var ff:File = File.desktopDirectory.resolvePath("Progress.CSV");
 ff.addEventListener(Event.SELECT,exportCSVSelectedHandler);
 ff.browseForSave("选择路径");
 
private function exportCSVSelectedHandler(event:Event):void
 {
 var dir:String = event.target.nativePath;
 var writeStream:FileStream = new FileStream();
 writeStream.open(new File(dir),FileMode.WRITE);
 var content:String = "jhfdklahflaksjdhflkasjhflaskjhlf\n";
 writeStream.writeMultiByte(content,'utf-8');
 writeStream.close();
 }
 

var content:String = "jhfdklahflaksjdhflkasjhflaskjhlf\n";
 
var f:FileReference = new FileReference();
 f.save(content,"1.csv");