在ProgressWheel中设置下载文件的进度

Question

我有一个列表视图。当用户选择列表视图中的项目时，我打开DetailActivity，用户可以在该活动中下载文件，并使用ProgressWheel显示用户下载百分比。

我的问题是当用户关闭活动然后返回活动时，ProgressWheel不再更新。 这是我的代码:(我使用AsynchTask下载文件）

/**
 * Background Async Task to download file
 * */
class DownloadTask extends AsyncTask<String, String, Boolean> {
    /**
     * Downloading file in background thread
     * */
    @Override
    protected Boolean doInBackground(String... params) {
        try {
            URL url = null;
            try {
                String link = params[0];
                fileExtention = getFileExtention(link);
                url = new URL(link);
            } catch (Exception e) {
                e.printStackTrace();
                return false;
            }

            HttpURLConnection connection = (HttpURLConnection) url
                    .openConnection();
            // set some parameters for httpUrlConnection
            connection.setConnectTimeout(JSONConstants.CONNECTION_TIMEOUT);
            connection.setReadTimeout(JSONConstants.READ_TIMEOUT);
            connection.connect(); // Connection Complete here.!
            // Get from Server and Catch In Input Stream Object.
            InputStream inputStream = connection.getInputStream();
            int lenghtOfFile = connection.getContentLength();

            String PATH = Environment.getExternalStorageDirectory()
                    + "/download/";
            File file = new File(PATH); 
            if (!file.exists()) {
                file.mkdirs();
            }
            File outputFile = new File(file, "fileTitle"
                    + ".mp3" );
            FileOutputStream fileOutputStream = new FileOutputStream(
                    outputFile);

            byte[] buffer = new byte[4096];
            int length = 0;
            long total = 0;
            while ((length = inputStream.read(buffer)) != -1) {
                total += length;
                // publishing the progress....
                // After this onProgressUpdate will be called
                if (lenghtOfFile > 0)
                    publishProgress(""
                            + (int) ((total * 100) / lenghtOfFile));

                // Write In FileOutputStream.
                fileOutputStream.write(buffer, 0, length);
            }
            fileOutputStream.flush();
            fileOutputStream.close();
            inputStream.close();

        }  catch (Exception e) {    
            e.printStackTrace();
            return false;
        }
        return true;
    }

    private void publishProgress(String percent) {
        // Sets the progress indicator to a max value, the
        // current completion percentage, and "determinate"
        // state
        downloadProgressWheel.setProgress(Integer.valueOf(percent));

    }

当用户返回其相关活动时，如何设置我的ProgressWheel仍然更新。