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);
            }
        }
    });
}