ShowMorePagerPanel.java 文件源码

/**
 * Construct a new {@link ShowMorePagerPanel}.
 */
public ShowMorePagerPanel() {
  initWidget(scrollable);

  // Do not let the scrollable take tab focus.
  scrollable.getElement().setTabIndex(-1);

  // Handle scroll events.
  scrollable.addScrollHandler(new ScrollHandler() {
    public void onScroll(ScrollEvent event) {
      // If scrolling up, ignore the event.
      int oldScrollPos = lastScrollPos;
      lastScrollPos = scrollable.getVerticalScrollPosition();
      if (oldScrollPos >= lastScrollPos) {
        return;
      }

      HasRows display = getDisplay();
      if (display == null) {
        return;
      }
      int maxScrollTop = scrollable.getWidget().getOffsetHeight()
          - scrollable.getOffsetHeight();
      if (lastScrollPos >= maxScrollTop) {
        // We are near the end, so increase the page size.
        int newPageSize = Math.min(
            display.getVisibleRange().getLength() + incrementSize,
            display.getRowCount());
        display.setVisibleRange(0, newPageSize);
      }
    }
  });
}