@Override
public void undo() throws CannotUndoException {
super.undo();
upperModel.remove(moved);
moved.setParent(lowerModel.getOwner());
lowerModel.add(moved);
}
@Override
public void redo() throws CannotRedoException {
super.redo();
lowerModel.remove(moved);
GroupLayer gl = lowerModel.getOwner();
int i = upperModel.list().indexOf(gl);
moved.setParent(upperModel.getOwner());
upperModel.add(i, moved);
}