sample.java

// in the performFiltering method which runs on a background thread:
@Override
protected FilterResults performFiltering(CharSequence constraint) {
  FilterResults filterResults = new FilterResults();
  ArrayList<String> queryResults;
  if (constraint != null || constraint.length() == 0) {
    queryResults = autocomplete(constraint);
  } else {
    queryResults = new ArrayList<String>(); // empty list/no suggestions showing ig there's no constraint
  }
  filterResults.values = queryResults;
  filterResults.count = queryResults.size();  
}

private List<String> autocomplete(String input) {
  // don't use the here the resultList List on which the adapter is based!
  // some custom code to get items from http connection          
  ArrayList<String> queryResults = new ArrayList<String>(); // new list
  queryResults.add("Some String");
  return queryResults;
}

@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
  resultList = (ArrayList<String>)results.values;
  if (results.count > 0) {
    notifyDataSetChanged();
  } else {
    notifyDataSetInvalidated();
  }
}