notifyDataSetChanged in a listfragment does nothing

I have a listfragment with an adapter define like this :

ArrayAdapter<String> aa;
    ArrayList<String> arrayList = new ArrayList<String>();

aa = new ArrayAdapter<String>(getActivity(),
                android.R.layout.simple_list_item_1,  arrayList);
        setListAdapter(aa);

I 'm using this to add item to my list from an sqlite database

arrayList.add

the problem is that notify data has change does nothing (i m deleting element from the sqlite so i need to refresh the content of the arraylist)

i'm doing this :

aa.notifyDataSetChanged();