Signing in users with Apple on Android

This document shows you how to use Identity Platform to add Sign in with Apple to your Android app.

Before you begin

Create an Android app that uses Identity Platform.
Join the Apple Developer Program.

Configuring your app with Apple

On the Apple Developer site:

Follow the steps in Configure Sign in with Apple for the web. This includes:
1. Registering a Return URL, which looks like:
```
https://project-id.firebaseapp.com/__/auth/handler
```
2. Temporarily hosting a file at the following URL to verify your domain:
```
https://project-id.firebaseapp.com/.well-known/apple-developer-domain-association.txt
```
Additionally, take note of your Services ID and Apple team ID — you'll need them in the next section.
Use an Apple private key to create a sign in. You'll need the key and its ID in the next section.
If you use Identity Platform to send emails to your users, configure your project with Apple's private email relay service using the following email:
```
noreply@project-id.firebaseapp.com
```
You can also use a custom email template, if your app has one.

Complying with Apple's anonymized data requirements

Apple gives users the option of anonymizing their data, including their email address. Apple assigns users who select this option an obfuscated email address with the domain privaterelay.appleid.com.

Your app must comply with any applicable developer policies or terms from Apple regarding anonymized Apple IDs. This includes obtaining user consent before associating any personally identifying information (PII) with an anonymized Apple ID. Actions that involve PII include, but are not limited to:

Linking an email address to an anonymized Apple ID, or vice versa.
Linking a phone number to an anonymized Apple ID, or vice versa
Linking a non-anonymous social credential, such as Facebook or Google, to to anonymized Apple ID, or vice versa.

For more information, refer to the Apple Developer Program License Agreement for your Apple developer account.

Configuring Apple as a provider

To configure Apple as an identity provider:

Go to the Identity Providers page in the Google Cloud console.

Go to the Identity Providers page
Click Add a Provider.
Select Apple from the list.
Under Platform, select Android.
Enter your Services ID, Apple team ID, Key ID, and Private key.
Register your app's domains by clicking Add domain under Authorized domains. For development purposes, localhost is already enabled by default.
Under Configure your application, click Android. Copy the snippet into your app's code to initialize the Identity Platform client SDK.
Click Save.

Signing in users with the client SDK

Create an instance of the OAuthProvider provider object, using the ID apple.com:

Java

OAuthProvider.Builder provider = OAuthProvider.newBuilder("apple.com");

Kotlin

val provider = OAuthProvider.newBuilder("apple.com")

Optional: Add OAuth scopes. Scopes specify what data you are requesting from Apple. More sensitive data may require specific scopes. By default, when One account per email address is enabled, Identity Platform requests the email and name scopes.
Java
```
List<String> scopes =
    new ArrayList<String>() {
      {
        add("email");
        add("name");
      }
    };
provider.setScopes(scopes);
```
Kotlin
```
provider.setScopes(arrayOf("email", "name"))
```

Optional: Localize the authentication flow. You can specify a language, or use the device's default language:

Java

// Localize the Apple authentication screen in French.
provider.addCustomParameter("locale", "fr");

Kotlin

// Localize the Apple authentication screen in French.
provider.addCustomParameter("locale", "fr");

Check if a response is already present by calling startActivityForSignInWithProvider():

Java

mAuth = FirebaseAuth.getInstance();
Task<AuthResult> pending = mAuth.getPendingAuthResult();
if (pending != null) {
    pending.addOnSuccessListener(new OnSuccessListener<AuthResult>() {
        @Override
        public void onSuccess(AuthResult authResult) {
            Log.d(TAG, "checkPending:onSuccess:" + authResult);
            // Get the user profile with authResult.getUser() and
            // authResult.getAdditionalUserInfo(), and the ID
            // token from Apple with authResult.getCredential().
        }
    }).addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            Log.w(TAG, "checkPending:onFailure", e);
        }
    });
} else {
    Log.d(TAG, "pending: null");
}

Kotlin

val pending = auth.pendingAuthResult
if (pending != null) {
    pending.addOnSuccessListener { authResult ->
        Log.d(TAG, "checkPending:onSuccess:$authResult")
        // Get the user profile with authResult.getUser() and
        // authResult.getAdditionalUserInfo(), and the ID
        // token from Apple with authResult.getCredential().
    }.addOnFailureListener { e ->
        Log.w(TAG, "checkPending:onFailure", e)
    }
} else {
    Log.d(TAG, "pending: null")
}

Signing in puts your Activity in the background, which means the system can reclaim it during the authentication flow. Checking if a result is already present prevents the user from having to sign in twice.

If there's no pending result, call startActivityForSignInWithProvider():

Java

mAuth.startActivityForSignInWithProvider(this, provider.build())
    .addOnSuccessListener(
            new OnSuccessListener<AuthResult>() {
                @Override
                public void onSuccess(AuthResult authResult) {
                    // Sign-in successful!
                    Log.d(TAG, "activitySignIn:onSuccess:" + authResult.getUser());
                    FirebaseUser user = authResult.getUser();
                    // ...
                }
            })
    .addOnFailureListener(
            new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    Log.w(TAG, "activitySignIn:onFailure", e);
                }
            });

Kotlin

auth.startActivityForSignInWithProvider(this, provider.build())
  .addOnSuccessListener { authResult ->
      // Sign-in successful!
      Log.d(TAG, "activitySignIn:onSuccess:${authResult.user}")
      val user = authResult.user
      // ...
  }
  .addOnFailureListener { e ->
      Log.w(TAG, "activitySignIn:onFailure", e)
  }

Unlike many other identity providers, Apple does not provide a photo URL.

If a user chooses not to share their real email with your app, Apple provisions a unique email address for that user to share instead. This email takes the form [email protected]. If you configured the private email relay service, Apple forwards emails sent to the anonymized address to the user's real email address.

Apple only shares user information, such as display names, with apps the first time a user signs in. In most cases, Identity Platform stores this data, which lets you fetch it using firebase.auth().currentUser.displayName during future sessions. However, if you allowed users to sign into your app using Apple before integrating with Identity Platform, user information is not available.

What's next

Learn more about Identity Platform users.
Sign in users with other identity providers.