You can use Google Play Games services to sign players in to an Android game built on Firebase. To use Google Play Games services sign-in with Firebase, first sign the player in with Google Play Games, and request an OAuth 2.0 auth code when you do so. Then, pass the auth code to `PlayGamesAuthProvider` to generate a Firebase credential, which you can use to authenticate with Firebase. ## Before you begin ### Set up your Android project 1. If you haven't already, [add Firebase to your Android project](https://firebase.google.com/docs/android/setup.md.txt). 2. In your **module (app-level) Gradle file** (usually `//build.gradle.kts` or `//build.gradle`), add the dependency for the Firebase Authentication library for Android. We recommend using the [Firebase Android BoM](https://firebase.google.com/docs/android/learn-more.md.txt#bom) to control library versioning. Also, as part of setting up Firebase Authentication, you need to add the Google Play services SDK to your app. ``` dependencies { // Import the BoM for the Firebase platform implementation(platform("com.google.firebase:firebase-bom:35.1.0")) // Add the dependency for the Firebase Authentication library // When using the BoM, you don't specify versions in Firebase library dependencies implementation("com.google.firebase:firebase-auth") // Also add the dependency for the Google Play services library and specify its version implementation("com.google.android.gms:play-services-auth:22.0.0") } ``` By using the [Firebase Android BoM](https://firebase.google.com/docs/android/learn-more.md.txt#bom), your app will always use compatible versions of Firebase Android libraries. *(Alternative)* Add Firebase library dependencies *without* using the BoM If you choose not to use the Firebase BoM, you must specify each Firebase library version in its dependency line. **Note that if you use *multiple* Firebase libraries in your app, we strongly recommend using the BoM to manage library versions, which ensures that all versions are compatible.** ```groovy dependencies { // Add the dependency for the Firebase Authentication library // When NOT using the BoM, you must specify versions in Firebase library dependencies implementation("com.google.firebase:firebase-auth:25.0.0") // Also add the dependency for the Google Play services library and specify its version implementation("com.google.android.gms:play-services-auth:22.0.0") } ```
### Set up your Firebase project 1. In the Firebase console, go to **Security** \> [**Authentication**](https://console.firebase.google.com/project/_/authentication/). 2. In the **Settings** tab, set your game's SHA-1 fingerprint. You can get the SHA hash of your signing certificate with the gradle `signingReport` command: ``` ./gradlew signingReport ```
3. Enable Google Play Games as a sign-in provider: 1. Find your project's web server client ID and client secret. The web server client ID identifies your Firebase project to the Google Play auth servers. To find these values: 1. Open your Firebase project in the [Google APIs console](https://console.developers.google.com/apis/credentials?project=_) credentials page. 2. In the **OAuth 2.0 client IDs** section, open the **Web client (auto created by Google Service)** details page. This page lists your web server client ID and secret. 2. Back in the Firebase console, go to **Security** \> [**Authentication**](https://console.firebase.google.com/project/_/authentication/). 3. In the **Sign-in method** tab, enable the **Play Games** sign-in provider. You'll need to specify your project's web server client ID and client secret, which you got from the APIs console. ### Configure Play Games services with your Firebase app information 1. In the [Google Play Console](https://play.google.com/console/developers), open your Google Play app or create one. 2. In the *Grow* section, click **Play Games services \> Setup \& Management \> Configuration**. 3. Click **Yes, my game already uses Google APIs** , select your Firebase project from the list, and then click **Use**. 4. On the Play Games services configuration page, click **Add Credential**. 1. Select the **Game server** type. 2. In the **OAuth client** field, select your project's web client ID. Be sure this is the same client ID you specified when you enabled Play Games sign-in. 3. Save your changes. 5. Still on the Play Games services configuration page, click **Add Credential** again. 1. Select the **Android** type. 2. In the **OAuth client** field, select your project's Android client ID. (If you don't see your Android client ID, be sure you set your game's SHA-1 fingerprint in the Firebase console.) 3. Save your changes. 