更新下载

最新推荐文章于 2021-11-17 14:29:28 发布
转载最新推荐文章于 2021-11-17 14:29:28 发布 · 260 阅读
本文介绍了一种基于多线程技术实现的大文件下载方法，通过将文件分割成多个部分并行下载，有效提高了下载速度。文章详细展示了如何利用Java进行HTTP连接配置，设置断点续传，并通过进度条实时显示下载进度。
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public class NetUtils {
    public static void downloadFile(String downloadUrl, String path, int blockSize, int startPosition){
        BufferedInputStream bis = null;
        RandomAccessFile raf = null;
        try {
            File f = new File(path);
            if(!f.exists()){
                f.createNewFile();
            }
            URL url = new URL(downloadUrl);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(8000);
            conn.setConnectTimeout(8000);

//            long start = 0;
            if(blockSize > 0){
//                //使用线程id来计算 当前线程的开始位置和结束位置
//                start = blockSize * threadId;
                long end = blockSize + startPosition - 1;
                //多线程下载  需要告诉服务器我要请求的是哪部分内容  需要写在请求头里面
                conn.setRequestProperty("Range", "bytes=" + startPosition + "-" + end);

                Log.i(Thread.currentThread() + "======", "bytes=" + startPosition + "-" + end);
            }


            int code = conn.getResponseCode();
            if(code < 400){
                bis = new BufferedInputStream(conn.getInputStream());
                raf = new RandomAccessFile(f, "rwd");
                //
                raf.seek(startPosition);
                //
                int len = 0;
                byte[] buff = new byte[1024 * 8];
                while((len = bis.read(buff)) != -1){
                    synchronized (NetUtils.class){
                        raf.write(buff, 0, len);
                       if (DialogUtils.PROGRESS  <  0 ){
                           DialogUtils.PROGRESS = 0;
                       }
                        DialogUtils.PROGRESS += len;
                    }
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if(bis != null){
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(raf != null){
                try {
                    raf.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }

    public static int getFileLength(String downloadUrl){
        int len = 0;
        try {
            URL url = new URL(downloadUrl);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(8000);
            conn.setConnectTimeout(8000);

            len = conn.getContentLength();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return len;
    }
}









public class DownloadThread extends Thread{
    private String downloadUrl = "";
    private String path;
    private int threadNum ;

    public DownloadThread(String downloadUrl, String path, int threadNum) {
        this.downloadUrl = downloadUrl;
        this.path = path;
        this.threadNum = threadNum;
    }

    @Override
    public void run() {
        int len = NetUtils.getFileLength(downloadUrl);
        DialogUtils.MAX_SIZE = len;

        //例如  1000kb  3   333
        int blockSize = len/threadNum;
//        //四舍五入---  让一个数字+0。5在四舍五入 就变成 向上取整
//        int blockSize = (int) Math.round(tempSize + 0.5);

        //计算出下载块以后   创建线程执行下载操作
        for (int i = 0; i < threadNum; i++) {
            //计算开始位置
            int startPosition = blockSize * i;
            //让最后一个线程下载的大小是正好的，  总长度 - 除了最后一个块的大小和
            if(i == threadNum - 1){
                blockSize = len - blockSize * (threadNum - 1);
            }
            new DownloadTask(downloadUrl, path, blockSize, startPosition).start();
        }


    }

}







public class DownloadTask extends Thread{
    String downloadUrl;
    String path;
    int blockSize;
    int startPosition;

    public DownloadTask(String downloadUrl, String path, int blockSize, int startPosition) {
        this.downloadUrl = downloadUrl;
        this.path = path;
        this.blockSize = blockSize;
        this.startPosition = startPosition;
    }

    @Override
    public void run() {
        NetUtils.downloadFile(downloadUrl,path,blockSize,startPosition);
    }
}






public class DialogUtils {
    public static long MAX_SIZE = 0;
    public static long PROGRESS = -2;

    public static void showUpdataDialog(final Context context) {
        AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setTitle("是否更新")
                .setMessage("太旧了，更新吧")
                .setNegativeButton("就不", null)
                .setPositiveButton("可以", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        new DownloadThread("http://169.254.177.227:8080/tm/alipay_wap_main.apk", context.getCacheDir() + "/alipay_wap_main.apk", 5).start();
                        showProgress(context);
                    }
                }).show();
    }

    public static void showProgress(final Context context) {
        final ProgressDialog pd = new ProgressDialog(context);
        pd.setTitle("正在更新");
        pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        pd.setMax(100);
        pd.show();

        new AsyncTask<String, Integer, String>() {

            @Override
            protected String doInBackground(String... strings) {
                while (PROGRESS + 1 < MAX_SIZE) {
                    SystemClock.sleep(100);
                    if (MAX_SIZE > 0) {
                        publishProgress((int) (PROGRESS * 100 / MAX_SIZE));
                    }


                }
                return null;
            }

            @Override
            protected void onPostExecute(String s) {
                super.onPostExecute(s);
                pd.dismiss();

                File file = new File(context.getCacheDir() + "/alipay_wap_main.apk");

//                String[] command = {"chmod", "777", file.getPath() };
//                ProcessBuilder builder = new ProcessBuilder(command);
//                try {
//                    builder.start();
//                } catch (IOException e) {
//                    e.printStackTrace();
//                }

                String command2 = "chmod " + "777" + " " + file.getPath();
                Runtime runtime = Runtime.getRuntime();
                try {
                    runtime.exec(command2);
                } catch (IOException e) {
                    e.printStackTrace();
                }


                Intent intent = new Intent(Intent.ACTION_VIEW);
                 // 由于没有在Activity环境下启动Activity,设置下面的标签
                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                intent.setDataAndType(Uri.fromFile(file),
                        "application/vnd.android.package-archive");
                context.startActivity(intent);
            }

            @Override
            protected void onProgressUpdate(Integer... values) {
                super.onProgressUpdate(values);
                pd.setProgress(values[0]);
            }
        }.execute();
    }
}