将上下文菜单附加到GWT MenuItem

Question

GWT MenuItem扩展了UIObject - 任何想法如何添加事件处理程序，例如我想要一个特殊的上下文菜单来右键单击MenuItem。谢谢！

Answer 1

您可以使用MenuItem对象的底层元素：

final Element element = menuItem.getElement();
Event.addNativePreviewHandler(new Event.NativePreviewHandler() {
    @Override
    public void onPreviewNativeEvent(Event.NativePreviewEvent event) {
        if (event.getTypeInt() == Event.ONMOUSEDOWN 
                && event.getNativeEvent().getButton() == Event.BUTTON_RIGHT 
                && event.getNativeEvent().getEventTarget().equals(element)) {
            showSpecialMenu();
        }
    }
});

Event.sinkEvents(element, Event.ONMOUSEDOWN);

或者像这样（你也可以阻止默认的上下文菜单）：

final Element element = menuItem.getElement();
Event.addNativePreviewHandler(new Event.NativePreviewHandler() {
    @Override
    public void onPreviewNativeEvent(Event.NativePreviewEvent event) {
        if (event.getTypeInt() == Event.ONCONTEXTMENU && event.getNativeEvent().getEventTarget().equals(element)) {
            // prevent default context menu
            event.getNativeEvent().stopPropagation();
            event.getNativeEvent().preventDefault();

            // show custom context menu
            showSpecialMenu();
        }
    }
});

Event.sinkEvents(element, Event.ONCONTEXTMENU);

你可以这样做：

......
Event.sinkEvents(element, Event.ONCONTEXTMENU | Event.ONMOUSEDOWN);