code: @Override
      public void onClick()
      {
          Instance instance = null;
          final AbstractUIField uiField = super.getModelObject();
          if (uiField.getInstanceKey() != null) {
              Menu menu = null;
              try {
                  instance = uiField.getInstance();
                  menu = Menu.getTypeTreeMenu(instance.getType());
              } catch (final EFapsException e) {
                  throw new RestartResponseException(new ErrorPage(e));
              }
              if (menu == null) {
                  final Exception ex = new Exception("no tree menu defined for type " + instance.getType().getName());
                  throw new RestartResponseException(new ErrorPage(ex));
              }
  
              Page page;
              try {
                  page = new ContentContainerPage(menu.getUUID(), uiField.getInstanceKey(),
                                  getPage() instanceof StructurBrowserPage);
              } catch (final EFapsException e) {
                  page = new ErrorPage(e);
              }
              this.setResponsePage(page);
          }
      }
docs: Method is executed on click.