public synchronized void show(final K key) {
        final Pair<GeoItem, Boolean> value = itemMap.get(key);
        if (value != null && !value.second) {
            itemMap.put(key, new Pair<>(value.first, true));
            putToMap(key, value.first, null);
        }
    }
If an object for given key exists on the layer, it is made visible
main/src/main/java/cgeo/geocaching/unifiedmap/geoitemlayer/GeoItemLayer.java