问在AsyncTask中调用execute()

EN

loadSomeStuff slb = new SamsungLB().new loadSomeStuff();
                        slb.execute(USA.this.getSherlockActivity());

public void execute(SherlockFragmentActivity sherlockActivity) {
            // TODO Auto-generated method stub
            this.ctx = sherlockActivity;
        }

if (ctx == null) {
                System.out.print("null");
            }

public class loadSomeStuff extends AsyncTask<String, Integer, String> {

ProgressDialog dialog;
Context ctx;

protected void onPreExecute() {
    dialog = new ProgressDialog(ctx);
    dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    dialog.setCancelable(false);
    dialog.setIndeterminate(false);
    dialog.setMessage(getResources().getString(R.string.searching));
    dialog.show();
}

@Override
protected String doInBackground(String... params) {
    // TODO Auto-generated method stub
    //fillinglistview//
    }
    if (ctx == null) {
        System.out.print("null");
    }
    return null;
}

protected void onProgressUpdate(Integer... progress) {

}

protected void onPostExecute(String result) {
    listview.setAdapter(new MyListAdapterSamsung(getActivity(),
            beanClass));
    if (beanClass.isEmpty()) {
        Toast.makeText(getSherlockActivity(), "No Connection",
                Toast.LENGTH_LONG).show();
    }

}

public void execute(SherlockFragmentActivity sherlockActivity) {
    // TODO Auto-generated method stub
    this.ctx = sherlockActivity;
}
}