Remove () or clear () from SharedPreferences doesn't work

I am trying to clear my Arraylist using SharedPreferences, but the code below does not work:

public void btnLimparPref(View v){

         SharedPreferences preferences = getSharedPreferences("listaPedidos", MODE_WORLD_WRITEABLE);
         preferences.edit().clear().commit();
     }

      

        
        
        
      

    

This code represents an Activity, and the Arraylist is saved in a fragment by this code:

void criaArray(String nomeProd, String descrProd) {


        HashMap<String, String> map3 = new HashMap<String, String>();           
        map3.put(TAG_NM, nomeProd);
        map3.put(TAG_DS, descrProd);

        listaPedidos.add(map3);    

            //getListView();
            ((BaseAdapter) adapter2).notifyDataSetChanged();

            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity().getApplicationContext());
            Editor editor = prefs.edit();
            try {
                editor.putString("listaPedidos", ObjectSerializer.serialize(listaPedidos));
            } catch (IOException e) {
                e.printStackTrace();
            }
            editor.commit();

    }   

      

        
        
        
      

    

Any ideas? Thanks in advance!