<?xml version="1.0" encoding="utf-8"?> <s:WindowedApplication 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:Script> <![CDATA[ import flash.net.URLLoader; import flash.net.URLLoaderDataFormat; import flash.net.URLRequest; import flash.utils.ByteArray;   import mx.controls.Alert; [Bindable] private var progress:Number = 0; private var contentLength:int = 0; private var fileDir:File; private var file:File; private var startPoint:int = 0; private var endPoint:int = 0; private var rangeLoader:URLLoader;   private var range:int = 50000;   [Bindable] private var downloadStatus:Boolean = false;   private function init():void { var dotSplitLength:uint = videoURL.text.split("/").length;//这两行代码是为了获取下载文件的名称 var fileName:String = videoURL.text.split("/")[dotSplitLength-1]; var username:String = "iove86";//如果多用户，则这里取出用户名来建目录（我需要的功能） var downloadDir:String = "F:/myfiles/"+username+"/"; fileDir = new File(downloadDir);//File可以是文件也可以是目录，但是要用来创建目录时，显然不能为文件 try{ fileDir.createDirectory(); }catch(err:Error){ Alert.show("文件建立发生错误！","MSG"); } file = new File(downloadDir+fileName);//创建一个和下载文件名称一致的文件，保存在D盘temp目录下 }   private function doDownload():void {//先发送一个下载请求，可以得到文件的真实尺寸 var getContentLengthRequest:URLRequest = new URLRequest(videoURL.text); var getContentLengthLoader:URLLoader = new URLLoader(); getContentLengthLoader.addEventListener(ProgressEvent.PROGRESS ,function(e:ProgressEvent):void { contentLength = getContentLengthLoader.bytesTotal;//得到文件的真实尺寸 getContentLengthLoader.close();//停止下载 downloadByRange();//按照断点续传的方式下载 }); getContentLengthLoader.load(getContentLengthRequest); } private function downloadByRange():void {//按照断点续传的方式下载 downloadStatus = true; var fileStr:FileStream = new FileStream(); if(file.exists) {//如果文件是存在的，就说明下载过，需要计算从哪个点开始下载 fileStr.open(file, FileMode.READ); startPoint = fileStr.bytesAvailable;//计算从哪个点开始下载 fileStr.close();//关闭文件流 } trace("start:"+startPoint); if(startPoint+range > contentLength) {//确定下载的区间范围，比如0-10000 endPoint = contentLength; } else { endPoint = startPoint+range; } var rangeRequest:URLRequest = new URLRequest(videoURL.text); var header:URLRequestHeader = new URLRequestHeader("Range", "bytes="+startPoint+"-"+endPoint);//注意这里很关键，我们在请求的Header里包含对Range的描述，这样服务器会返回文件的某个部分 rangeRequest.requestHeaders.push(header);//将头信息添加到请求里 rangeLoader = new URLLoader(); rangeLoader.dataFormat = URLLoaderDataFormat.BINARY;//设置数据类型为字节 rangeLoader.addEventListener(Event.COMPLETE ,function(e:Event):void { var currentData:ByteArray = rangeLoader.data;//得到下载的数据 fileStr = new FileStream(); fileStr.open(file, FileMode.UPDATE); fileStr.position = fileStr.bytesAvailable;//将指针指向文件尾 fileStr.writeBytes(currentData, 0, currentData.length);//在文件中写入新下载的数据 fileStr.close();//关闭文件流 progress = endPoint/contentLength * 100;//计算下载进程 if(progress < 100) { downloadByRange();//如果下载没有完成，则执行下一个断点下载，直到下载完毕整个文件 } }); rangeLoader.load(rangeRequest);//发起请求 } private function pause():void {//暂停下载 downloadStatus = false; rangeLoader.close(); } private function open():void { file.openWithDefaultApplication(); } ]]> </fx:Script> <fx:Declarations> <!-- Place non-visual elements (e.g., services, value objects) here --> </fx:Declarations> <mx:Form x="29" y="26" width="50%" height="309"> <mx:FormItem label="URL"> <mx:TextInput id="videoURL" width="253" text="http://levis.ogilvy.com.cn/hk/media/background.mp3"/> </mx:FormItem> <mx:FormItem label="进度"> <mx:Label text="{progress+'%'}"/> </mx:FormItem> <mx:FormItem label="Label"> <mx:Button label="下载" click="doDownload();btDownload.visible=false" id="btDownload"/> </mx:FormItem> <mx:FormItem label="Label"> <mx:Button label="暂停" visible="{downloadStatus}" click="pause()"/> <mx:Button label="继续" visible="{!downloadStatus}" click="downloadByRange()"/> <mx:Button label="打开" visible="{progress==100}" click="open()"/> </mx:FormItem> </mx:Form> </s:WindowedApplication>