air保存文件路径

import flash.events.MouseEvent;
import flash.filesystem.File;
import flash.filesystem.FileStream;
import flash.events.Event;

var mainfile:File = File.documentsDirectory;
mainfile =mainfile.resolvePath(mainfile.url + "/mydata/" + "mainfile.txt");
if (mainfile.exists)
{ 
 trace("存在");
}
else
{
    directory.browseForDirectory("Select Directory");
    directory.addEventListener(Event.SELECT, directorySelected);
 
 
}

function directorySelected(event:Event):void
{
    directory = event.target as File;
    var fileStream:FileStream = new FileStream();
    fileStream.open(mainfile, FileMode.WRITE);
    fileStream.writeUTFBytes(directory.nativePath);
}