public synchronized void hideAll() {
        for (Map.Entry<K, Pair<GeoItem, Boolean>> entry : this.itemMap.entrySet()) {
            if (entry.getValue().second) {
                entry.setValue(new Pair<>(entry.getValue().first, false));
                removeFromMap(entry.getKey(), entry.getValue().first);
            }
        }
    }
All objects in this layer are made invisible
main/src/main/java/cgeo/geocaching/unifiedmap/geoitemlayer/GeoItemLayer.java