Progress is not shown when I navigate to another activity and return to same activity but doinbackground process is running
<p>Let me explain issue:
1. I have a activity inside my app which is contains do in background process for  perticuler task.
2. Inside pre execute process i set progress is visible on the top header of activity and inside post execute i set its gone.
3. But when i navigate to another activity and return to same activity,my progress is not visible but background process still running.<br>
  how can i solve this problem? </p>

<p><a href="http://i.stack.imgur.com/9Z02N.png" rel="nofollow">I notify the progress inside black circle</a>
  Below is my code :</p>

<pre><code>@Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();           
        progress.setVisibility(View.VISIBLE);   
        //showDialog();
    }
    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub
        upload(_file,_dir,this);
        return null;
    }
            @Override
    protected void onPostExecute(Void result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        //dismissDialog();
        uploadingCompleted(_uploadResult,_file);
        progress.setVisibility(View.GONE);

    }
</code></pre>