RequestToken.java

//Request google sign in
Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
startActivityForResult(signInIntent, RC_SIGN_IN);

//Get selected account data
@Override
  public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == RC_SIGN_IN) {
      GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
      GoogleSignInAccount acct = result.getSignInAccount();
      //TOKEN
      String token = acct.getIdToken();
    }
}