FLEX的初始化顺序

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)。

 

下面的例子检测在嵌套和平行的情况下,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>

 

 

 

上面的例子输出顺序是:

1299 >> eventTest0 preinitialize

1307 >> canv1 preinitialize

1310 >> btn1 preinitialize

1318 >> btn1 initialize

1319 >> canv1 initialize

1320 >> btn2 preinitialize

1321 >> btn2 initialize

1321 >> eventTest0 initialize

[SWF] G:/projects/eventTest/bin-debug/eventTest.swf - 588,818 bytes after decompression

1387 >> btn1 creationComplete

1387 >> btn1 updateComplete

1387 >> canv1 creationComplete

1387 >> canv1 updateComplete

1388 >> btn2 creationComplete

1388 >> btn2 updateComplete

1388 >> eventTest0 creationComplete

1390 >> eventTest0 updateComplete

 

看着有点混乱,不过仔细看看,可以把过程分成两个部分。

很明显,所有的creationComplete和updateComplete发生在第二次update的时候,之前flex组件只是做一些设置和计算的工作,并没有在画布上画任何东西。除此之外,还有这么一些规律:

  • 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。

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