) {
                verifyCode(code);
                otpField.setText(code);
                if(!progressDialog.isShowing())
                progressDialog.show();
            }
        }

        @Override
        public void onVerificationFailed(@NonNull FirebaseException e) {
            Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
        }
    };

    private void isRegisteredUser() {

        final String userId = ctryCode + userPhoneNumber;
        db = FirebaseFirestore.getInstance();
        db.collection("users")
                .whereEqualTo("phone", userId)
                .get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {

                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
                        try{
                        if (task.isSuccessful()) {

                            saveToken(userId);

                            for (QueryDocumentSnapshot document : task.getResult()) {
                                if (document.getId().equalsIgnoreCase(userId)) {

                                    Intent startmainact = new Intent(EnterOTPActivity.this, MainActivity.class);
                                    startmainact.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
                                    startActivity(startmainact);
                                    finish();
                                    return;
                                }
                                //Log.d(TAG, document.getId() + " => " + document.getData());
                            }

                            Intent startposact = new Intent(EnterOTPActivity.this, ParOrStudActivity.class);

                            startposact.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
                            startActivity(startposact);
                            finish();

                        } else {
                            View parentLayout = findViewById(android.R.id.content);
                            Snackbar.make(parentLayout, "Database error: please try again", Snackbar.LENGTH_SHORT)
                                    .setAction("OKAY", new View.OnClickListener() {
                                        @Override
                                        public void onClick(View view) {

                                        }
                                    })
                                    .setActionTextColor(getResources().getColor(android.R.color.holo_red_light))
                                    .show();
                        }
                    }
                        catch(Exception e){
                            View parentLayout = findViewById(android.R.id.content);
                            Snackbar.make(parentLayout, "Database error: please try again", Snackbar.LENGTH_SHORT)
                                    .setAction("OKAY", new View.OnClickListener() {
                                        @Override
                                        public void onClick(View view) {

                                        }
                                    })
                                    .setActionTextColor(getResources().getColor(android.R.color.holo_red_light))
                                    .show();
                        }
                    }

                });
    }

    private void saveToken(final String userId) {
        FirebaseInstanceId.getInstance().getInstanceId()
                .addOnCompleteListener(new OnCompleteListener<InstanceIdResult>() {
                    @Override
                    public void onComplete(@NonNull Task<InstanceIdResult> task) {
                        if (!task.isSuccessful()) {
                            return;
                        }

                        // Get new Instance ID token
                        String token = task.getResult().getToken();
                        FirebaseFirestore.getInstance().collection("users").document(userId).update("token",token);
                    }
                });
    }


    @Override
    protected void onResume() {
        super.onResume();
        if (autoResendCount<2 && resumeCount>0) {
            sendVerificationCode(userPhoneNumber);
            autoResendCount=autoResendCount+1;
            resumeCount=resumeCount+1;
        }
    }


    @Override
    protected void onStop() {
        super.onStop();
        progressDialog.dismiss();
    }

    public void startResendTimer(int seconds) {
        timerTV.setVisibility(View.VISIBLE);
        resendOtp.setEnabled(false);

        new CountDownTimer(seconds*1000, 1000) {

            public void onTick(long millisUntilFinished) {
                String secondsString = Long.toString(millisUntilFinished/1000);
                if (millisUntilFinished<10000) {
                    secondsString = "0"+secondsString;
                }
                timerTV.setText(" (0:"+ secondsString+")");
            }

            public void onFinish() {
                resendOtp.setEnabled(true);
                timerTV.setVisibility(View.GONE);
                timerOn=false;
            }
        }.start();
    }

    @Override
    public void onBackPressed() {
        // do not allow user to go back to the screen before
    }
}

This erratic verification system delivers an incompetent UX. Is there any way to get around it?

Answer 1

If you read Firebase Docs about PhoneAuthProvider, it is clearly stated:

The verifyPhoneNumber method is reentrant: if you call it multiple times, such as in an activity's onStart method, the verifyPhoneNumber method will not send a second SMS unless the original request has timed out.

In your case, you set the timeout at 120 seconds. If you really want to test this behavior, I suggest reducing the timeout to 10 or 20 seconds, and see if you can resend OTP after the timeout.

Additionally, if you want to get the timeout event, you can add onCodeAutoRetrievalTimeOut as a part of PhoneAuthProvider.OnVerificationStateChangedCallbacks. I think it is safe to set your resendOtp enabled as true in that callback. And it is way better than defining your own timer.