You can let your users authenticate with Firebase using their Facebook accounts by integrating Facebook Login into your app. ## Before you begin 1. If you haven't already, [add Firebase to your Android project](https://firebase.google.com/docs/android/setup.md.txt). 2. In the [Facebook for Developers site](https://developers.facebook.com/), get the **App ID** and an **App Secret** for your app. 3. Enable Facebook Login as a sign-in provider for your Firebase project: 1. In the Firebase console, go to **Security** \> [**Authentication**](https://console.firebase.google.com/project/_/authentication/). 2. In the **Sign-in method** tab, enable the **Facebook** sign-in provider, and specify the **App ID** and **App Secret** you got from Facebook. 3. Make sure your **OAuth redirect URI** (for example, `my-app-12345.firebaseapp.com/__/auth/handler`) is listed as one of your **OAuth redirect URIs** in your Facebook app's settings page on the [Facebook for Developers site](https://developers.facebook.com/) in the **Product Settings \> Facebook Login** config. 4. 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. ``` 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") } ``` 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") } ```
## Authenticate with Firebase 1. Integrate Facebook Login into your app by following the [developer's documentation](https://developers.facebook.com/docs/facebook-login/android). When you configure the `LoginButton` or `LoginManager` object, request the `public_profile` and `email` permissions. If you integrated Facebook Login using a `LoginButton`, your sign-in activity has code similar to the following: ### Kotlin ```kotlin // Initialize Facebook Login button callbackManager = CallbackManager.Factory.create() buttonFacebookLogin.setReadPermissions("email", "public_profile") buttonFacebookLogin.registerCallback( callbackManager, object : FacebookCallback { override fun onSuccess(loginResult: LoginResult) { Log.d(TAG, "facebook:onSuccess:$loginResult") handleFacebookAccessToken(loginResult.accessToken) } override fun onCancel() { Log.d(TAG, "facebook:onCancel") } override fun onError(error: FacebookException) { Log.d(TAG, "facebook:onError", error) } }, ) // ... override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) { super.onActivityResult(requestCode, resultCode, data) // Pass the activity result back to the Facebook SDK callbackManager.onActivityResult(requestCode, resultCode, data) } ``` ### Java ```java // Initialize Facebook Login button mCallbackManager = CallbackManager.Factory.create(); LoginButton loginButton = findViewById(R.id.button_sign_in); loginButton.setReadPermissions("email", "public_profile"); loginButton.registerCallback(mCallbackManager, new FacebookCallback() { @Override public void onSuccess(LoginResult loginResult) { Log.d(TAG, "facebook:onSuccess:" + loginResult); handleFacebookAccessToken(loginResult.getAccessToken()); } @Override public void onCancel() { Log.d(TAG, "facebook:onCancel"); } @Override public void onError(FacebookException error) { Log.d(TAG, "facebook:onError", error); } }); // ... @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); // Pass the activity result back to the Facebook SDK mCallbackManager.onActivityResult(requestCode, resultCode, data); } ``` 2. 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(); ``` 3. When initializing your Activity, check to see if the user is currently signed in: ### Kotlin ```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) } ``` ### 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); } ``` 4. After a user successfully signs in, in the `LoginButton`'s `onSuccess` callback method, get an access token for the signed-in user, exchange it for a Firebase credential, and authenticate with Firebase using the Firebase credential: ### Kotlin ```kotlin private fun handleFacebookAccessToken(token: AccessToken) { Log.d(TAG, "handleFacebookAccessToken:$token") val credential = FacebookAuthProvider.getCredential(token.token) 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 private void handleFacebookAccessToken(AccessToken token) { Log.d(TAG, "handleFacebookAccessToken:" + token); AuthCredential credential = FacebookAuthProvider.getCredential(token.getToken()); mAuth.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(); updateUI(user); } else { // If sign in fails, display a message to the user. Log.w(TAG, "signInWithCredential:failure", task.getException()); Toast.makeText(FacebookLoginActivity.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 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`](https://firebase.google.com/docs/reference/android/com/google/firebase/auth/FirebaseUser.md.txt) object. See [Manage Users](https://firebase.google.com/docs/auth/android/manage-users.md.txt). - In your Firebase Realtime Database and Cloud Storage [Security Rules](https://firebase.google.com/docs/database/security/user-security), 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.](https://firebase.google.com/docs/auth/android/account-linking) To sign out a user, call [`signOut`](https://firebase.google.com/docs/reference/android/com/google/firebase/auth/FirebaseAuth.md.txt#signOut()): ### Kotlin ```kotlin Firebase.auth.signOut() ``` ### Java ```java FirebaseAuth.getInstance().signOut(); ```