code: @UiHandler("navTree")
    final void menuItemSelected(final SelectionEvent<TreeItem> pselectionEvent) {
      if (selectedItem != null && !selectedItem.equals(pselectionEvent.getSelectedItem())) {
        // workaround, revert selection, it's triggered by the selected page
        pselectionEvent.getSelectedItem().setSelected(false);
        selectedItem.setSelected(true);
      }
    }
docs: menu item is selected in the menu tree.
  
  @param pselectionEvent selection event.