I have an application in the game and would like to leave it more attractive using gamefication. I researched and found the Google Play Game Service with your Leaderboard and Achievements, which would be ideal for me.
In my app the user must be logged in, so it was already implemented two options for login: through the facebook button and Google Sign In API (using com.google.android.gms.common.SignInButton in xml). Now I decided to implement Google Play Game Service, seen in the documentation that it has a deployment login.
So my big question is, how should I act as the user can log in by Google or Facebook? I need to replace the implementation of Google Sign In API from Google Play Game Service? An alternative approach?
Thank you all