GWT CellList; programmatical scrolling between elements options - gwt

Question

I would like to understand the options available to scrolling to a specific element in a CellList? Currently I have a 100 elements in the list and need to "jump" through the elements at the click of a button but can't seems to locate any methods on the celllist (or in the code) that provides this feature.
Any Ideas?
Many Thanks in advance,
Ian.
**EDIT
working code example below;
public class CellListTest implements EntryPoint {
private CellList<String> cellList;
private SingleSelectionModel<String> stringSingleSelectionModel;
/**
* This is the entry point method.
*/
public void onModuleLoad() {
cellList = new CellList<String>(new TextCell());
cellList.setRowData(buildStringList(200));
cellList.setKeyboardSelectionPolicy(HasKeyboardSelectionPolicy.KeyboardSelectionPolicy.BOUND_TO_SELECTION);
Button byTen = new Button("Jump Forward 10");
stringSingleSelectionModel = new SingleSelectionModel<String>();
cellList.setSelectionModel(stringSingleSelectionModel);
byTen.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
jumpForward(10);
}
});
byTen.setHeight("30px");
HTMLPanel htmlPanel = new HTMLPanel("");
VerticalPanel verticalPanel = new VerticalPanel();
cellList.setHeight("600px");
ScrollPanel scrollPanel = new ScrollPanel(cellList);
verticalPanel.add(byTen);
verticalPanel.add(scrollPanel);
htmlPanel.add(verticalPanel);
RootLayoutPanel.get().add(htmlPanel);
}
final Random random = new Random();
private List<String> buildStringList(int numberToCreate) {
final ArrayList<String> randomValues = new ArrayList<String>();
for (int i = 0; i < numberToCreate; i++) {
randomValues.add(String.valueOf(random.nextInt()));
}
return randomValues;
}
private int currentPosition = 0;
private void jumpForward(int toJump) {
Element rowElement = cellList.getRowElement(currentPosition += toJump);
rowElement.scrollIntoView();
}
}

Answer 1

I do not think CellList has a direct method for your purpose.
What you can do is use Element's scrollIntoView method. This method adjusts the scrollLeft and scrollTop properties of each scrollable element to ensure that the specified element is completely in view. In order to use that method you need to get the element containing the cell you want to show. One way to achive this is by using CellList public getRowElement(int indexOnPage).
I have not tryed it, but I believe the following code should work:
//Ensures cell 22 on page is shown
Element element = myCellList.getRowElement(22);
element.scrollIntoView();

Answer 2

Scrolling the element into view is one thing; changing the keyboard focus to a particular element is quite another. After much exploration, I have found that the best way to achieve that is to fire native events to simulate the user pressing keys.
private void hitKeyOnList(int keyCode) {
NativeEvent keyDownEvent = Document.get().createKeyDownEvent(
false, false, false, false, keyCode);
list.getElement().dispatchEvent(keyDownEvent);
}
In the above snippet, the list variable is a reference to a CellList.
So, to move the cursor to the end of the list, do this:
hitKeyOnList(KeyCodes.KEY_END);
to move the cursor to the next item down from the one that currently has keyboard focus:
hitKeyOnList(KeyCodes.KEY_DOWN);
This approach should work for all of these keys, which are handled by AbstractHasData:
KeyCodes.KEY_DOWN
KeyCodes.KEY_UP
KeyCodes.KEY_PAGEDOWN
KeyCodes.KEY_PAGEUP
KeyCodes.KEY_HOME
KeyCodes.KEY_END