@Override protected boolean createKeys(List<DataObject> keys) { List<DataObject> files = new ArrayList<DataObject>(); for (DataObject f : folder.getChildren()) { if (!filter.acceptDataObject(f)) { continue; f.addPropertyChangeListener(WeakListeners.propertyChange(this, f)); for (DataObject kid : ((DataFolder) f).getChildren()) { if (!filter.acceptDataObject(kid)) { continue;