Flex中进度条的使用

样张图：
使用方法：
设置Application标签的preloader为 MyComponent.MyDownloadProgressBar
<mx:Application preloader="MyComponent.MyDownloadProgressBar" >
下面是MyDownloadProgressBar.as的代码：
package MyComponent
{
import flash.display.*;
import flash.events.*;
import flash.filters.BitmapFilterQuality;
import flash.filters.BlurFilter;
import flash.geom.Matrix;
import flash.net.*;
import flash.text.TextField;
import flash.utils.*;
import flash.system.Capabilities;
import mx.events.*;
import mx.preloaders.*;
public class MyDownloadProgressBar extends Sprite implements IPreloaderDisplay
{       
[Embed(source="logo.png", mimeType="application/octet-stream")]
public var _loadingLogo:Class;
private var dpbImageControl:Loader;
private var _barSprite:Sprite;
private var progressText:TextField;       
private var ProgressBarSpritIsAdded:Boolean = false;
public function MyDownloadProgressBar() {  
super();                           
}
// Specify the event listeners.
public function set preloader(preloader:Sprite):void {
//Listen for 正在下载
preloader.addEventListener(ProgressEvent.PROGRESS, handleProgress);
//Listen for 下载完成
preloader.addEventListener(Event.COMPLETE, handleComplete);
//Listen for 正在初始化
preloader.addEventListener(FlexEvent.INIT_PROGRESS, handleInitProgress);
//Listen for 初始化完成
preloader.addEventListener(FlexEvent.INIT_COMPLETE, handleInitComplete);
}
// Initialize the Loader control in the override
// of IPreloaderDisplay.initialize().
public function initialize():void {
//添加logo图
dpbImageControl = new Loader();      
dpbImageControl.contentLoaderInfo.addEventListener(Event.COMPLETE, loader_completeHandler);