为什么片段内的ListView没有更新？

Question

我在片段中有一个ListView：

public class EditorFragment extends SherlockFragment {
  private EditText editor = null;
  private ListView lv = null;
  private EditText et = null;
  private File root = null;
  private String[] nomi={"test1","test2"};
  private ArrayAdapter<String> aa;

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup parent,
                                                 Bundle savedInstanceState) {
    setHasOptionsMenu(true);

    View result = inflater.inflate(R.layout.editor, parent, false);

    editor = (EditText) result.findViewById(R.id.editor);
    lv = (ListView) result.findViewById(R.id.list);
    root = getActivity().getExternalFilesDir(null);
    aa = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, nomi );
    lv.setAdapter(aa);
    return (result);
}

当用户单击ActionBar上的按钮时，将调用以下方法。

由于它包含notifyDataSetChanged()，我希望ListView能够刷新，但这不会发生......

private File getTarget() {
  int i = 0;
  if(et!=null)
        FILENAME=et.getText().toString();
  if(root.list().length!=0) {
        nomi= new String[(int) root.length()];
        nomi=root.list();
  };
  aa.notifyDataSetChanged();
  return (new File(root,FILENAME));
}

感谢您的帮助！