Google Sign In in Android Studio example | How To Integrate Google Login In android App

This Is the part 4  of our youtube tutorial series in android development  In last part we covered how to  login with email  and  password using firebase authentication so in this  video tutorial  we  are gonna  see how to Integrate Google Login in just 7 Steps. 

Step 1.

So  to Integrate Google  Login In  your android project first of all you will need to add this library in your app level  build.gradle file  and sync the project

  implementation 'com.google.android.gms:play-services-auth:20.0.1'

Step 2.

In this step  we will  add a  SignInButton  In our xml file and this signinbutton  class is available in above library so we just have to use it. 

sign in  button xml code.

 
   <com.google.android.gms.common.SignInButton
        android:id="@+id/sign_in_with_google"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

Step 3.

In this step we will initialize all views so we have  only one view in our activity_main.xml file so  we will initialize  it this way.

SignInButton signInButton = findViewById(R.id.sign_in_with_google);
        

Step 4.

In this step we will create instance of GoogleSignInClient & GoogleSignInOptions class 

 private GoogleSignInClient mGoogleSignInClient;   

/// write this code in onCreate Activity Method
GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(getString(R.string.default_web_client_id))
                .requestEmail()
                .build();

mGoogleSignInClient = GoogleSignIn.getClient(this, gso);
 

Step 5.

In this Step we  will discuss how start an activity for result. as i already discuess  above startActivityForResult(intent,REQUEST_CODE); method has been deprecated so we will what is the alternative of this method
so to start and activity for result we will first create a internal class GetGoogleLoginDetails that will extend with ActivityResultContract.

    public class GetGoogleLoginDetails extends ActivityResultContract<Integer, Intent> {
        @NonNull
        @Override
        public Intent createIntent(@NonNull Context context, @NonNull Integer requestCode) {
            // in this overrirde method simply return required intent
            Intent signInIntent = mGoogleSignInClient.getSignInIntent();
            return signInIntent;
        }


        @Override
        public Intent parseResult(int resultCode, @Nullable Intent result) {
             // in this overrirde method you can filter results
            if (resultCode != Activity.RESULT_OK || result == null) {
                return null;
            }
            return result;
        }
    }

Step 6.
In this step we will create ActivityResultLauncher make sure to  add ActivityResultLauncher in your oncreate method of an 
activity or a fragment class. ActivityResultLauncher will give results inside onActivityResult Method and we will get intent result as a parameter of this metod
we will use this  intent to get GoogleSignInAccount Details as you can see in code below.

  ActivityResultLauncher activity_result_launcher = registerForActivityResult(new GetGoogleLoginDetails(), new ActivityResultCallback() {
            @Override
            public void onActivityResult(Intent result) {
                Task task = GoogleSignIn.getSignedInAccountFromIntent(result);
                try {
                    // Google Sign In was successful, authenticate with Firebase
                    GoogleSignInAccount account = task.getResult(ApiException.class);
                    Log.d(TAG, "firebaseAuthWithGoogle:" + account.getId());
                    Toast.makeText(MainActivity.this, "Data Recieved " + account.getDisplayName(), Toast.LENGTH_SHORT).show();

                    firebaseAuthWithGoogle(account.getIdToken());
                } catch (ApiException e) {
                    // Google Sign In failed, update UI appropriately
                    Log.w(TAG, "Google sign in failed", e);
                }
            }
        });

Step 7.

Add click listener on sign in button and call ActivityResultLauncher lanch method inside this listener.

  signInButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                activity_result_launcher.launch(12);

            }
        });        
    

As you can  see in step 6 we called firebaseAuthWithGoogle(account.getIdToken()); method but we have not created it yet
so in this step we will se how this method will work.
In firebaseAuthWithGoogle method simply use idToken and create AuthCredential and then we use credential to login  user to firebase
if you are not using firebase auth to manage users account then you don't need to write below code you can simply get signed in user details 
in side onactivity result method by calling account.getEmail() and then store this email on your server . 

private void firebaseAuthWithGoogle(String idToken) {
        AuthCredential credential = GoogleAuthProvider.getCredential(idToken, null);
        FirebaseAuth.getInstance().signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener() {
                    @Override
                    public void onComplete(@NonNull Task task) {
                        if (task.isSuccessful()) {
                            // Sign in success, update UI with the signed-in user's information
                            Log.d(TAG, "signInWithCredential:success");
                            FirebaseUser user = mAuth.getCurrentUser();

                        } else {
                            // If sign in fails, display a message to the user.
                            Log.w(TAG, "signInWithCredential:failure", task.getException());
                       //     updateUI(null);
                        }
                    }
                });
    }