Spinner in Android doesn't show its selected item

It successfully manage to connect to the db, retrieve the data, and show them in the dropdown menu. But when i select an item in the spinner, it doesn't show in the "box".

   ArrayList<String> communities = new ArrayList<String> ();
  Spinner mySpinner = (Spinner) findViewById(R.id.lstCommunity);
    ArrayAdapter adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, communities); 

    mySpinner.setAdapter(adapter);
    popolaSpinner(communities,adapter);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

popolaSpinner is the function that takes the data from the DB

I also used

  protected void onPostExecute() {
 this.getArrayAdapterUsed().notifyDataSetChanged();
 }