code: public void showProgress(boolean show) {
          if (actionButton != null) {
              actionButton.showProgress(show);
          }
          if (formLayout != null) {
              formLayout.setEnabled(!show);
          }
      }
docs: Displays a progress bar on top of the action button. This will also
  enable or disable the action button.
  
  @param show whether to show or hide the action bar.