How to control whether the action in the eclipse view is displayed (or available)

During Eclipse plug-in development, we sometimes have the following requirement: we need to add popupmeun to the view. If we want only the corresponding action of the leaf node,

 

 

 

Instead of leaf nodes or empty rows, the system does not respond to the action. For example, the following figure does not show:

 

 

You can rewritefillContextMenu(ImenumanagerMenu) method, simplified code:

 

public void fillContextMenu(final IMenuManager menu) {final MenuManager menuManager = (MenuManager) menu;menu.setRemoveAllWhenShown(true);menu.addMenuListener(new IMenuListener(){public void menuAboutToShow(IMenuManager manager) {if(){//if the select item is empty.do nothing              }else{//if the select item isn't ScanPatternEntity,availablemenuManager.add(new NewExpainAction());}}});}