Flex 初始化时的事件测试,这样初始化顺序就很明显,细致了。

flex组件在建立的时候都会经历四个事件：preinitialize, initialize, creationComplete和updateComplete（updateComplete事件在任何改动视觉的情况下都会发生，不是初始化时独有的）。我这里有个例子来检测在嵌套和平行的情况下，测试各个组件的事件抛出顺序。

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"
preinitialize="showEvent(event)"
initialize="showEvent(event)"
creationComplete="showEvent(event)"
updateComplete="showEvent(event)">

<mx:Script>
<!--[CDATA[
import flash.utils.getTimer;
private function showEvent(event:Event):void
{
trace(flash.utils.getTimer().toString()+" >> "
+event.currentTarget.name+" "+event.type);
}
]]-->
</mx:Script>

<mx:Canvas id="canv1"
preinitialize="showEvent(event)"
initialize="showEvent(event)"
creationComplete="showEvent(event)"
updateComplete="showEvent(event)">

<mx:Button id="btn1"
preinitialize="showEvent(event)"
initialize="showEvent(event)"
creationComplete="showEvent(event)"
updateComplete="showEvent(event)"/>
</mx:Canvas>

<mx:Button id="btn2"
preinitialize="showEvent(event)"
initialize="showEvent(event)"
creationComplete="showEvent(event)"
updateComplete="showEvent(event)"/>

</mx:Application>

输出：

349 >> InitExample0 preinitialize
356 >> canv1 preinitialize
359 >> btn1 preinitialize
369 >> btn1 initialize
370 >> canv1 initialize
371 >> btn2 preinitialize
372 >> btn2 initialize
372 >> InitExample0 initialize
476 >> btn1 creationComplete
477 >> btn1 updateComplete
477 >> canv1 creationComplete
477 >> canv1 updateComplete
477 >> btn2 creationComplete
477 >> btn2 updateComplete
478 >> InitExample0 creationComplete
481 >> InitExample0 updateComplete

结论：

就单个组件而言，事件的抛出顺序是preinitialize，initialize，creationComplete


嵌套关系的两个组件（比如Canvas和button1），preinitialize先外后内，initialize和creationComplete先内后外。只是creationComplete要在下一次update才会发生。

平行关系的两个组件（比如Canvas和button2），按mxml内的顺序，只有前面组件initialize结束后，后面的组件才会抛出preinitialize。