Get item by index in a tree control

Question

I'm doing a drag and drop operation on a tree using some help from Adobe's quick Starts: http://www.adobe.com/devnet/flex/quickstart/working_with_tree/

The code suggested is roughly this:

var dropTarget:Tree = Tree(evt.currentTarget);
var i:int = dropTarget.calculateDropIndex(evt);
myTree.selectedIndex = i;
var node:XML = myTree.selectedItem as XML;
var drugXML:XML = XML(Tree(evt.dragInitiator).selectedItem);
if(node.localName() != drugXML.localName()){
    DragManager.showFeedback(DragManager.NONE);
    return;
}else{
    DragManager.showFeedback(DragManager.COPY);
}

This is all well and good, but I don't like the way it is selecting(highlighting) each item in the tree I'm dropping on, it's less clear where the item is going to drop. I want to implement this without the selection but there doesn't seem to be a way to get the XML of the node using just the index. I would like something like this:

var dropTarget:Tree = Tree(evt.currentTarget);
var i:int = dropTarget.calculateDropIndex(evt);

var node:XML = myTree.itemAt(i) as XML; 
//AFAIK itemAt(i) or anything like it does not exist

var drugXML:XML = XML(Tree(evt.dragInitiator).selectedItem);
if(node.localName() != drugXML.localName()){
    DragManager.showFeedback(DragManager.NONE);
    return;
}else{
    DragManager.showFeedback(DragManager.COPY);
}

So does anyone know what function is, or what I can do to extend the tree to have a function, like "itemAt(i)"

Thanks ~Mike

EDIT: I forgot to post that my current workaround is setting the selectedIndex = -1 after I get my node:XML. I'm afraid that if something bogs on the processor the user may see it select then deselect.

Answer 1

If your dataProvider is explicitly or implicitly a collection (see the linked docs for conversion rules), you should be able to use getItemAt to resolve the index.

It appears that an XML provider will be converted implicitly:

var tree:Tree = ...;
var data:XML = ...;
tree.dataProvider = data; // could just as well be from MXML

var provider:ICollectionView = tree.collection; // tree converted it for us
trace(provider.getItemAt(index));

If you have something other than the convertible types (XML, Array, etc.), you might consider wrapping your dataProvider in an XMLListCollection or what have you to gain access to that method.

---

The above is aiming in the right direction but missing.

Turns out you don't want the dataProvider since Tree overrides that; you want the collection property (protected). So you could override Tree and provide an indexToItem method to go with the thisToThat methods already present in Tree.

Answer 2

Much simpler, though there may be gotchas:

var index:int = ...
var renderer:IListItemRenderer = tree.indexToItemRenderer(index);
var item:Object = renderer.data;

This won't work if the index is offscreen (since there might not be an active itemRenderer); shouldn't be an issue for drag and drop.