网上没有找到相关的文章，写下来自己记一下
直接上代码：
downFile2Local:function(url, fileName, callback){
var fullPath = jsb.fileUtils.getWritablePath() + fileName
showModelLoadingDialog();//显示加载中模态框
var downloader = new jsb.Downloader();
downloader.setOnFileTaskSuccess(function(){
removeModelLoadingDialog();//删除加载中模态框
if(callback){
callback(fullPath);
}
});
downloader.setOnTaskError(function(){
removeModelLoadingDialog();
showTips("文件下载失败！！！");
});
downloader.createDownloadFileTask(url, fullPath);//创建下载任务
}