public static void setSelectedMapRenderTheme(final String customRenderThemeFile) {
        putString(R.string.pref_renderthemefile, customRenderThemeFile);
    }
Shall SOLELY be used by {@link cgeo.geocaching.maps.mapsforge.v6.RenderThemeHelper}!
main/src/main/java/cgeo/geocaching/settings/Settings.java