You can let your users authenticate with Firebase using their Google Accounts by integrating Google Sign-In into your app.
Before you begin
- If you haven't already, add Firebase to your Android project.
- In your project-level
build.gradle
file, make sure to include Google's Maven repository in both yourbuildscript
andallprojects
sections. Add the dependencies for the Firebase Authentication Android library and Google Play services to your module (app-level) Gradle file (usually
app/build.gradle
):implementation 'com.google.firebase:firebase-auth:19.2.0' implementation 'com.google.android.gms:play-services-auth:17.0.0'
If you haven't yet specified your app's SHA-1 fingerprint, do so from the Settings page of the Firebase console. Refer to Authenticating Your Client for details on how to get your app's SHA-1 fingerprint.
- Enable Google Sign-In in the Firebase console:
- In the Firebase console, open the Auth section.
- On the Sign in method tab, enable the Google sign-in method and click Save.
Authenticate with Firebase
- Integrate Google Sign-In into your app by following the steps on the
Integrating Google Sign-In into
Your Android App page.
When you configure the
GoogleSignInOptions
object, callrequestIdToken
:Java
// Configure Google Sign In GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN) .requestIdToken(getString(R.string.default_web_client_id)) .requestEmail() .build();
Kotlin
// Configure Google Sign In val gso = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN) .requestIdToken(getString(R.string.default_web_client_id)) .requestEmail() .build()
requestIdToken
method. To find the OAuth 2.0 client ID:- Open the Credentials page in the GCP Console.
- The Web application type client ID is your backend server's OAuth 2.0 client ID.
Java
private void signIn() { Intent signInIntent = mGoogleSignInClient.getSignInIntent(); startActivityForResult(signInIntent, RC_SIGN_IN); }
@Override public void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...); if (requestCode == RC_SIGN_IN) { Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data); try { // Google Sign In was successful, authenticate with Firebase GoogleSignInAccount account = task.getResult(ApiException.class); firebaseAuthWithGoogle(account); } catch (ApiException e) { // Google Sign In failed, update UI appropriately Log.w(TAG, "Google sign in failed", e); // ... } } }
Kotlin
private fun signIn() { val signInIntent = googleSignInClient.signInIntent startActivityForResult(signInIntent, RC_SIGN_IN) }
public override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) { super.onActivityResult(requestCode, resultCode, data) // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...); if (requestCode == RC_SIGN_IN) { val task = GoogleSignIn.getSignedInAccountFromIntent(data) try { // Google Sign In was successful, authenticate with Firebase val account = task.getResult(ApiException::class.java) firebaseAuthWithGoogle(account!!) } catch (e: ApiException) { // Google Sign In failed, update UI appropriately Log.w(TAG, "Google sign in failed", e) // ... } } }
- In your sign-in activity's
onCreate
method, get the shared instance of theFirebaseAuth
object:Java
private FirebaseAuth mAuth; // ... // Initialize Firebase Auth mAuth = FirebaseAuth.getInstance();
Kotlin
private lateinit var auth: FirebaseAuth // ... // Initialize Firebase Auth auth = FirebaseAuth.getInstance()
- When initializing your Activity, check to see if the user is currently signed in:
Java
@Override public void onStart() { super.onStart(); // Check if user is signed in (non-null) and update UI accordingly. FirebaseUser currentUser = mAuth.getCurrentUser(); updateUI(currentUser); }
Kotlin
public override fun onStart() { super.onStart() // Check if user is signed in (non-null) and update UI accordingly. val currentUser = auth.currentUser updateUI(currentUser) }
- After a user successfully signs in, get an ID token from the
GoogleSignInAccount
object, exchange it for a Firebase credential, and authenticate with Firebase using the Firebase credential:Java
private void firebaseAuthWithGoogle(GoogleSignInAccount acct) { Log.d(TAG, "firebaseAuthWithGoogle:" + acct.getId()); AuthCredential credential = GoogleAuthProvider.getCredential(acct.getIdToken(), null); mAuth.signInWithCredential(credential) .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() { @Override public void onComplete(@NonNull Task<AuthResult> 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(); updateUI(user); } else { // If sign in fails, display a message to the user. Log.w(TAG, "signInWithCredential:failure", task.getException()); Snackbar.make(findViewById(R.id.main_layout), "Authentication Failed.", Snackbar.LENGTH_SHORT).show(); updateUI(null); } // ... } }); }
Kotlin
private fun firebaseAuthWithGoogle(acct: GoogleSignInAccount) { Log.d(TAG, "firebaseAuthWithGoogle:" + acct.id!!) val credential = GoogleAuthProvider.getCredential(acct.idToken, null) auth.signInWithCredential(credential) .addOnCompleteListener(this) { task -> if (task.isSuccessful) { // Sign in success, update UI with the signed-in user's information Log.d(TAG, "signInWithCredential:success") val user = auth.currentUser updateUI(user) } else { // If sign in fails, display a message to the user. Log.w(TAG, "signInWithCredential:failure", task.exception) Snackbar.make(main_layout, "Authentication Failed.", Snackbar.LENGTH_SHORT).show() updateUI(null) } // ... } }
signInWithCredential
succeeds you can use thegetCurrentUser
method to get the user's account data.
Next steps
After a user signs in for the first time, a new user account is created and linked to the credentials—that is, the user name and password, phone number, or auth provider information—the user signed in with. This new account is stored as part of your Firebase project, and can be used to identify a user across every app in your project, regardless of how the user signs in.
-
In your apps, you can get the user's basic profile information from the
FirebaseUser
object. See Manage Users. In your Firebase Realtime Database and Cloud Storage Security Rules, you can get the signed-in user's unique user ID from the
auth
variable, and use it to control what data a user can access.
You can allow users to sign in to your app using multiple authentication providers by linking auth provider credentials to an existing user account.
To sign out a user, call
signOut
:
Java
FirebaseAuth.getInstance().signOut();
Kotlin
FirebaseAuth.getInstance().signOut()