GWT CellTree scroll to arbitrary node

Question

i'm coding some kind of objects browser, organized with folders. When user seslects some folder in the list i have to expand an appropriate node in a tree. I've implemented tree expand, element selection in tree, BUT expand might happen at a part of tree that is out of visible area (CellTree is on a ScrollPane). So, i do have an instace of TreeNode - how can i programmatically scroll to make it visible?

Answer 1

It's not possible with the current API, but what you can try, and I haven't tested this, but should be easy:

1. For each object in your tree render and invisible tag, identifying this object, like an <input type="hidden" id="yourObjectId"/>
2. Make sure you have a SelectionModel when setting up your NodeInfo etc.
3. When you know what object you want to scroll to, call yourSelectionModel.setSelected(object,true);. That should expand the tree and display your selected object.
4. At this stage what you want to do is:

Element cellTreeElement = yourCellTree.getElement();
NodeList<Element> objectIds = cellTreeElement.getElementsByTagName("input");
for ( int i=0;i<elementsByTagName.getLength();i++ )
{
   Element e = objectIds .getItem( i );
   if (e.getId().equals( yourObjectId ) {
     e.scrollIntoView();
   }
}

Pretty sure this should work just fine.

Answer 2

another version (if you want to move the element to the top of the CellTree):

    Element cellTreeElement = yourCellTree.getElement();
    NodeList<Element> objectIds = cellTreeElement.getElementsByTagName("input");
    for (int j = 0; j < objectIds.getLength(); j++) {
        Element e = objectIds.getItem(j);
        if (e.getId().equals("r" + iDistrictID)) {
            yourCellTree.getElement().getParentElement().getParentElement().setScrollTop(e.getParentElement().getParentElement().getOffsetTop());
        }
    }