Google Signing using Firebase Authentication in Android

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Firebase is a mobile and web application development platform. It provides services that a web application or mobile application might require. Firebase provides email and password authentication without any overhead of building the backend for user authentication. Google Sign-In is a secure way to authenticate users in your apps. It reduces the hassle of dealing with and handling those extra passwords by the user to get authenticated into the app. Firebase offers a great number of options to implement Login in your app like Email, Phone number, Google, Facebook, etc.

What We Are Going to Build in this Article?

Here is a sample video of what we are going to build in this article. We will be implementing this application in both Java and Kotlin Programming Languages for Android.

Step By Step Implementation

Step 1: Create a New Project in Android Studio

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. The code for that has been given in both Java and Kotlin Programming Language for Android.

Step 2: Connecting Firebase with the Application

Navigate to the Website.
Go to the Console.
Add Project.

Name your project and click on continue and Connect your firebase to your google account.

After completion of the project, the following interface will appear.

Now enter the package name and the name of your application. To enter the SHA-1 value follow the steps:

Go to Gradle > Task > android >  signing report

After opening the signing report you will get the value of SHA-1 as shown below. Copy it and use it in firebase.

After completing the above step download the google-services.json config file provided there and paste it into android studio.

Navigate to project  > app > src and paste it

Go to authentication.

Go to Sign-in-method and enable google sign-in.

Step 3: Adding Required Dependencies & Plugins

Navigate to Gradle Scripts > build.gradle(project) and add the following dependency to it:

classpath 'com.google.gms:google-services:4.3.10'

Navigate to Gradle Scripts > build.gradle(module) and add the following plugin to it:

apply plugin: 'com.google.gms.google-services'

Navigate to Gradle Scripts > build.gradle(module) and add the following dependencies in it:

implementation 'com.google.firebase:firebase-auth:19.4.0'
implementation 'com.google.android.gms:play-services-auth:18.1.0'
implementation 'com.github.bumptech.glide:glide:4.11.0'

Step 4: Adding Internet Permission

Go to the AndroidManifest.xml file and add the following piece of code to it-

<uses-permission android:name="android.permission.INTERNET"/>

Step 5: Working with XML Files

Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file.

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
  
    <com.google.android.gms.common.SignInButton
        android:id="@+id/bt_sign_in"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="16dp" />
</RelativeLayout>

Navigate to app > right-click > new > activity > empty activity and name it as ProfileActivity. Use the following code in the activity_profile.xml file.

XML

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context=".ProfileActivity">
  
    <ImageView
        android:id="@+id/iv_image"
        android:layout_width="150dp"
        android:layout_height="150dp" />
  
    <TextView
        android:id="@+id/tv_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="@color/design_default_color_primary"
        android:textSize="24sp"
        android:textStyle="bold" />
  
    <Button
        android:id="@+id/bt_logout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:text="Logout" />
</LinearLayout>

Step 6: Working with MainActivity File

Go to the MainActivity file and refer to the following code. Below is the code for the MainActivity.java file. Comments are added inside the code to understand the code in more detail.

Java

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import com.google.android.gms.auth.api.signin.GoogleSignIn;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInClient;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.common.SignInButton;
import com.google.android.gms.common.api.ApiException;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthCredential;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.auth.GoogleAuthProvider;
  
public class MainActivity extends AppCompatActivity {
    // Initialize variables
    SignInButton btSignIn;
    GoogleSignInClient googleSignInClient;
    FirebaseAuth firebaseAuth;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
  
        // Assign variable
        btSignIn = findViewById(R.id.bt_sign_in);
  
        // Initialize sign in options the client-id is copied form google-services.json file
        GoogleSignInOptions googleSignInOptions = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken("438431947620-ecpi41uk3dhhf4mv8g8q993k3vs49ltm.apps.googleusercontent.com")
                .requestEmail()
                .build();
  
        // Initialize sign in client
        googleSignInClient = GoogleSignIn.getClient(MainActivity.this, googleSignInOptions);
  
        btSignIn.setOnClickListener((View.OnClickListener) view -> {
            // Initialize sign in intent
            Intent intent = googleSignInClient.getSignInIntent();
            // Start activity for result
            startActivityForResult(intent, 100);
        });
  
        // Initialize firebase auth
        firebaseAuth = FirebaseAuth.getInstance();
        // Initialize firebase user
        FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();
        // Check condition
        if (firebaseUser != null) {
            // When user already sign in redirect to profile activity
            startActivity(new Intent(MainActivity.this, ProfileActivity.class).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK));
        }
    }
  
