public static <GT, TT> Func5<GT, ItemGroup<TT, GT>, Context, View, ViewGroup, View> constructGroupDisplayViewMapper(final Function<ItemGroup<TT, GT>, TextParam> displayGroupTextMapper) {
        return (group, itemGroup, context, view, parent) -> {
            final TextView tv = view instanceof TextView ? (TextView) view : ViewUtils.createTextItem(context, R.style.text_default, TextParam.text(""));
            final TextParam tp = displayGroupTextMapper == null || itemGroup == null ? TextParam.text(String.valueOf(itemGroup)) : displayGroupTextMapper.apply(itemGroup);
            if (tp == null) {
                tv.setText("--");
            } else {
                tp.applyTo(tv);
            }
            return tv;
        };
    }
Sets a display providing the text visualization for an item
main/src/main/java/cgeo/geocaching/ui/SimpleItemListModel.java