try {
            File file = getFile(fileName);
            BufferedSink sink = Okio.buffer(Okio.sink(file));
            Buffer buffer = sink.buffer();
            long readSize = 0, length = body.contentLength(), read;
            int step = 4069;
            BufferedSource source = body.source();
            DownloadInfo info = new DownloadInfo(length);
            while ((read = source.read(buffer, step)) != -1) {
                readSize += read;
                info.setReadFileSize(readSize);
                Utils.d("Better", "下载了==" + readSize + ",total=" + length);
                subscriber.onNext(info);
            }
//             you can access body of response
//            sink.writeAll(body.source());
            sink.close();
//            subscriber.onNext(null);
            subscriber.onCompleted();
        } catch (Exception e) {
            e.printStackTrace();
            subscriber.onError(e);
        }