public TextSpinner<T> setDisplayMapper(@Nullable final Func1<T, TextParam> displayMapper) {
        this.displayMapper = displayMapper;
        recalculateDisplayValues();
        return this;
    }
(Re)Sets the display mapper, which is used to get a visible representation for all list values.
If not set, values are displayed using {@link String#valueOf(Object)}.
Mapper will never be called for null values.
main/src/main/java/cgeo/geocaching/ui/TextSpinner.java