code: public final void onCreate(@NonNull final Object client,
              @Nullable final Bundle savedInstanceState) {
          mGUIClient = client;
          if (savedInstanceState != null) {
              mChronosListener = ChronosListenerManager.getInstance()
                      .getListener(savedInstanceState.getInt(KEY_CHRONOS_LISTENER_ID));
          } else {
              mChronosListener = ChronosListenerManager.getInstance()
                      .createListener();
          }
      }
docs: GUI client should call this method in its own onCreate() method.
  
  @param client             a client that holds the helper
  @param savedInstanceState parameter from the corresponding client method