code: private void noInteractionCheckAuthentication(AuthorizationResponse response)
      {
          // If the current user has already been authenticated.
          if (mSpi.isUserAuthenticated())
          {
              // OK.
              return;
          }
  
          // A user must have logged in.
          throw getApiCaller().authorizationFail(response.getTicket(), Reason.NOT_LOGGED_IN);
      }
docs: Check whether an end-user has already logged in or not.