code: private void adaptButtonBarDividerVisibility() {
          if (buttonBarDivider != null) {
              buttonBarDivider.setVisibility(showButtonBarDivider ? View.VISIBLE : View.GONE);
              buttonBarDivider.setVisibleByDefault(showButtonBarDivider);
          }
      }
docs: Adapts the visibility of the divider, which is shown above the dialog's buttons.