如何在GWT中检测滚动面板是否仍在滚动？

import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.ui.ScrollPanel;
import com.google.gwt.user.client.ui.Widget;
import com.google.gwt.event.logical.shared.ScrollEvent;
import com.google.gwt.event.logical.shared.ScrollHandler;

public class ScrollPanelUtils {
  private static int previousScrollPosition = -1;

  public static boolean isScrolling(ScrollPanel scrollPanel) {
    Widget scrollPanelWidget = scrollPanel.getWidget();
    if (scrollPanelWidget != null) {
      DOM.sinkEvents(scrollPanelWidget.getElement(), DOM.getEventsSunk(scrollPanelWidget.getElement()) | DOM.getEventsSunk(DOM.getElementById(scrollPanel.getElement().getId())));
    }

    scrollPanel.addScrollHandler(new ScrollHandler() {
      @Override
      public void onScroll(ScrollEvent event) {
        int currentScrollPosition = scrollPanel.getVerticalScrollPosition();
        if (currentScrollPosition == previousScrollPosition) {
          // 滚动面板已经停止滚动
          // 在这里执行相应的操作
        } else {
          // 滚动面板仍在滚动
          // 在这里执行相应的操作
        }
        previousScrollPosition = currentScrollPosition;
      }
    });

    return scrollPanel.getMaximumVerticalScrollPosition() > 0;
  }
}