viewer.addDoubleClickListener(new IDoubleClickListener() {
		    	
  @Override
   public void doubleClick(DoubleClickEvent event) {
	TreeViewer viewer = (TreeViewer) event.getViewer();
	IStructuredSelection thisSelection = (IStructuredSelection) event
		            .getSelection();
		        
	 Object selectedNode = thisSelection.getFirstElement();
	  
           //TODO somthing with selectedNode 
		        
		        
		        
		       
		        
		      }
		    });

if (selectedNode instanceof NavigatorMenuItem) {
      NavigatorMenuItem o = (NavigatorMenuItem) selectedNode;
		        
       System.out.println(o.getItemLibelle()) ;  	   
		        	   
		         
		        }