Question

我正在尝试创建一个可以帮助我评估从Web资源下载文件的时间的应用程序。我找到了2个样本：

Download a file with Android, and showing the progress in a ProgressDialog

和

http://www.helloandroid.com/tutorials/how-download-fileimage-url-your-device

第二个示例显示较小的下载时间，但我无法理解如何使用它更新进度对话框。我觉得应该用第二种情况下的“while”表达来完成，但我找不到什么。有人可以给我任何建议吗？

UPD：

第一个代码：

try {
            time1 = System.currentTimeMillis();
            URL url = new URL(path);
            URLConnection conexion = url.openConnection();
            conexion.connect();
            // this will be useful so that you can show a tipical 0-100% progress bar
            int lenghtOfFile = conexion.getContentLength();
            // downlod the file
            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream("/sdcard/analyzer/test.jpg");

            byte data[] = new byte[1024];

            long total = 0;

          time11 = System.currentTimeMillis();
           while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                publishProgress((int)(total*100/lenghtOfFile));
                output.write(data, 0, count);
            }
            time22= System.currentTimeMillis()-time11;
            output.flush();
            output.close();
            input.close();


        } catch (Exception e) {}

        timetaken = System.currentTimeMillis() - time1;

第二段代码：

       long time1 = System.currentTimeMillis();
        DownloadFromUrl(path, "test.jpg");
        long timetaken = System.currentTimeMillis() - time1;

其中

  public void DownloadFromUrl(String imageURL, String fileName) {  //this is the downloader method
 try {
         URL url = new URL(imageURL); //you can write here any link
         File file = new File(fileName);

        /*Open a connection to that URL. */
         URLConnection ucon = url.openConnection();

         /*
          * Define InputStreams to read from the URLConnection.
          */
         InputStream is = ucon.getInputStream();
         BufferedInputStream bis = new BufferedInputStream(is);

         /*
          * Read bytes to the Buffer until there is nothing more to read(-1).
          */
         ByteArrayBuffer baf = new ByteArrayBuffer(50);
         int current = 0;
         while ((current = bis.read()) != -1) {
                 baf.append((byte) current);
         }

         /* Convert the Bytes read to a String. */
         FileOutputStream fos = new FileOutputStream(PATH+file);
         fos.write(baf.toByteArray());
         fos.close();

 } catch (IOException e) {
         Log.d("ImageManager", "Error: " + e);
 }

所以问题是第一种方法似乎比较慢约30％。

Answer 1

second example可能会运行得更快，但它会独占GUI线程。使用first approach的AsyncTask更好;它允许GUI在下载过程中保持响应。

我发现将AsyncTask与SwingWorker进行比较会很有帮助，如example所示。

Answer 2

第一个链接是最好的。但我无法在星期一或之后提供代码（它的家庭补偿），我可以提供全部功能。但是：

private class DownloadFile extends AsyncTask<String, Integer, String>{
    @Override
    protected String doInBackground(String... url) {
        int count;
        try {
            URL url = new URL(url[0]);
            URLConnection conexion = url.openConnection();
            conexion.connect();
            // this will be useful so that you can show a tipical 0-100% progress bar
            int lenghtOfFile = conexion.getContentLength();

            // downlod the file
            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream("/sdcard/somewhere/nameofthefile.ext");

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                publishProgress((int)(total*100/lenghtOfFile));
                output.write(data, 0, count);
            }

            output.flush();
            output.close();
            input.close();
        } catch (Exception e) {}
        return null;
    }

这个班级最适合它（imho）。 publishProgress它的简单功能，你有最多两行。设置最大值并设置当前值。你在这段代码中可以看到lenghtOfFile它是多少字节有你的文件。 total - 当前进度（示例25来自100字节）。轻松运行这个课程：DownloadFile a = new DownloadFile(); a.execute(value,value);//or null if u not using value.希望你理解我，我不会用英语说话。

更新进度对话框

2 个答案: