我创建了2个lists called list1 and list2 and the list elements inside it are draggable to a树. But I need to validate in such a way that only after dragging one element in list1，然后可以将任意数量的list2元素拖到{{1}的子树中}}
tab_folder1那么请问我们如何在SWT中验证list2元素应该始终是list1的子元素？