Question

Description:
I have a grid view with 4 items in landscape mode and 3 items on portrait mode. The grid element is a magazine thumbnail. On click of a thumbnail downloading of the magazine starts and a horizontal progress bar appears showing progress of download. But when i click to two thumbnails one after another , the progress bar of later clicked thumbnail only updates and at last corrupted magazine gets downloaded.
I have used asynchronous task for magazine download.

Code:

public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {


    progress = (ProgressBar) arg1.findViewById(R.id.progress);
    thumbnail = (ImageView) arg1.findViewById(R.id.thumbnail);



    thumbnail.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // Download Magazine
             downloadMagazine.execute(bank.get(index).getPdfLink());

            }
    });

}


class DownloadMagazineTask extends AsyncTask<String, Integer, Long> {
    File sdDir = Environment.getExternalStorageDirectory();

    @Override
    protected void onPreExecute() {

       progress.setVisibility(View.VISIBLE);

    }

    @Override
    protected Long doInBackground(String... arg0) {

        String[] urls = arg0;

        try {
            URL url = new URL(urls[0]);
            URLConnection con = url.openConnection();
            int fileLength = con.getContentLength();

            InputStream input = new BufferedInputStream(url.openStream());

            File file = null;

            File dir = new File(sdDir + "/BeSpoken/pdfs");
            boolean flag = dir.mkdirs();
            if (flag)

                System.out.println("Directory created");
            else {
                System.out.println("Directory not created");
                file = new File(dir+ "/"+ bank.get(index).getPdfLink().substring(bank.get(index).getPdfLink().lastIndexOf("/")));

            }
            OutputStream output = new FileOutputStream(file);

            byte data[] = new byte[1024];
            long total = 0;

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


            String m = bank.get(index).getTitle();
            manager.updateDownloadedMagazines(
                    Integer.parseInt(m.substring(m.lastIndexOf(" ") + 1)),
                    file.toString());
            output.flush();
            output.close();
            input.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
        startActivity(getIntent());
        finish();

        return null;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {

        super.onProgressUpdate(values);
        progress.setProgress(values[0]);

    }

    @Override
    protected void onPostExecute(Long result) {

        super.onPostExecute(result);

        progress.setVisibility(View.INVISIBLE);



    }

}

Question:
How can i implement multiple download functionality so that progress bar shows progress of each download individually??

Answer 1

I have defined the image view and the progress bar as final and sending these references to the AsyncTask where the magazine downloading activity is going, on click of image view.
AsyncTask spawns multiple threads and that’s how progress of each download can be updated.Code:

   @Override
    public View getView(final int position, View convertView, ViewGroup arg2) {

        View grid;

        if (convertView == null) {
            grid = new View(context);
            grid = layoutInflater.inflate(item, null);

        } else {
            grid = (View) convertView;
        }

        final TextView title = (TextView) grid.findViewById(R.id.mgntitle);
        title.setText(bank.get(position).getTitle());
        final ImageView imageView = (ImageView) grid
                .findViewById(R.id.thumbnail);
        imageView.setImageResource(R.drawable.icon);
        final ProgressBar progress = (ProgressBar) grid
                .findViewById(R.id.progress);
        final ImageView downloadmark = (ImageView) grid
                .findViewById(R.id.downloadmark);
        String pdfLink = bank.get(position).getPdfLink();
        String filename = pdfLink.substring(pdfLink.lastIndexOf("/") + 1);
        final File targetDir = new File(fileLocation + filename);
        System.out.println("target file name " + targetDir);

        if (new File(fileLocation + filename).exists()) {
            if (!getPrefName(filename).equalsIgnoreCase("NA")) {
                downloadmark.setVisibility(View.VISIBLE);
            }
        }



        imageView.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                if (!targetDir.exists()) {
                        map.put(bank.get(position).getTitle(), progress);
                        new DoBackgroundTask(GridDisplayActivity.this, bank
                                .get(position).getPdfLink(), progress,
                                downloadmark, imageView, position)
                                .execute();


                }


            }

        });

        imageView.setImageBitmap(BitmapFactory.decodeByteArray(
                bank.get(position).getCoverPages(), 0, bank.get(position)
                        .getCoverPages().length));


        return grid;

    }