This Android project a sample of using Facebook Account Kit with Firebase Authentication for this tutorial.
You should set Cloud Functions Endpoint in the app/build.gradle
buildConfigField "String", "CLOUD_FUNCTIONS_ENDPOINT", '"<PUT YOUR ENDPOINT HERE>"'
and add two string values:
<string name="facebook_app_id">FACEBOOK_APP_ID</string>
<string name="account_kit_client_token">FACEBOOK_ACCOUNT_KIT_CLIENT_TOKEN</string>
and of course you should connect the project to Firebase.