调用：

<component:ImageSwap id="mainImage" width="670" height="100%" preClick="mainImage_preClickHandler(event)"
nextClick="mainImage_nextClickHandler(event)"/>

声明：

实现：

this.dispatchEvent(new Event(‘imageLoaded‘));

dispatchEvent(new MouseEvent("preClick"));

dispatchEvent(new MouseEvent("nextClick"));

flex 自定义事件