gsi.java

if (opr.isDone()) {
  // If the user's cached credentials are valid, the OptionalPendingResult will be "done"
  // and the GoogleSignInResult will be available instantly. We can try and retrieve an
  // authentication code.
  GoogleSignInResult result = opr.get();
  handleSignInResult(result);
} else {
  // If the user has not previously signed in on this device or the sign-in has expired,
  // this asynchronous branch will attempt to sign in the user silently.
  opr.setResultCallback(new ResultCallback<GoogleSignInResult>() {
      @Override
      public void onResult(@NonNull GoogleSignInResult googleSignInResult) {
          handleSignInResult(googleSignInResult);
      }
  });
}