code: protected Filter getFilter() {
          switch (mAutoCompleteMode){
              case AUTOCOMPLETE_MODE_SINGLE:
                  return ((InternalAutoCompleteTextView)mInputView).superGetFilter();
              case AUTOCOMPLETE_MODE_MULTI:
                  return ((InternalMultiAutoCompleteTextView)mInputView).superGetFilter();
              default:
                  return null;
          }
      }
docs: Returns the Filter obtained from {@link Filterable#getFilter},
  or <code>null</code> if {@link #setAdapter} was not called with
  a Filterable.