AsyncTask onPreExecute progressdialog

У меня есть AsyncTask, когда функция onPreExecute выполняется, это дает мне исключение

** java.lang.IllegalStateException: просмотр com.android.internal.policy.impl.PhoneWindow$DecorView@44ea0e20 уже добавлен в окно manager. **

при вызове метода show () progressDialog.

Моя активность

public class TopNewsActivity extends ListActivity {

public static final String LOG_TAG = "Infra";
private ProgressDialog progressDialog;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.listplaceholder);
    new BackgroundAsyncTask().execute();
}

public class BackgroundAsyncTask extends AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressDialog = new ProgressDialog(TopNewsActivity.this);
        progressDialog.setCancelable(true);
        progressDialog.setMessage("Loading...");
        progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        progressDialog.setProgress(0);
        progressDialog.show();
    }

    @Override
    protected ArrayList<HashMap<String, String>> doInBackground(String... paths) {
        ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

        String xml = XMLfunctions.getTopNewsXML();
        Document doc = XMLfunctions.XMLfromString(xml);

        int numResults = XMLfunctions.numResults(doc);
        Log.d(LOG_TAG, "Number of Results: " + numResults);
        if ((numResults <= 0)) {
            Toast.makeText(TopNewsActivity.this, "No Result Found",Toast.LENGTH_LONG).show();
            finish();
        }

        NodeList nodes = doc.getElementsByTagName("result");

        for (int i = 0; i < nodes.getLength(); i++) {
            HashMap<String, String> map = new HashMap<String, String>();

            Element e = (Element) nodes.item(i);
            map.put("id", XMLfunctions.getValue(e, "id"));
            map.put("title", XMLfunctions.getValue(e, "title"));
            mylist.add(map);
        }
        return mylist;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
    }

    protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
        ListAdapter adapter = new SimpleAdapter(TopNewsActivity.this, result, R.layout.list_item, new String[] { "title" }, new int[] { R.id.item_title });
        setListAdapter(adapter);
        progressDialog.dismiss();

        final ListView lv = getListView();

        lv.setTextFilterEnabled(true);  
        lv.setOnItemClickListener(new OnItemClickListener() {
            @SuppressWarnings("unchecked")
            @Override
            public void onItemClick(AdapterView<?> a, View view, final int position, long id) {

                    HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position);

                    Intent i = new Intent(TopNewsActivity.this, NewsDetails.class);
                    i.putExtra("content_id", o.get("id"));
                    i.putExtra("title", o.get("title"));
                    i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

                    View v = TopNewsGroup.group.getLocalActivityManager().startActivity("ShowNews", i).getDecorView();

                    // Again, replace the view
                    TopNewsGroup.group.setContentView(v);

            }
        });

    }

}

public class MySimpleAdapter extends SimpleAdapter {
     public MySimpleAdapter(Context context, List<? extends Map<String, ?>> data, int resource, String[] from, int[] to) {
        super(context, data, resource, from, to);
        // TODO Auto-generated constructor stub
}

}
}

Помогите !!!!!