AS3跨域加载图片时设置LoaderContext类

今天碰到的小问题，AS2加载外部图片从来没这么麻烦过...OK，认了。跨域加载外部图片除需要设置crossdomain外，还需要在loader.load()方法添加context参数，文档显示context参数为LoaderContext 类：

load(request:URLRequest, context:LoaderContext = null):void

When loading images (JPEG, GIF, or PNG) instead of SWF files, there is no need to specify a SecurityDomain or an application domain, because those concepts are meaningful only for SWF files. Instead, you have only one decision to make: do you need programmatic access to the pixels of the loaded image? If so, see the checkPolicyFile property.
所以，跨域加载正确的写法为：


import flash.system.LoaderContext;

var lc:LoaderContext = new LoaderContext(true);
var loader:Loader = new Loader();
var request:URLRequest = new URLRequest(url);
loader.load(request, lc);


否则，flash player安全沙箱会报“checkPolicyFile ”错误。

这个疏忽出现在了Papervision3D中。使用BitmapFileMaterial时，如果使用的是跨域图片进行贴图，尽管设置了crossdomain.xml，仍然会报沙箱错误，解决方法是修改loadNextBitmap方法：


// ___________________________________________________________________ LOAD NEXT BITMAP

private function loadNextBitmap():void
{
// Retrieve next filename in queue
var file:String = _waitingBitmaps[0];

var request:URLRequest = new URLRequest( file );
var lc:LoaderContext = new LoaderContext(true);
var bitmapLoader:Loader = new Loader();

bitmapLoader.contentLoaderInfo.addEventListener( Event.COMPLETE, loadBitmapCompleteHandler );

try
{
// Load bitmap
bitmapLoader.load( request, lc );

// Save original url
_loaderUrls[ bitmapLoader ] = file;

// Busy loading
_loadingIdle = false;

Papervision3D.log( "BitmapFileMaterial: Loading bitmap from " + file );
}
catch( error:Error )
{
// Remove from queue
_waitingBitmaps.shift();

// Loading finished
_loadingIdle = true;

Papervision3D.log( "[ERROR] BitmapFileMaterial: Unable to load file " + error.message );
}
}