Retrofit2遇到android.os.NetworkOnMainThreadException异常

APP中使用Retrofit2，在做下载功能时，惊喜的发现这个android.os.NetworkOnMainThreadException异常，抓到子线程去跑结果还是存在，后面试着把

@Streaming这个针对大文件下载的注解去掉后，功能正常，然后我还是想用@Streaming这个注解，但是又还存在这个异常，只能再度找度娘，最终总算解决了，看代码吧，肯定懂

private void Downs(){    new Thread(new Runnable() {        @Override        public void run() {            Call<ResponseBody> call = mResonServer.DownloadPic(list.get(positions));            try {                Response<ResponseBody> response = call.execute();//同步请求                File file = null;                if (response.isSuccessful()) {                    try {                        InputStream is = response.body().byteStream();                        if (!appDir.exists()) {                            appDir.mkdir();                        }                        String fileName = "Pic" + System.currentTimeMillis() + ".png";                        file = new File(appDir, fileName);                        FileOutputStream fos = new FileOutputStream(file);                        BufferedInputStream bis = new BufferedInputStream(is);                        byte[] buffer = new byte[1024];                        int len;                        while ((len = bis.read(buffer)) != -1) {                            fos.write(buffer, 0, len);                            fos.flush();                        }                        fos.close();                        bis.close();                        is.close();                        sendMsg("已保存到目录"+file.getAbsolutePath());                    } catch (IOException e) {                        e.printStackTrace();                        sendMsg("保存失败");                    }                } else {                    sendMsg("保存失败");                }                call.cancel();            } catch (IOException e) {                e.printStackTrace();                sendMsg("保存失败");            }        }    }).start();}//更新通知

private void sendMsg(String info){    msg = new Message();    b = new Bundle();    b.putString("info", info);    msg.setData(b);    handler.sendMessage(msg);}

这里的请求不是使用call.异步请求，而是使用同步请求,同时handler更新ui