文件下载例子

接下来的例子演示了Flex中如何利用Flash播放器的FileReference类(flash.net.FileReference)，从服务器端下载文件到本地。在这个例子中，同样还可以了解DataGrid中通过设置showDataTips属性为True并且在dataTipField列中指定一个值。

<?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;   
  
            /* URL of the file to download. */ 
            private const FILE_URL:String = "http://blog.minidx.com/ext/downloading-files-in-flex-using-the-filereference-class/srcview/main.zip";   
  
            private var fileRef:FileReference; 
            private var urlReq:URLRequest;   
  
            private function init():void { 
                /* Initialize the array collection to an empty collection. */ 
                arrColl = new ArrayCollection();   
  
                /* Set up the URL request to download the file specified by the FILE_URL variable. */ 
                urlReq = new URLRequest(FILE_URL);   
  
                /* Define file reference object and add a bunch of event listeners. */ 
                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 { 
                /* Create shortcut to the FileReference object. */ 
                var fr:FileReference = evt.currentTarget as FileReference;   
  
                /* Add event order and type to the DataGrid control. */ 
                arrColl.addItem({data:arrColl.length+1, type:evt.type, eventString:evt.toString()});   
  
                try { 
                    /* Update the 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; 
                    /* Display the Text control. */ 
                    txt.visible = true; 
                } catch (err:*) { 
                    /* uh oh, an error of sorts. */ 
                } 
            }   
  
            private function downloadSourceCodeZip():void { 
                /* Clear existing array collection. */ 
                arrColl = new ArrayCollection(); 
                /* Hide the Text control. */ 
                txt.visible = false; 
                /* Begin download. */ 
                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>