Products Google APIs for Android Reference GoogleSignInOptionsExtension public interface GoogleSignInOptionsExtension An interface for API specific extension for GoogleSignInOptions. See also addExtension(GoogleSignInOptionsExtension). Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see our Site Policies. Java is a registered trademark of Oracle and/or its affiliates. Last updated August 7, 2019.