private void downloadFile2(){//下载路径，如果路径无效了，可换成你的下载路径String url = "http://c.qijingonline.com/test.mkv";//创建下载任务,downloadUrl就是下载链接DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));//指定下载路径和下载文件名request.setDestinationInExternalPublicDir("", url.substring(url.lastIndexOf("/") + 1));//获取下载管理器DownloadManager downloadManager= (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);//将下载任务加入下载队列，否则不会进行下载downloadManager.enqueue(request);
}

private void downloadFile3(){//下载路径，如果路径无效了，可换成你的下载路径final String url = "http://c.qijingonline.com/test.mkv";final long startTime = System.currentTimeMillis();Log.i("DOWNLOAD","startTime="+startTime);Request request = new Request.Builder().url(url).build();new OkHttpClient().newCall(request).enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {// 下载失败e.printStackTrace();Log.i("DOWNLOAD","download failed");}@Overridepublic void onResponse(Call call, Response response) throws IOException {Sink sink = null;BufferedSink bufferedSink = null;try {String mSDCardPath= Environment.getExternalStorageDirectory().getAbsolutePath();File dest = new File(mSDCardPath,   url.substring(url.lastIndexOf("/") + 1));sink = Okio.sink(dest);bufferedSink = Okio.buffer(sink);bufferedSink.writeAll(response.body().source());bufferedSink.close();Log.i("DOWNLOAD","download success");Log.i("DOWNLOAD","totalTime="+ (System.currentTimeMillis() - startTime));} catch (Exception e) {e.printStackTrace();Log.i("DOWNLOAD","download failed");} finally {if(bufferedSink != null){bufferedSink.close();}}}});
}

okhttp是一个很有名气的开源框架，目前已经很多大公司都直接使用它作为网络请求库（七牛云SDK， 阿里云SDK）。 且里面集成了很多优势，包括 okio (一个I/O框架，优化内存与CPU)。

综合来看，第三种方案是最佳的，是目前最流行的下载方案。