public static ListPreference getPreference(final Context context) {
        final ListPreference themeVariants = new ListPreference(context);
        themeVariants.setTitle(R.string.vtm_theme_variant);
        themeVariants.setSummary(getDefaultVariant().name());
        themeVariants.setKey(context.getString(R.string.pref_vtm_default));
        final CharSequence[] variants = new CharSequence[VtmThemes.values().length];
        int i = 0;
        for (VtmThemes vtmTheme : VtmThemes.values()) {
            variants[i] = vtmTheme.name();
            i++;
        }
        themeVariants.setEntries(variants);
        themeVariants.setEntryValues(variants);
        themeVariants.setOnPreferenceChangeListener((preference, newValue) -> {
            themeVariants.setSummary(newValue.toString());
            return true;
        });
        themeVariants.setDefaultValue(VtmThemes.OSMARENDER.name());
        themeVariants.setIconSpaceReserved(false);
        return themeVariants;
    }
returns ListPreference to select one of the built-in themes from
main/src/main/java/cgeo/geocaching/unifiedmap/mapsforgevtm/VtmThemes.java