Android: AsyncTask ProgressDialog will not open in ActivityGroup

I am trying to have a a progress dialog open when polling my server. The class is an ActivityGroup because it is nested within a tab bar. To keep the view within the frame, the ActivityGroup is needed. Here is the declaration of my ActivityGroup class:

   public class CheckInActivity extends ActivityGroup{
        ...
        public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.checkin);
            new LocationControl().execute(this);

Now my AsyncTask class is within the same CheckInActivityClass as such:

private class LocationControl extends AsyncTask<Context, Void, Void>
    {
        private final ProgressDialog dialog = new ProgressDialog(CheckInActivity.this);

        protected void onPreExecute()
        {
            this.dialog.setMessage("Determining your location...");
            this.dialog.show();
        }

When I run the given app it throughs an error relating to WindowManager$BadTokenException. Stating the it cannot start the window with an unknown token. I tried making a sample app that is just a regular Activity(not ActivityGroup) and it worked just fine.

Does anyone know how to modify this to make it work, or a work around that will allow the progress bar to be nested within the tab bar? Any help is greatly appreciated.