    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        // Check condition
        if (requestCode == 100) {
            // When request code is equal to 100 initialize task
            Task<GoogleSignInAccount> signInAccountTask = GoogleSignIn.getSignedInAccountFromIntent(data);
            // check condition
            if (signInAccountTask.isSuccessful()) {
                // When google sign in successful initialize string
                String s = "Google sign in successful";
                // Display Toast
                displayToast(s);
                // Initialize sign in account
                try {
                    // Initialize sign in account
                    GoogleSignInAccount googleSignInAccount = signInAccountTask.getResult(ApiException.class);
                    // Check condition
                    if (googleSignInAccount != null) {
                        // When sign in account is not equal to null initialize auth credential
                        AuthCredential authCredential = GoogleAuthProvider.getCredential(googleSignInAccount.getIdToken(), null);
                        // Check credential
                        firebaseAuth.signInWithCredential(authCredential).addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                            @Override
                            public void onComplete(@NonNull Task<AuthResult> task) {
                                // Check condition
                                if (task.isSuccessful()) {
                                    // When task is successful redirect to profile activity display Toast
                                    startActivity(new Intent(MainActivity.this, ProfileActivity.class).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK));
                                    displayToast("Firebase authentication successful");
                                } else {
                                    // When task is unsuccessful display Toast
                                    displayToast("Authentication Failed :" + task.getException().getMessage());
                                }
                            }
                        });
                    }
                } catch (ApiException e) {
                    e.printStackTrace();
                }
            }
        }
    }
  
    private void displayToast(String s) {
        Toast.makeText(getApplicationContext(), s, Toast.LENGTH_SHORT).show();
    }
}

Kotlin

import android.content.Intent
import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import com.google.android.gms.auth.api.signin.GoogleSignIn
import com.google.android.gms.auth.api.signin.GoogleSignInAccount
import com.google.android.gms.auth.api.signin.GoogleSignInClient
import com.google.android.gms.auth.api.signin.GoogleSignInOptions
import com.google.android.gms.common.SignInButton
import com.google.android.gms.common.api.ApiException
import com.google.android.gms.tasks.Task
import com.google.firebase.auth.AuthCredential
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.FirebaseUser
import com.google.firebase.auth.GoogleAuthProvider
  
class MainActivity : AppCompatActivity() {
    // Initialize variables
    lateinit var btSignIn: SignInButton
    lateinit var googleSignInClient: GoogleSignInClient
    private lateinit var firebaseAuth: FirebaseAuth
  
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // Assign variable
        btSignIn = findViewById(R.id.bt_sign_in)
  
        // Initialize sign in options the client-id is copied form google-services.json file
        val googleSignInOptions = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
            .requestIdToken("438431947620-ecpi41uk3dhhf4mv8g8q993k3vs49ltm.apps.googleusercontent.com")
            .requestEmail()
            .build()
  
        // Initialize sign in client
        googleSignInClient = GoogleSignIn.getClient(this@MainActivity, googleSignInOptions)
        btSignIn.setOnClickListener { // Initialize sign in intent
            val intent: Intent = googleSignInClient.signInIntent
            // Start activity for result
            startActivityForResult(intent, 100)
        }
  
        // Initialize firebase auth
        firebaseAuth = FirebaseAuth.getInstance()
        // Initialize firebase user
        val firebaseUser: FirebaseUser? = firebaseAuth.currentUser
        // Check condition
        if (firebaseUser != null) {
            // When user already sign in redirect to profile activity
            startActivity(
                Intent(
                    this@MainActivity,
                    ProfileActivity::class.java
                ).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
            )
        }
    }
  
    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        // Check condition
        if (requestCode == 100) {
            // When request code is equal to 100 initialize task
            val signInAccountTask: Task<GoogleSignInAccount> =
                GoogleSignIn.getSignedInAccountFromIntent(data)
  
            // check condition
            if (signInAccountTask.isSuccessful) {
                // When google sign in successful initialize string
                val s = "Google sign in successful"
                // Display Toast
                displayToast(s)
                // Initialize sign in account
                try {
                    // Initialize sign in account
                    val googleSignInAccount = signInAccountTask.getResult(ApiException::class.java)
                    // Check condition
                    if (googleSignInAccount != null) {
                        // When sign in account is not equal to null initialize auth credential
                        val authCredential: AuthCredential = GoogleAuthProvider.getCredential(
                            googleSignInAccount.idToken, null
                        )
                        // Check credential
                        firebaseAuth.signInWithCredential(authCredential)
                            .addOnCompleteListener(this) { task ->
                                // Check condition
                                if (task.isSuccessful) {
                                    // When task is successful redirect to profile activity
                                    startActivity(
                                        Intent(
                                            this@MainActivity,
                                            ProfileActivity::class.java
                                        ).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
                                    )
                                    // Display Toast
                                    displayToast("Firebase authentication successful")
                                } else {
                                    // When task is unsuccessful display Toast
                                    displayToast(
                                        "Authentication Failed :" + task.exception.message
                                    )
                                }
                            }
                    }
                } catch (e: ApiException) {
                    e.printStackTrace()
                }
            }
        }
    }
  
