firebase google sign in android example

 firebase google signing :

google signing Activity .Java code :

public class LoginActivity extends AppCompatActivity {

    private static final String TAG = "LoginActivity";
    private static final int RC_SIGN_IN = 1001;
    GoogleSignInClient googleSignInClient;
    private FirebaseAuth firebaseAuth;

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

        SignInButton signInButton = findViewById(R.id.sign_in_button);
        signInButton.setOnClickListener(new View.OnClickListener() {
            @Override public void onClick(View view) {
                signInToGoogle();
            }
        });
        configureGoogleClient();
    }


    private void configureGoogleClient() {

        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(getString(R.string.default_web_client_idd))
                .requestEmail()
                .build();

        googleSignInClient = GoogleSignIn.getClient(this, gso);

        SignInButton signInButton = findViewById(R.id.sign_in_button);
        signInButton.setSize(SignInButton.SIZE_WIDE);

        firebaseAuth = FirebaseAuth.getInstance();
    }
    @Override
    public void onStart() {
        super.onStart();
        FirebaseUser currentUser = firebaseAuth.getCurrentUser();
        if (currentUser != null) {
            Log.d(TAG, "Currently Signed in: " + currentUser.getEmail());
            //showToastMessage("Currently Logged in: " + currentUser.getEmail());
            launchMainActivity(currentUser);
        }
    }
    public void signInToGoogle() {
        Intent signInIntent = googleSignInClient.getSignInIntent();
        startActivityForResult(signInIntent, RC_SIGN_IN);
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == RC_SIGN_IN) {
            Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
            try {
                GoogleSignInAccount account = task.getResult(ApiException.class);
                showToastMessage("Google Sign in Succeeded");
                firebaseAuthWithGoogle(account);
            } catch (ApiException e) {
                Log.w(TAG, "Google sign in failed", e);
                showToastMessage("Google Sign in Failed " + e);
            }
        }
    }
    private void firebaseAuthWithGoogle(GoogleSignInAccount account) {
        Log.d(TAG, "firebaseAuthWithGoogle:" + account.getId());
        AuthCredential credential = GoogleAuthProvider.getCredential(account.getIdToken(), null);
        firebaseAuth.signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                            FirebaseUser user = firebaseAuth.getCurrentUser();
                            Log.d(TAG, "signInWithCredential:success: currentUser: " + user.getEmail());
                            showToastMessage("Firebase Authentication Succeeded ");
                            launchMainActivity(user);
                        } else {
                            Log.w(TAG, "signInWithCredential:failure", task.getException());
                            showToastMessage("Firebase Authentication failed:" + task.getException());
                        }
                    }
                });
    }
    private void showToastMessage(String message) {
        Toast.makeText(LoginActivity.this, message, Toast.LENGTH_LONG).show();
    }
    private void launchMainActivity(FirebaseUser user) {
        if (user != null) {
            MapsActivity.startActivity(this, user.getDisplayName());
            finish();
        }
    }
}

google signing Activity .XML code :
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".LoginActivity">

    <com.google.android.gms.common.SignInButton
        android:id="@+id/sign_in_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

    </com.google.android.gms.common.SignInButton>

</androidx.constraintlayout.widget.ConstraintLayout>
default_web_client_idd for Google signing :
<string name="default_web_client_idd" 
    translatable="false">842131502487-733sm2dfhj08mblmvva1nf0cselfoo1e.apps.googleusercontent.com</string>