private void fillViewHolder(final ItemHolder holder, final IFilterViewHolder<?> filterViewHolder) {
            if (filterViewHolder == null) {
                return;
            }
            holder.setFilterViewHolder(filterViewHolder);
            setTheme();
        }
Show a filter selection using an {@code ExpandableListView}.
main/src/main/java/cgeo/geocaching/filters/gui/GeocacheFilterActivity.java