Authenticate Using Facebook Login on Android

You can let your users authenticate with Firebase using their Facebook accounts by integrating Facebook Login into your app.

Before you begin

1. Add Firebase to your Android project.
2. If you haven't yet connected your app to your Firebase project, do so from the Firebase console.
3. Add the dependency for Firebase Authentication to your app-level build.gradle file:

   compile 'com.google.firebase:firebase-auth:10.0.1'

4. On the Facebook for Developers site, get the App ID and an App Secret for your app.
5. Enable Facebook Login:
   1. In the Firebase console, open the Auth section.
   2. On the Sign in method tab, enable the Facebook sign-in method and specify the App ID and App Secret you got from Facebook.
   3. Then, make sure your OAuth redirect URI (e.g. 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 in the Product Settings > Facebook Login config.

Authenticate with Firebase

1. Integrate Facebook Login into your app by following the developer's documentation. 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:

   // Initialize Facebook Login button
   mCallbackManager = CallbackManager.Factory.create();
   LoginButton loginButton = (LoginButton) findViewById(R.id.button_facebook_login);
   loginButton.setReadPermissions("email", "public_profile");
   loginButton.registerCallback(mCallbackManager, new FacebookCallback<LoginResult>() {
       @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);
   }
   FacebookLoginActivity.java
   

2. In your sign-in activity's onCreate method, get the shared instance of the FirebaseAuth object:

   private FirebaseAuth mAuth;
   // ...
   // Initialize Firebase Auth
   mAuth = FirebaseAuth.getInstance();
   FacebookLoginActivity.java
   

3. Set up an AuthStateListener that responds to changes in the user's sign-in state:

   private FirebaseAuth.AuthStateListener mAuthListener;
   
   // ...
   
   @Override
   protected void onCreate(Bundle savedInstanceState) {
       // ...
       mAuthListener = new FirebaseAuth.AuthStateListener() {
           @Override
           public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
               FirebaseUser user = firebaseAuth.getCurrentUser();
               if (user != null) {
                   // User is signed in
                   Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
               } else {
                   // User is signed out
                   Log.d(TAG, "onAuthStateChanged:signed_out");
               }
               // ...
           }
       };
       // ...
   }
   
   @Override
   public void onStart() {
       super.onStart();
       mAuth.addAuthStateListener(mAuthListener);
   }
   
   @Override
   public void onStop() {
       super.onStop();
       if (mAuthListener != null) {
           mAuth.removeAuthStateListener(mAuthListener);
       }
   }
   FacebookLoginActivity.java
   

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:

   private void handleFacebookAccessToken(AccessToken token) {
       Log.d(TAG, "handleFacebookAccessToken:" + token);
   
       AuthCredential credential = FacebookAuthProvider.getCredential(token.getToken());
       mAuth.signInWithCredential(credential)
               .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                   @Override
                   public void onComplete(@NonNull Task<AuthResult> task) {
                       Log.d(TAG, "signInWithCredential:onComplete:" + task.isSuccessful());
   
                       // If sign in fails, display a message to the user. If sign in succeeds
                       // the auth state listener will be notified and logic to handle the
                       // signed in user can be handled in the listener.
                       if (!task.isSuccessful()) {
                           Log.w(TAG, "signInWithCredential", task.getException());
                           Toast.makeText(FacebookLoginActivity.this, "Authentication failed.",
                                   Toast.LENGTH_SHORT).show();
                       }
   
                       // ...
                   }
               });
   }
   FacebookLoginActivity.java
   

   If the call to signInWithCredential succeeds, the AuthStateListener runs the onAuthStateChanged callback. In the callback, 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, 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 Firebase 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:

FirebaseAuth.getInstance().signOut();