URLStream,URLLoader和Loader

URLSteam读取文本文件可以支持多种编码

URLLoader如果遇到乱码,则可以转换（就像上篇说的利用标准的xml格式Excle可以解决乱码问题就是基于这里）：

1.         var ba:ByteArray = new ByteArray;  
2.         ba.writeBytes((event.target as URLLoader).data);  
3.         ba.position = 0;  
4.         //假如记载的是xml文档
5.         var xml:XML = XML(ba.readMultiByte(ba.length, "GBK"));

loader用于加载外部的图片文件，SWF文件等。我之前在一个air里面用到它来上载图片，并且要生成一个缩略图，实现代码如下：

1.             //import的相关
2.             import mx.events.CloseEvent;
3.             import flash.geom.Matrix;
4.             import mx.graphics.codec.JPEGEncoder;
5.             import mx.graphics.codec.PNGEncoder;
6.             import mx.controls.Image;
7.             import mx.controls.Alert;
8.             import mx.utils.ArrayUtil;
9.             import mx.collections.ArrayCollection;
10.             import mx.formatters.NumberFormatter;
11.             import mx.messaging.AbstractConsumer;
12.             
13.             
14.             //压缩小图的相关信息信息
15.             private var SmallPicSize:int = 80;
16.             //保存相片的扩展名列表
17.             private static const EXT_JPEG:String = "jpg";
18.             private static const EXT_PNG:String = "png";        
19.         
20.         
21.         
22.         
23.             public function browseAndUpload():void
24.             {
25.                 var FileToOpen:File = File.documentsDirectory;
26.                 var txtFilter:FileFilter = new FileFilter("jpg,png","*.jpg;*png;"); 
27.                 FileToOpen.browseForOpen("Open", [txtFilter]); 
28.                 FileToOpen.addEventListener(Event.SELECT,FileToOpenSelected);   
29.             }
30.             //当上载的相片被打开后，就进行上载操作
31.             private function FileToOpenSelected(objEvent:Event):void 
32.             {
33.                 var OrgImgPath:String = File(objEvent.currentTarget).nativePath;
34.                 try
35.                 {
36.                     var orgFile:File = new File(OrgImgPath);
37.                     //获取一个随机的图片名称
38.                     var curPicName:String = "TestUploadPic."+orgFile.extension;
39.                     //假如我们把图片的大图片放到项目的/upload/big/文件夹下
40.                     var bigImgFile:File = new File(File.applicationDirectory.nativePath+"/upload/big/"+curPicName);
41.                     orgFile.copyTo(bigImgFile); 
42.                     //获取原图的bitmap信息，然后重构一个小图放到temp/small/文件夹下面
43.                     var loader:Loader = new Loader();
44.                     //使用内联函数在事件中传递参数
45.                     var mySpecialObject:Object = {NewImgName:curPicName,NewImgExt:orgFile.extension};
46.                     //注意是loader.contentLoaderInfo
47.                     loader.contentLoaderInfo.addEventListener(Event.COMPLETE,function (e:Event) : void {loadComplete(e,mySpecialObject);});
48.                     loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR,loadError);
49.                     //加载原图
50.                     var request:URLRequest = new URLRequest(orgFile.nativePath);
51.                     loader.load(request);
52.                 }
53.                 catch(er:Error)
54.                 {
55.                     Alert.show(er.message);
56.                 }
57.             }
58.             
59.              //在上载的过程中把原图也load进了内存，主要目的是用原图来生成一个小图，load这个动作完成后的处理方法 
60.             public function loadComplete(event:Event,objSpecial:Object):void
61.             {
62.                 try
63.                 {
64.                     if(objSpecial != null && objSpecial.NewImgName.toString() != "")
65.                     {
66.                         var loader:Loader = Loader(event.target.loader);
67.                         var BigBitmapdata:BitmapData = Bitmap(loader.contentLoaderInfo.content).bitmapData;
68.                         var myscale:Number = 1.0;
69.                         if(BigBitmapdata.width > 120 || BigBitmapdata.height > 100)
70.                         {
71.                             if(BigBitmapdata.width > BigBitmapdata.height)
72.                             {
73.                                 myscale = 120/BigBitmapdata.width;
74.                             }else
75.                             {
76.                                 myscale = 100/BigBitmapdata.height;
77.                             }
78.                         }
79.                         //创建新转换矩阵
80.                         var m:Matrix = new Matrix();
81.                         m.scale(myscale,myscale);
82.                         var SmallBitmapdata:BitmapData = new BitmapData(BigBitmapdata.width*myscale,BigBitmapdata.height*myscale,BigBitmapdata.transparent,0xFFFFFFFF); 
83.                         SmallBitmapdata.draw(BigBitmapdata,m);
84.                         //相片的Bytearray
85.                         var imgByteArray:ByteArray;
86.                         switch(objSpecial.NewImgExt.toString())
87.                         {
88.                             case EXT_JPEG:
89.                                 var jpgenc:JPEGEncoder = new JPEGEncoder(80);
90.                                 imgByteArray = jpgenc.encode(SmallBitmapdata);
91.                                 break;
92.                             case EXT_PNG:
93.                                 var pngenc:PNGEncoder = new PNGEncoder();
94.                                 imgByteArray = pngenc.encode(SmallBitmapdata);
95.                                 break;
96.                         }
97.                         //假如我们把图片的大图片放到项目的/upload/small/文件夹下
98.                         var smallFile:File = new File(File.applicationDirectory.nativePath+"/upload/small/"+objSpecial.NewImgName.toString());
99.                         var fs:FileStream = new FileStream();
100.                         try{
101.                             
102.                             fs.open(smallFile,FileMode.WRITE);
103.                             fs.writeBytes(imgByteArray);
104.                             fs.close();
105.                         }catch(e:Error){
106.                             Alert.show(e.message);
107.                         }   
108.                         
109.                         //释放BitmapData所占用的内存(很重要)
110.                         BigBitmapdata.dispose();
111.                         SmallBitmapdata.dispose();
112.                     }   
113.                 }
114.                 catch(err:Error)
115.                 {
116.                     Alert.show("生成小图片出错.");
117.                 }
118.             }
119.             //当load原图的时候出错的处理方法 
120.             public function loadError(event:IOErrorEvent):void
121.             {
122.                 Alert.show("上载的图片源："+Loader(event.target.loader).contentLoaderInfo.loaderURL.toString()+"不存在,无法生成小图");
123.             }