A stub app showing how to access Google Photos (or any other Google API) from Android. This app uses your apps signature instead of a secret to authenticate. It requires more setup, but it's considerably less code. I believe it's more secure as well.

• You'll need find your keystore.debug. You can Google to find it's location for your OS. For me it was in ~/.android/debug.keystore. I like to copy it into a directly parallel to may app do I don't check it in.
• Setup your app in Firebase.
  • https://console.firebase.google.com/
• You'll need to enable the Photos API
  • https://developers.google.com/photos/library/guides/get-started-java
• You'll need to create "OAuth 2.0 Client IDs" for your app's debug and, eventually, it's release signature to authenticate without a secret.
  • Head to https://console.cloud.google.com/apis/credentials
  • Hit "+CREATE CREDENTIALS"
  • Follow the prompts
• While you are in the Cloud Console, setup the OAuth consent screen.
  • This is where you set your OAuth scopes (see Photos API for a complete list). I would start with read only.
  • Since this is a test app, you'll need to add some users.
• Go into Firebase and generate your google-services.json. Put it in the "app" root as described A little Google magic here. Your OAuth 2.0 Client ID gets added!
  • https://support.google.com/firebase/answer/7015592
  • Make sure you add a support email while you are at it, some people have had issues if you don't.

Like all OAuth tokens, the token returned from GoogleAuthUtil.getToken() will eventually need to be refreshed. Since I'm using a GoogleCredentials class it may happen automatically, but most likely you'll have to call GoogleAuthUtil.getToken() again.