flex 加载图片的同时获取加载图片的大小

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx"  creationComplete="init()" >
<fx:Declarations>
<!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>
<fx:Script>
<![CDATA[
import flash.events.*;
import flash.net.FileFilter;
import flash.net.FileReference;
import mx.controls.Image;

private var fileReference:FileReference;
private var byteArray:ByteArray;
private var bitmapData:BitmapData;
private var loader:Loader;
private var winDIVTitle:String = "图片加载至内存显示预览";

public function init():void
{
fileReference = new FileReference();
loader = new Loader();
configureListeners(fileReference);
}

private function configureListeners(dispatcher:IEventDispatcher):void {
dispatcher.addEventListener(Event.CANCEL, cancelHandler);
dispatcher.addEventListener(Event.COMPLETE, completeHandler);
dispatcher.addEventListener(HTTPStatusEvent.HTTP_STATUS, httpStatusHandler);
dispatcher.addEventListener(IOErrorEvent.IO_ERROR, ioErrorHandler);
dispatcher.addEventListener(Event.OPEN, openHandler);
dispatcher.addEventListener(ProgressEvent.PROGRESS, progressHandler);
dispatcher.addEventListener(SecurityErrorEvent.SECURITY_ERROR, securityErrorHandler);
dispatcher.addEventListener(Event.SELECT, selectHandler);
dispatcher.addEventListener(DataEvent.UPLOAD_COMPLETE_DATA,uploadCompleteDataHandler);
}

private function getTypes():Array {
var allTypes:Array = new Array(getImageTypeFilter());
return allTypes;
}

private function getImageTypeFilter():FileFilter {
return new FileFilter("Images (*.jpg, *.jpeg, *.gif, *.png)", "*.jpg;*.jpeg;*.gif;*.png");
}

private function cancelHandler(event:Event):void {
trace("cancelHandler: " + event);
}

/***
* 文件选择完成之后
* */
private function completeHandler(event:Event):void
{
trace("completeHandler: " + event);
byteArray = fileReference.data;
loader.contentLoaderInfo.addEventListener(Event.COMPLETE,loaderCompleteHandler);
loader.loadBytes(byteArray);
}

private function loaderCompleteHandler(e:Event):void
{
var bitmap:Bitmap = Bitmap(loader.content);
bitmapData = bitmap.bitmapData;
img.source = new Bitmap(bitmapData,"auto",true); ;
/***矫正图片 让图片自动适应容器***/
imgLoadFinish(e);
}

private function uploadCompleteDataHandler(event:DataEvent):void {
trace("uploadCompleteData: " + event);
img.addEventListener(Event.COMPLETE, imgLoadFinish);

}

private function httpStatusHandler(event:HTTPStatusEvent):void {
trace("httpStatusHandler: " + event);
}

private function ioErrorHandler(event:IOErrorEvent):void {
trace("ioErrorHandler: " + event);
}

private function openHandler(event:Event):void {
trace("openHandler: " + event);
}

private function progressHandler(event:ProgressEvent):void {
var file:FileReference = FileReference(event.target);
trace("progressHandler name=" + file.name + " bytesLoaded=" + event.bytesLoaded + " bytesTotal=" + event.bytesTotal);
}

private function securityErrorHandler(event:SecurityErrorEvent):void {
trace("securityErrorHandler: " + event);
}

private function selectHandler(event:Event):void {
var file:FileReference = FileReference(event.target);
trace("selectHandler: name=" + file.name);
//file.upload(uploadURL);
/**将文件加载至内存，预览出来**/
fileReference.load();
}

private function btnClick():void
{
fileReference.browse(getTypes());
}

private function imgLoadFinish(evt:Event):void
{
//原始图片的大小   --- 第一次加载的时候这种方法获取不到图片的真实大小
//var real_width:Number = img.contentWidth ;
//var real_height:Number = img.contentHeight;

var real_width:Number = evt.currentTarget.content.width;
var real_height:Number = evt.currentTarget.content.height;
//容器的大小
var flashWidth:Number = divMain.width;
var flashHeight:Number = divMain.height;

//Alert.show("图片源文件大小："+ real_width +" * " +real_height + "\n" + "容器大小： " + flashWidth +" * " +flashHeight,"容器、图片尺寸信息" );

//比值
var w_bi:Number = real_width/width;
var h_bi:Number = real_height/height;

if(w_bi < 1 && h_bi <1)
{
//第一次也不行 不能真正获取到真实大小
//img.width = img.content.width;
//img.height = img.content.height;

img.width = evt.currentTarget.content.width;
img.height = evt.currentTarget.content.height;

//Alert.show("img大小："+ img.content.width +" * " + img.content.height + "\n" + "evt大小： " + evt.currentTarget.content.width +" * " + evt.currentTarget.content.height,"w_bi < 1 && h_bi <1" );
//Alert.show("图片宽高都比容器小");
}
else
{
if(w_bi > h_bi)
{
img.width = flashWidth;
img.height = real_height * flashWidth / real_width;
//Alert.show("w_bi > h_bi" + img.width + "* " + img.height);
}
else
{
img.height = flashHeight;
img.width = real_width * flashHeight / real_height;
//Alert.show("w_bi < h_bi"  + img.width + "* " + img.height);
}
}
img.x = (flashWidth - img.width) / 2;
img.y = (flashHeight - img.height) / 2;

fileInfo.text = fileReference.name + "源文件大小（ "+ real_width +" * " +real_height+"）";
}

]]>
</fx:Script>
<s:Panel x="151" y="41" width="574" height="410" id="winDIV" title="{winDIVTitle}" horizontalCenter="0" verticalCenter="0" >
<mx:Canvas x="10" y="10" width="552" height="323" id="divMain" horizontalScrollPolicy="off" verticalScrollPolicy="off">
<mx:Image id="img"  horizontalAlign="center" verticalAlign="middle" />
</mx:Canvas>
<s:Button x="480" y="341" label="浏览文件" id="scan" height="30" width="83" click="btnClick()"/>
<s:Label x="10" y="341" width="451" height="26" id="fileInfo" verticalAlign="middle"/>
</s:Panel>
</s:Application>