private void pruneSelected() {
        if (choiceMode != ChoiceMode.MULTI_CHECKBOX && selectedItems.size() > 1) {
            final T remaining = CommonUtils.first(selectedItems);
            selectedItems.clear();
            selectedItems.add(remaining);
        }
    }
Sets the (visual) choice mode to use. For single-choice modes, the model ensures that max.
 one item is selected at any time.
main/src/main/java/cgeo/geocaching/ui/SimpleItemListModel.java