public synchronized void addDbAccessListener(DbAccessListener l) {
   if (l == null) return;
   if (dbAccessListeners == null) dbAccessListeners = new ArrayList<DbAccessListener>();
   if (!dbAccessListeners.contains(l)) dbAccessListeners.add(l);
 }
 public synchronized void removeDbAccessListener(DbAccessListener l) {
   if (dbAccessListeners != null && dbAccessListeners.contains(l)) dbAccessListeners.remove(l);
 }