Flex中使用FileReference类下载文件
下面的实例演示了Flex中的 FileReference 类的基本用法，允许用户从服务器上下载一个文件。这个例子也演示了你可以在 DataGrid组件中显示数据提示（data tips） ，只要把 data grid column 的 showDataTips 属性设置为 true ，然后把 column 的 dataTipField 设置一个值就行了。
在下边的演示中，当用户点击按钮的时候会下载一个 zip 文件 ，然后你可以把鼠标移到 DataGrid 组件的 Type 列上，来看额外的 Event 信息。
?
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" verticalAlign="middle" backgroundColor="white" creationComplete="init();">
??
??<mx:Script>
????<![CDATA[
??????import mx.controls.Alert;
??????import mx.collections.ArrayCollection;
??????import flash.net.FileReference;
??????[Bindable]
??????[Embed('assets/disk.png')]
??????private var diskIcon:Class;
??????
??????[Bindable]
??????private var arrColl:ArrayCollection;
??????// 要下载文件的URL
??????private const FILE_URL:String = "http://www.nshen.net/blog/doc/flex/FileReference_download_test/FileReference_download_test.zip";
??????private var fileRef:FileReference;
??????private var urlReq:URLRequest;
??????
??????private function init():void {
????????// 初始化一个空ArrayCollection
????????arrColl = new ArrayCollection();
????????
????????// 以FILE_URL指定的地址建立一个URLRequest
????????urlReq = new URLRequest(FILE_URL);
????????
????????// 定义一个FileReference对象，并填加一系列事件监听
????????fileRef = new FileReference();
????????fileRef.addEventListener(Event.CANCEL, doEvent);
????????fileRef.addEventListener(Event.COMPLETE, doEvent);
????????fileRef.addEventListener(Event.OPEN, doEvent);
????????fileRef.addEventListener(Event.SELECT, doEvent);
????????fileRef.addEventListener(HTTPStatusEvent.HTTP_STATUS, doEvent);
????????fileRef.addEventListener(IOErrorEvent.IO_ERROR, doEvent);
????????fileRef.addEventListener(ProgressEvent.PROGRESS, doEvent);
????????fileRef.addEventListener(SecurityErrorEvent.SECURITY_ERROR, doEvent);
??????}
??????
??????private function doEvent(evt:Event):void {
????????// 取得当前FileReference的引用
????????var fr:FileReference = evt.currentTarget as FileReference;
????????
????????// 填加事件顺序和类型到DataGrid组件
????????arrColl.addItem({data:arrColl.length+1, type:evt.type, eventString:evt.toString()});
????????try {
??????????// 更新 Model.
??????????fileRefModel.creationDate = fr.creationDate;
??????????fileRefModel.creator = fr.creator;
??????????fileRefModel.modificationDate = fr.modificationDate;
??????????fileRefModel.name = fr.name;
??????????fileRefModel.size = fr.size;
??????????fileRefModel.type = fr.type;
??????????// 显示文本
??????????txt.visible = true;
????????} catch (err:*) {
??????????// uh oh, an error of sorts.
????????}
??????}
??????private function downloadSourceCodeZip():void {
????????// 清空现有的 array collection.
????????arrColl = new ArrayCollection();
????????// 隐藏文本组件
????????txt.visible = false;
????????// 开始下载
????????fileRef.download(urlReq);
??????}
??????
??????private function showAlert(item:Object):void {
????????Alert.show(item.eventString, item.type);
??????}
????]]>
??</mx:Script>
??
??<mx:Model id="fileRefModel">
????<file>
??????<creationDate>{""}</creationDate>
??????<creator>{""}</creator>
??????<modificationDate>{""}</modificationDate>
??????<name>{""}</name>
??????<size>{""}</size>
??????<type>{""}</type>
????</file>
??</mx:Model>
??
??<mx:Button id="downloadBtn" label="Download example source code" icon="{diskIcon}" click="downloadSourceCodeZip()" toolTip="{FILE_URL}" height="40" />
??<mx:DataGrid id="debug" dataProvider="{arrColl}" width="{downloadBtn.width}" rowCount="5" rowHeight="22" itemClick="showAlert(event.currentTarget.selectedItem)">
????<mx:columns>
??????<mx:DataGridColumn dataField="data" headerText="#" width="20" />
??????<mx:DataGridColumn dataField="type" headerText="Type" showDataTips="true" dataTipField="eventString" />
????</mx:columns>
??</mx:DataGrid>
??
??<mx:Text id="txt" condenseWhite="true" visible="false">
????<mx:text>
????creationDate: {fileRefModel.creationDate}
????creator: {fileRefModel.creator}
????modificationDate: {fileRefModel.modificationDate}
????name: {fileRefModel.name}
????size: {fileRefModel.size}
????type: {fileRefModel.type}
????</mx:text>
??</mx:Text>
</mx:Application>
