E4/Modeled UI 监听模型修改[译]

    当模型发生变化(比如只是更改标签组件的Text属性)时，会将事件给通知注册的事件处理器。在E4中使用了全局的事件模式,处理订阅的事件。

   订阅模型修改事件

    通过UIEvents类生成订阅事件的主题，

// subscribe to all events generated from MUILabels
eventBroker.subscribe(UIEvents.buildTopic(UIEvents.UILabel.TOPIC),labelEventHandler);
 
// subscribe only to events generated from MItems's selected attribute being switched
eventBroker.subscribe(UIEvents.buildTopic(UIEvents.Item.TOPIC, UIEvents,Item.SELECTED),itemSelectionEventHandler);

      处理事件信息

// subscribe to events generated from MUILabels having their labels changed
eventBroker.subscribe(UIEvents.buildTopic(UIEvents.UILabel.TOPIC, UIEvents.UILabel.LABEL),
    new EventHandler() {
      public void handleEvent(Event event) {
        Object element = event.getProperty(UIEvents.EventTags.ELEMENT);
        if (element instanceof MToolItem) {
          ToolItem item = (ToolItem) ((MToolItem) element).getWidget();
          String value = (String) event.getProperty(UIEvents.EventTags.NEW_VALUE);
          if (value == null) {
            item.setText(""); //$NON-NLS-1$
          } else {
            item.setText(value);
          }
        }
      }
    }
);

原文:http://wiki.eclipse.org/Eclipse4/RCP/Modeled_UI/Listening_to_Model_Changes