    private fun displayToast(s: String) {
        Toast.makeText(applicationContext, s, Toast.LENGTH_SHORT).show()
    }
}

Go to the ProfileActivity file and use the following code in it:

Java

import android.os.Bundle;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import com.bumptech.glide.Glide;
import com.google.android.gms.auth.api.signin.GoogleSignIn;
import com.google.android.gms.auth.api.signin.GoogleSignInClient;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
  
public class ProfileActivity extends AppCompatActivity {
    // Initialize variable
    ImageView ivImage;
    TextView tvName;
    Button btLogout;
    FirebaseAuth firebaseAuth;
    GoogleSignInClient googleSignInClient;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_profile);
  
        // Assign variable
        ivImage = findViewById(R.id.iv_image);
        tvName = findViewById(R.id.tv_name);
        btLogout = findViewById(R.id.bt_logout);
  
        // Initialize firebase auth
        firebaseAuth = FirebaseAuth.getInstance();
  
        // Initialize firebase user
        FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();
  
        // Check condition
        if (firebaseUser != null) {
            // When firebase user is not equal to null set image on image view
            Glide.with(ProfileActivity.this).load(firebaseUser.getPhotoUrl()).into(ivImage);
            // set name on text view
            tvName.setText(firebaseUser.getDisplayName());
        }
  
        // Initialize sign in client
        googleSignInClient = GoogleSignIn.getClient(ProfileActivity.this, GoogleSignInOptions.DEFAULT_SIGN_IN);
  
        btLogout.setOnClickListener(view -> {
            // Sign out from google
            googleSignInClient.signOut().addOnCompleteListener(new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    // Check condition
                    if (task.isSuccessful()) {
                        // When task is successful sign out from firebase
                        firebaseAuth.signOut();
                        // Display Toast
                        Toast.makeText(getApplicationContext(), "Logout successful", Toast.LENGTH_SHORT).show();
                        // Finish activity
                        finish();
                    }
                }
            });
        });
    }
}

Kotlin

import android.os.Bundle
import android.widget.Button
import android.widget.ImageView
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import com.bumptech.glide.Glide
import com.google.android.gms.auth.api.signin.GoogleSignIn
import com.google.android.gms.auth.api.signin.GoogleSignInClient
import com.google.android.gms.auth.api.signin.GoogleSignInOptions
import com.google.firebase.auth.FirebaseAuth
  
class ProfileActivity : AppCompatActivity() {
    // Initialize variable
    lateinit var ivImage: ImageView
    lateinit var tvName: TextView
    lateinit var btLogout: Button
    lateinit var firebaseAuth: FirebaseAuth
    lateinit var googleSignInClient: GoogleSignInClient
  
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_profile)
  
        // Assign variable
        ivImage = findViewById(R.id.iv_image)
        tvName = findViewById(R.id.tv_name)
        btLogout = findViewById(R.id.bt_logout)
  
        // Initialize firebase auth
        firebaseAuth = FirebaseAuth.getInstance()
  
        // Initialize firebase user
        val firebaseUser = firebaseAuth.currentUser
  
        // Check condition
        if (firebaseUser != null) {
            // When firebase user is not equal to null set image on image view
            Glide.with(this@ProfileActivity).load(firebaseUser.photoUrl).into(ivImage)
            // set name on text view
            tvName.text = firebaseUser.displayName
        }
  
        // Initialize sign in client
        googleSignInClient = GoogleSignIn.getClient(this@ProfileActivity, GoogleSignInOptions.DEFAULT_SIGN_IN)
        btLogout.setOnClickListener {
            // Sign out from google
            googleSignInClient.signOut().addOnCompleteListener { task ->
                // Check condition
                if (task.isSuccessful) {
                    // When task is successful sign out from firebase
                    firebaseAuth.signOut()
                    // Display Toast
                    Toast.makeText(applicationContext, "Logout successful", Toast.LENGTH_SHORT).show()
                    // Finish activity
                    finish()
                }
            }
        }
    }
}