Authenticate Using Twitter on Android

You can let your users authenticate with Firebase using their Twitter accounts by integrating web-based generic OAuth Login into your app using the Firebase SDK to carry out the end to end sign-in flow.

Before you begin

To sign in users using Twitter accounts, you must first enable Twitter as a sign-in provider for your Firebase project:

If you haven't already, add Firebase to your Android project.
In the Firebase console, open the Auth section.
On the Sign in method tab, enable the Twitter provider.
Add the API key and API secret from that provider's developer console to the provider configuration:
1. Register your app as a developer application on Twitter and get your app's OAuth API key and API secret.
2. Make sure your Firebase OAuth redirect URI (e.g. my-app-12345.firebaseapp.com/__/auth/handler) is set as your Authorization callback URL in your app's settings page on your Twitter app's config.
Click Save.
In your project-level build.gradle file, make sure to include Google's Maven repository in both your buildscript and allprojects sections.
Add the dependency for the Firebase Authentication Android library to your module (app-level) Gradle file (usually app/build.gradle):
```
implementation 'com.google.firebase:firebase-auth:18.1.0'
```
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.

Handle the sign-in flow with the Firebase SDK

If you are building an Android app, the easiest way to authenticate your users with Firebase using their Twitter accounts is to handle the entire sign-in flow with the Firebase Android SDK.

To handle the sign-in flow with the Firebase Android SDK, follow these steps:

Construct an instance of an OAuthProvider using its Builder with the provider ID Twitter.com
```
OAuthProvider.Builder provider = OAuthProvider.newBuilder("twitter.com");
```
Optional: Specify additional custom OAuth parameters that you want to send with the OAuth request.
```
// Target specific email with login hint.
provider.addCustomParameter("lang", "fr");
```
For the parameters Twitter supports, see the Twitter OAuth documentation. Note that you can't pass Firebase-required parameters with setCustomParameters(). These parameters are client_id, response_type, redirect_uri, state, scope and response_mode.

Authenticate with Firebase using the OAuth provider object. Note that unlike other FirebaseAuth operations, this will take control of your UI by popping up a Custom Chrome Tab. As a result, do not reference your Activity in the OnSuccessListener and OnFailureListener that you attach as they will immediately detach when the operation starts the UI.

You should first check if you've already received a response. Signing in via this method puts your Activity in the background, which means that it can be reclaimed by the system during the sign in flow. In order to make sure that you don't make the user try again if this happens, you should check if a result is already present.

To check if there is a pending result, call getPendingAuthResult:

Task<AuthResult> pendingResultTask = firebaseAuth.getPendingAuthResult();
if (pendingResultTask != null) {
  // There's something already here! Finish the sign-in for your user.
  pendingResultTask
      .addOnSuccessListener(
          new OnSuccessListener<AuthResult>() {
            @Override
            public void onSuccess(AuthResult authResult) {
              // User is signed in.
              // IdP data available in
              // authResult.getAdditionalUserInfo().getProfile().
              // The OAuth access token can also be retrieved:
              // authResult.getCredential().getAccessToken().
              // The OAuth secret can be retrieved by calling:
              // authResult.getCredential().getSecret().
            }
          })
      .addOnFailureListener(
          new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
              // Handle failure.
            }
          });
} else {
  // There's no pending result so you need to start the sign-in flow.
  // See below.
}

To start the sign in flow, call startActivityForSignInWithProvider:

firebaseAuth
    .startActivityForSignInWithProvider(/* activity= */ this, provider.build())
    .addOnSuccessListener(
        new OnSuccessListener<AuthResult>() {
          @Override
          public void onSuccess(AuthResult authResult) {
            // User is signed in.
            // IdP data available in
            // authResult.getAdditionalUserInfo().getProfile().
            // The OAuth access token can also be retrieved:
            // authResult.getCredential().getAccessToken().
            // The OAuth secret can be retrieved by calling:
            // authResult.getCredential().getSecret().
          }
        })
    .addOnFailureListener(
        new OnFailureListener() {
          @Override
          public void onFailure(@NonNull Exception e) {
            // Handle failure.
          }
        });

On successful completion, the OAuth access token associated with the provider can be retrieved from the OAuthCredential object returned.

Using the OAuth access token, you can call the Twitter API.

For example, to get basic profile information, you can call the REST API, passing the access token in the Authorization header:

While the above examples focus on sign-in flows, you also have the ability to link a Twitter provider to an existing user using startActivityForLinkWithProvider. For example, you can link multiple providers to the same user allowing them to sign in with either.

// The user is already signed-in.
FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();

firebaseUser
    .startActivityForLinkWithProvider(/* activity= */ this, provider.build())
    .addOnSuccessListener(
        new OnSuccessListener<AuthResult>() {
          @Override
          public void onSuccess(AuthResult authResult) {
            // Twitter credential is linked to the current user.
            // IdP data available in
            // authResult.getAdditionalUserInfo().getProfile().
            // The OAuth access token can also be retrieved:
            // authResult.getCredential().getAccessToken().
            // The OAuth secret can be retrieved by calling:
            // authResult.getCredential().getSecret().
          }
        })
    .addOnFailureListener(
        new OnFailureListener() {
          @Override
          public void onFailure(@NonNull Exception e) {
            // Handle failure.
          }
        });

The same pattern can be used with startActivityForReauthenticateWithProvider which can be used to retrieve fresh credentials for sensitive operations that require recent login.

// The user is already signed-in.
FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();

firebaseUser
    .startActivityForReauthenticateWithProvider(/* activity= */ this, provider.build())
    .addOnSuccessListener(
        new OnSuccessListener<AuthResult>() {
          @Override
          public void onSuccess(AuthResult authResult) {
            // User is re-authenticated with fresh tokens and
            // should be able to perform sensitive operations
            // like account deletion and email or password
            // update.
          }
        })
    .addOnFailureListener(
        new OnFailureListener() {
          @Override
          public void onFailure(@NonNull Exception e) {
            // Handle failure.
          }
        });

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();MainActivity.java

Kotlin

FirebaseAuth.getInstance().signOut()MainActivity.kt