flex的stage

现在我们先看看代码,下面的代码装在creationComplete事件中调用init()来启动全屏.

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1. <?xml version="1.0" encoding="utf-8"?>   
2. <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"    
3.     layout="absolute"  
4.     creationComplete="init()"  
5.     >   
6.     <mx:Script>   
7.         <![CDATA[   
8.             private function init():void{   
9.                 stage.displayState = StageDisplayState.FULL_SCREEN;    
10.             }   
11.         ]]>   
12.     </mx:Script>   
13. </mx:Application>  

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="absolute"
creationComplete="init()"
>
<mx:Script>
<![CDATA[
private function init():void{
stage.displayState = StageDisplayState.FULL_SCREEN;
}
]]>
</mx:Script>
</mx:Application>

现在保存运行一下swf,却有TypeError..详细信息如下

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1. Main Thread (Suspended: TypeError: Error #1009: 无法访问空对象引用的属性或方法。)     
2.     swf_fullscreen/init     
3.     swf_fullscreen/___swf_fullscreen_Application1_creationComplete     
4.     flash.events::EventDispatcher/dispatchEventFunction [no source]     
5.     flash.events::EventDispatcher/dispatchEvent [no source]     
6.     mx.core::UIComponent/dispatchEvent     
7.     mx.core::UIComponent/set initialized     
8.     mx.managers::LayoutManager/doPhasedInstantiation     
9.     Function/http://adobe.com/AS3/2006/builtin::apply [no source]     
10.     mx.core::UIComponent/callLaterDispatcher2     
11.     mx.core::UIComponent/callLaterDispatcher    

Main Thread (Suspended: TypeError: Error #1009: 无法访问空对象引用的属性或方法。)  
swf_fullscreen/init  
swf_fullscreen/___swf_fullscreen_Application1_creationComplete  
flash.events::EventDispatcher/dispatchEventFunction [no source]  
flash.events::EventDispatcher/dispatchEvent [no source]  
mx.core::UIComponent/dispatchEvent  
mx.core::UIComponent/set initialized  
mx.managers::LayoutManager/doPhasedInstantiation  
Function/http://adobe.com/AS3/2006/builtin::apply [no source]  
mx.core::UIComponent/callLaterDispatcher2  
mx.core::UIComponent/callLaterDispatcher  

我们把init()修改一下,如果

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1. private function init():void{   
2.     trace(stage)   
3. }  

private function init():void{
trace(stage)
}

运行保存运行swf,发现输入null,奇怪的事情发生了..stage竟然为null,那进行stage.displayState当然就报错了...
再次修改程序,使用click调用init(),stage正常输出,那问题大概就是creationComplete调用时,stage初始化..

后来网上查了一下..发现了一个叫callLater的函数,他的功能大概是..进入下一帧的时候,执行函数,我们再次修改代码:

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1. <?xml version="1.0" encoding="utf-8"?>   
2. <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"    
3.     layout="absolute"  
4.     creationComplete="callLater(init)"  
5.     >   
6.     <mx:Script>   
7.         <![CDATA[   
8.             private function init():void{   
9.                 stage.displayState = StageDisplayState.FULL_SCREEN;    
10.             }   
11.         ]]>   
12.     </mx:Script>   
13. </mx:Application>  

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="absolute"
creationComplete="callLater(init)"
>
<mx:Script>
<![CDATA[
private function init():void{
stage.displayState = StageDisplayState.FULL_SCREEN;
}
]]>
</mx:Script>
</mx:Application>

我们在creationComplete事件里,使用callLater(init)来调用init,让init在进入下一侦的时候再全屏..
保存运行swf,问题解决....

ps:另外swf还可以使用fscommand("fullscreen", "true");来进行全屏..这里只是主要讨论stage为null的问题.