title: AlertDialog setmessage not working inside Asynctask
body: <p>Below is my code my trying to display my progress in Asyntask via onProgressUpdate method but it aint showing in the alert diaalog. Only the initial message is shown.</p>
  
  <pre><code> class DownloadFileFromURL extends AsyncTask&lt;String, String, String&gt; {
  
          private AlertDialog.Builder alert;
          private int progress = 0;
          /**
           * Before starting background thread Show Progress Bar Dialog
           */
          @Override
          protected void onPreExecute() {
              super.onPreExecute();
              alert = new AlertDialog.Builder(context);
              alert.setTitle("Downloading..");
              alert.setMessage("1");
              alert.setCancelable(false);
              alert.show();
          }
  
          /**
           * Downloading file in background thread
           */
          @Override
          protected String doInBackground(String... f_url) {
              int count;
              try {
                  URL url = new URL(f_url[0]);
                  URLConnection conection = url.openConnection();
                  conection.connect();
  
                  // this will be useful so that you can show a tipical 0-100%
                  // progress bar
                  int lenghtOfFile = conection.getContentLength();
  
                  // download the file
                  InputStream input = new BufferedInputStream(url.openStream(),
                          8192);
  
                  // Output stream
                  OutputStream output = new FileOutputStream(file);
  
                  byte data[] = new byte[1024];
  
                  long total = 0;
  
                  while ((count = input.read(data)) != -1) {
                      total += count;
                      // publishing the progress....
                      // After this onProgressUpdate will be called
                      publishProgress("" + (int) ((total * 100) / lenghtOfFile));
  
                      // writing data to file
                      output.write(data, 0, count);
                  }
  
                  // flushing output
                  output.flush();
  
                  // closing streams
                  output.close();
                  input.close();
  
              } catch (Exception e) {
                  Log.e("Error: ", e.getMessage());
              }
  
              return null;
          }
  
          /**
           * Updating progress bar
           */
          @Override
          protected void onProgressUpdate(String... progress) {
              Log.d("Myapp","progress :"+progress[0]);
              alert.setMessage(""+progress[0]);
          }
  
          /**
           * After completing background task Dismiss the progress dialog
           **/
          @Override
          protected void onPostExecute(String file_url) {
              // dismiss the dialog after the file was downloaded
  }
  }
  </code></pre>
  
  <p>As i have also written a log to show progress update in onProgressUpdate, the log is printed but the alert.setMessage in onProgressUpdate seems not set the message to my alert dialog.</p>