box.addDomHandler(new PDropHandler() {
@Override
public void onDrop(final PDropEvent event) {
box.removeStyleName("dragenter");
final PWidget source = event.getDragSource();
if (source != null && source != box) {
final int dropIndex = boxContainer.getWidgetIndex(box);
boxContainer.remove(source);
boxContainer.insert(source, dropIndex);