* <p>Note: you can invoke this method only in an event listener.
* @param type the {@link MapDataEvent} type
* @param items the items to be processed
*/
protected void fireEvent(int type, Collection items) {
final MapDataEvent evt = new MapDataEvent(this, type, items);
for (Iterator it = _listeners.iterator(); it.hasNext();)
((MapDataListener)it.next()).onChange(evt);
}