Phone Auth Using Firebase

PhoneAuth.java

package com.kantapp.myfireapp.Activity;

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.FirebaseException;
import com.google.firebase.FirebaseTooManyRequestsException;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseAuthInvalidCredentialsException;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.auth.PhoneAuthCredential;
import com.google.firebase.auth.PhoneAuthProvider;
import com.kantapp.myfireapp.MainActivity;
import com.kantapp.myfireapp.R;

import java.util.concurrent.TimeUnit;

public class PhoneAuth extends AppCompatActivity {
    private static final String TAG = "PhoneAuth";
    private TextView textView;
    private FirebaseAuth auth;
    EditText mPhoneNumberField, mVerificationField;
    Button mStartButton, mVerifyButton, mResendButton;
    private PhoneAuthProvider.ForceResendingToken mResendToken;
    private PhoneAuthProvider.OnVerificationStateChangedCallbacks mCallbacks;
    String mVerificationId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_phone_auth);

        textView=findViewById(R.id.mobileNo);
        auth=FirebaseAuth.getInstance();

        mPhoneNumberField = (EditText) findViewById(R.id.field_phone_number);
        mVerificationField = (EditText) findViewById(R.id.field_verification_code);

        mStartButton = (Button) findViewById(R.id.button_start_verification);
        mVerifyButton = (Button) findViewById(R.id.button_verify_phone);
        mResendButton = (Button) findViewById(R.id.button_resend);

        mStartButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!validatePhoneNumber()) {
                    return;
                }
                startPhoneNumberVerification(mPhoneNumberField.getText().toString());
            }
        });
        mVerifyButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String code = mVerificationField.getText().toString();
                if (TextUtils.isEmpty(code)) {
                    mVerificationField.setError("Cannot be empty.");
                    return;
                }

                verifyPhoneNumberWithCode(mVerificationId, code);
            }
        });
        mResendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                resendVerificationCode(mPhoneNumberField.getText().toString(), mResendToken);
            }
        });

        mCallbacks=new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {
            @Override
            public void onVerificationCompleted(PhoneAuthCredential phoneAuthCredential) {
                Log.d(TAG, "onVerificationCompleted:" + phoneAuthCredential);
                signInWithPhoneAuthCredential(phoneAuthCredential);
            }

            @Override
            public void onVerificationFailed(FirebaseException e) {
                Log.w(TAG, "onVerificationFailed", e);
                if (e instanceof FirebaseAuthInvalidCredentialsException)
                {
                    mPhoneNumberField.setError("Invalid phone number.");
                } else if (e instanceof FirebaseTooManyRequestsException)
                {
                    Snackbar.make(findViewById(android.R.id.content), "Quota exceeded.",
                            Snackbar.LENGTH_SHORT).show();
                }
            }

            @Override
            public void onCodeSent(String s, PhoneAuthProvider.ForceResendingToken forceResendingToken) {
                Log.d(TAG, "onCodeSent:" + s);
                mVerificationId = s;
                mResendToken = forceResendingToken;
            }
        };


    }
    private boolean validatePhoneNumber() {
        String phoneNumber = mPhoneNumberField.getText().toString();
        if (TextUtils.isEmpty(phoneNumber)) {
            mPhoneNumberField.setError("Invalid phone number.");
            return false;
        }
        return true;
    }



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

    private void verifyPhoneNumberWithCode(String mVerificationId, String code) {
        PhoneAuthCredential credential = PhoneAuthProvider.getCredential(mVerificationId, code);
        signInWithPhoneAuthCredential(credential);
    }

    private void resendVerificationCode(String phoneNumber, PhoneAuthProvider.ForceResendingToken mResendToken) {
        PhoneAuthProvider.getInstance().verifyPhoneNumber(
                phoneNumber,        // Phone number to verify
                60,                 // Timeout duration
                TimeUnit.SECONDS,   // Unit of timeout
                this,               // Activity (for callback binding)
                mCallbacks,         // OnVerificationStateChangedCallbacks
                mResendToken);             // ForceResendingToken from callbacks
    }

    private void signInWithPhoneAuthCredential(PhoneAuthCredential phoneAuthCredential) {
        auth.signInWithCredential(phoneAuthCredential)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                            Log.d(TAG, "signInWithCredential:success");
                            FirebaseUser user = task.getResult().getUser();
                            startActivity(new Intent(getApplicationContext(), MainActivity.class));
                            finish();
                        } else {
                            Log.w(TAG, "signInWithCredential:failure", task.getException());
                            if (task.getException() instanceof FirebaseAuthInvalidCredentialsException) {
                                mVerificationField.setError("Invalid code.");
                            }
                        }
                    }
                });

    }

    @Override
    protected void onStart() {
        super.onStart();
        if(auth.getCurrentUser()!=null)
        {
            textView.setText(auth.getCurrentUser().getPhoneNumber());
        }
    }
}