android利用url下载的mp3为什么不完整10秒只下了不到7秒？

URL url = new URL("http://www.ipmidi.com:8080/"+fileType+fileUrl);
HttpURLConnection UrlCon=(HttpURLConnection) url.openConnection();
//UrlCon.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.19 Safari/537.36");
UrlCon.setConnectTimeout(5 * 1000);
InputStream is=UrlCon.getInputStream();
Log.e(TAG, "网址读取结束");
File file = new File(fileLocal);

OutputStream output = new FileOutputStream(file);

int len = 0;
//byte b=127;
byte[] buffer=new byte[1024];
Log.e(TAG, "文件读取开始");
while((len = is.read(buffer))!=-1){
output.write(buffer,0,len);
}
output.flush();
output.close();
is.close();

                    网址：http://www.ipmidi.com:8080/mp3/104_E1.mp3

感觉下载框架有问题，https://github.com/dvlp-org/DvlpOkHttp，用这个框架试试，demo里面有下载功能