@Override
    public void destroy(final Collection<Pair<GeoPrimitive, Pair<Drawable, MarkerInterface>>> values) {

        for (Pair<GeoPrimitive, Pair<Drawable, MarkerInterface>> v : values) {
            remove(v.first, v.second);
        }
        flushMapChanges();

        map = null;
        mapLayers = null;
        markerLayerMap.clear();
        vectorLayerMap.clear();
        defaultMarkerSymbol = null;
    }
mimics {@link #removeItem(MarkerInterface)} but w/o calling 'populate'
main/src/main/java/cgeo/geocaching/unifiedmap/geoitemlayer/MapsforgeVtmGeoItemLayer.java