GWT 2.1 Data Presentation Widgets without paging

Question

I am trying to build a table with large dataset and would like to avoid paging. (I would like to do something similar to Yahoo Mail grid which retrieves data after the grid is drawn. I think initially the first 100 mails are retrieved and then mail is only retrieved after the user scrolls down)

The example of the data presentation widget I have seen include paging. Is it possible to do what I want?

edit: You could also call this an infinite scroll table

Answer 1

Yes, it is possible. There used to be an example of that called DynaGrid here but that link is dead now. I haven't been able to find it anywhere else (note: that's not the same as the DynaGrid on SourceForge). You might be able to contact the author, Reinier Zwitserloot, to inquire about getting a copy of his DynaGrid. You could also search the GWT Group and if you don't find anything, post there asking if anyone else knows where to find it.

Answer 2

Ext Gwt (AKA GXT) has an implementation of a "Live Grid" that supports this functionality (see http://www.sencha.com/examples/explorer.html#livegrid). The code is GPL although you can buy a license to use this in commercial applications.

Answer 3

Dean already mentioned Ext GWT but I'd like to suggest SmartGWT's implementation as well.

Answer 4

There are an exemple of this in the GWT Showcase

/**
 * A scrolling pager that automatically increases the range every time the
 * scroll bar reaches the bottom.
 */
public class ShowMorePagerPanel extends AbstractPager {

  /**
   * The default increment size.
   */
  private static final int DEFAULT_INCREMENT = 20;

  /**
   * The increment size.
   */
  private int incrementSize = DEFAULT_INCREMENT;

  /**
   * The last scroll position.
   */
  private int lastScrollPos = 0;

  /**
   * The scrollable panel.
   */
  private final ScrollPanel scrollable = new ScrollPanel();

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

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

  /**
   * Get the number of rows by which the range is increased when the scrollbar
   * reaches the bottom.
   *
   * @return the increment size
   */
  public int getIncrementSize() {
    return incrementSize;
  }

  @Override
  public void setDisplay(HasRows display) {
    assert display instanceof Widget : "display must extend Widget";
    scrollable.setWidget((Widget) display);
    super.setDisplay(display);
  }

  /**
   * Set the number of rows by which the range is increased when the scrollbar
   * reaches the bottom.
   *
   * @param incrementSize the incremental number of rows
   */
  public void setIncrementSize(int incrementSize) {
    this.incrementSize = incrementSize;
  }

  @Override
  protected void onRangeOrRowCountChanged() {
  }
}