文件断点续传

 /**
     * 单线程支持断点续传下载
     * 断点续传
     */
    public static void downloadFile(final DownLoadProgressListener loadProgressListener) {
        Runnable runnable = new Runnable() {
            @RequiresApi(api = Build.VERSION_CODES.N)
            @Override
            public void run() {
                try {
                    URL url = new URL("https://codeload.github.com/yanzhenjie/Sofia/zip/master");
                    HttpURLConnection httpConnection = (HttpURLConnection) url.openConnection();
                    // 设置User-Agent
                    httpConnection.setRequestProperty("User-Agent", "NetFox");
                    //                    setHeader(httpConnection);
                    long bytes = AppConfig.getInstance().getLong("length", 0L);
                    // 得到content的长度

                    // 设置断点续传的开始位置
                    httpConnection.setRequestProperty("Range", "bytes=" + bytes + "-");
                    long contentLength = httpConnection.getContentLengthLong();
                    Log.i(TAG, "---" + "bytes=" + bytes + "-" + contentLength);
                    // 获得输入流
                    InputStream input = httpConnection.getInputStream();
                    File file = FileUtils.getLocalFile("Sofia.zip");
                    // 采用IO包中的RandAccessFile类。
                    RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");
                    long position = bytes;
                    //定位文件指针到nPos位置
                    accessFile.seek(position);
                    byte[] buffer = new byte[1024];
                    long total = position;
                    int statPosition = Integer.valueOf(position + "");
                    int len = -1;
                    long sTime = System.currentTimeMillis();
                    long eTime = 0;
                    int p = 0;
                    //跳过已经读取过的
                    long skipL = input.skip(position);
                    Log.i(TAG, " nStartPos --> " + position + ", skipL = " +
                            skipL);
                    //                    skipBytesFromStream(input, position);
                    //从输入流中读入字节流，然后写到文件中
                    while ((len = input.read(buffer, 0, 1024)) > 0) {
                        accessFile.write(buffer, 0, len);
                        total = total + len;
                        //记录文件日志长度
                        AppConfig.getInstance().putLong("length", total);

                        eTime = System.currentTimeMillis();
                        if (eTime - sTime > 200) {
                            //大于500ms 才进行一次监听
                            sTime = eTime;
                            Log.i(TAG, "file---Length:" + total);
                            loadProgressListener.onProgressUpdate(total, contentLength);
                        }
                    }
                    loadProgressListener.onCompleteLoad(contentLength);
                    Log.i(TAG, "file---end:" + total);
                } catch (IOException e) {
                    e.printStackTrace();
                    loadProgressListener.onError(0);
                }

            }
        };
        AppContext.MAIN_EXECUTOR.execute(runnable);
    }

    public interface DownLoadProgressListener {
        void onProgressUpdate(long percent, long length);

        void onCompleteLoad(long length);

        void onError(int error);
    }