这里把去点击某个小部件(widget)所导致的事件的过程当作是被动的。因为事件触发是被动的。
主动是指在其它部分的代码里去触发小部件所注册的事件，而本身并没有真正意义上的去点击控件。
使用示例
Event event = new Event();
event.type = SWT.Selection;
b1.notifyListeners(SWT.Selection, event);
方法描述和原型：
/**
* Notifies all of the receiver's listeners for events
* of the given type that one such event has occurred by
* invoking their <code>handleEvent()</code> method. The
* event type is one of the event constants defined in class
* <code>SWT</code>.
*
* @param eventType the type of event which has occurred
* @param event the event data
*
* @exception SWTException <ul>
* <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
* <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
* </ul>
*
* @see SWT
* @see #addListener
* @see #getListeners(int)
* @see #removeListener(int, Listener)
*/
public void notifyListeners (int eventType, Event event) {
checkWidget();
if (event == null) event = new Event ();
sendEvent (eventType, event);
}