6. On the **Testers** page, add the email addresses of any users who need to be able to sign in to your game before you release it on the Play Store. ## Integrate Play Games sign-in into your game First, integrate Play Games sign-in into your app. See [Sign in to Android Games](https://developers.google.com/games/services/android/signin) for complete instructions. In your integration, when you build the `GoogleSignInOptions` object, use the `DEFAULT_GAMES_SIGN_IN` configuration and call `requestServerAuthCode`: ### Kotlin ```kotlin val gso = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_GAMES_SIGN_IN) .requestServerAuthCode(getString(R.string.default_web_client_id)) .build() ``` ### Java ```java GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_GAMES_SIGN_IN) .requestServerAuthCode(getString(R.string.default_web_client_id)) .build(); ``` You must pass your web server client ID to the `requestServerAuthCode` method. This is the ID that you provided when you enabled Play Games sign-in in the Firebase console. ## Authenticate with Firebase After you add Play Games sign-in to your app, you need to set up Firebase to use the Google Account credentials that you get when a player signs in successfully with Play Games. 1. First, in your sign-in activity's `onCreate` method, get the shared instance of the `FirebaseAuth` object: ### Kotlin ```kotlin private lateinit var auth: FirebaseAuth // ... // Initialize Firebase Auth auth = Firebase.auth ``` ### Java ```java private FirebaseAuth mAuth; // ... // Initialize Firebase Auth mAuth = FirebaseAuth.getInstance(); ``` 2. When initializing your Activity, check to see if the player is already signed in with Firebase: ### Kotlin ```kotlin override fun onStart() { super.onStart() // Check if user is signed in (non-null) and update UI accordingly. val currentUser = auth.currentUser updateUI(currentUser) } ``` ### Java ```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); } ``` If the player isn't signed in, present the player with your game's signed-out experience, including the option to sign in. 3. After a player signs in with Play Games either silently or interactively, get the auth code from the `GoogleSignInAccount` object, exchange it for a Firebase credential, and authenticate with Firebase using the Firebase credential: ### Kotlin ```kotlin // Call this both in the silent sign-in task's OnCompleteListener and in the // Activity's onActivityResult handler. private fun firebaseAuthWithPlayGames(acct: GoogleSignInAccount) { Log.d(TAG, "firebaseAuthWithPlayGames:" + acct.id!!) val auth = Firebase.auth val credential = PlayGamesAuthProvider.getCredential(acct.serverAuthCode!!) 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) Toast.makeText( baseContext, "Authentication failed.", Toast.LENGTH_SHORT, ).show() updateUI(null) } // ... } } ``` ### Java ```java // Call this both in the silent sign-in task's OnCompleteListener and in the // Activity's onActivityResult handler. private void firebaseAuthWithPlayGames(GoogleSignInAccount acct) { Log.d(TAG, "firebaseAuthWithPlayGames:" + acct.getId()); final FirebaseAuth auth = FirebaseAuth.getInstance(); AuthCredential credential = PlayGamesAuthProvider.getCredential(acct.getServerAuthCode()); auth.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 = auth.getCurrentUser(); updateUI(user); } else { // If sign in fails, display a message to the user. Log.w(TAG, "signInWithCredential:failure", task.getException()); Toast.makeText(MainActivity.this, "Authentication failed.", Toast.LENGTH_SHORT).show(); updateUI(null); } // ... } }); } ``` If the call to `signInWithCredential` succeeds you can use the `getCurrentUser` 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 their Play Games ID. 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. In your game, you can get the user's Firebase UID from the `FirebaseUser` object: ### Kotlin ```kotlin val user = auth.currentUser user?.let { val playerName = it.displayName // The user's Id, unique to the Firebase project. // Do NOT use this value to authenticate with your backend server, if you // have one; use FirebaseUser.getIdToken() instead. val uid = it.uid } ``` ### Java ```java FirebaseUser user = mAuth.getCurrentUser(); String playerName = user.getDisplayName(); // The user's Id, unique to the Firebase project. // Do NOT use this value to authenticate with your backend server, if you // have one; use FirebaseUser.getIdToken() instead. String uid = user.getUid(); ``` 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. To get a user's Play Games player information or to access Play Games services, use the APIs provided by the [Google Play Games SDK](https://developers.google.com/games/services/android/quickstart). To sign out a user, call `FirebaseAuth.signOut()`: ### Kotlin ```kotlin Firebase.auth.signOut() ``` ### Java ```java FirebaseAuth.getInstance().signOut(); ```