/* sets or hides fields depending on which tab is shown */
  public void setVisibleComponents(nonHumanMgt.SelType sType) {
    boolean catTab = (sType == nonHumanMgt.SelType.category);

    // these only appear on the resources tab
    cbbCategory.setVisible(!catTab);
    lblSubCategory.setVisible(!catTab);
    cbbSubCategory.setVisible(!catTab);

    // these only appear on the categories tab
    lblMembers.setVisible(catTab);
    cbbMembers.setVisible(catTab);
    lbxSubCatItems.setVisible(catTab);
    btnAddSubCat.setVisible(catTab);
    btnRemoveSubCat.setVisible(catTab);

    // nullify lists
    if (catTab) {
      cbbCategory.setItems(null);
      cbbSubCategory.setItems(null);
    } else lbxSubCatItems.setItems(null);
  }