Cannot resolve attribute 'treeDataDescriptor' for component type mx.controls.Tree.

Question

Hi,
I'm trying to compile an example from the documentation:
I have two files :
treeEx1.mxml
<?xml version="1.0" encoding="iso-8859-1"?>
<mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
creationComplete="initCollections()">
<mx:Script>
<![CDATA[
import mx.collections.*;
import mx.controls.treeClasses.*;
import customComp.MyCustomTreeDataDescriptor;
//Variables used to construct the ArrayCollection data
provider
//First top-level node and its children.
public var nestArray1:Object = [
{label:"item1", children: [
{label:"item1 child", children: [
{label:"item 1 child child", data:"child data"}
//Second top-level node and its children.
public var nestArray2:Object = [
{label:"item2", children: [
{label:"item2 child", children: [
{label:"item 2 child child", data:"child data"}
//Second top-level node and its children.
public var nestArray3:Object = [
{label:"item3", children: [
{label:"item3 child", children: [
{label:"item 3 child child", data:"child data"}
//Variable for the tree array.
public var treeArray:Object
//Variables for the three Array collections that correspond
to the
//top-level nodes.
public var col1:ArrayCollection;
public var col2:ArrayCollection;
public var col3:ArrayCollection;
//Variable for the ArrayCollection used as the Tree data
provider.
[Bindable]
public var ac:ArrayCollection;
//build the ac ArrayCollection from its parts.
public function initCollections():void{
// Wrap each top-level node in an ArrayCollection.
col1 = new ArrayCollection(nestArray1);
col2 = new ArrayCollection(nestArray2);
col3 = new ArrayCollection(nestArray3);
// Put the three top-level node ArrayCollections in the
treeArray.
treeArray = [
{label:"first thing", children: col1},
{label:"second thing", children: col2},
{label:"third thing", children: col3},
//Wrap the treeArray in an ArrayCollection.
ac = new ArrayCollection(treeArray);
// Adds a child node as the first child of the selected
node,
// if any. The default selectedNode is null, which causes
the
// data descriptor addChild method to add it as the first
child
// of the ac ArrayCollection.
public function clickAddChildren():void {
var newChild:Object = new Object();
newChild.label = "New Child";
newChild.children = new ArrayCollection();
tree.treeDataDescriptor.addChildAt(tree.selectedNode,
newChild, 0, ac);
]]>
</mx:Script>
<mx:Tree width="200" id="tree" dataProvider="{ac}"
treeDataDescriptor="{new MyCustomTreeDataDescriptor()}"/>
<mx:Button label="add children"
click="clickAddChildren()"/>
</mx:Application>
and
and MyCustomTreeDataDescriptor.as :
package customComp.MyCustomTreeDataDescriptor
import mx.collections.ICollectionView;
import mx.collections.IViewCursor;
import mx.events.TreeModelChangedEvent;
import mx.events.TreeModelChangedEventDetail;
import mx.controls.treeClasses.*;
public class MyCustomTreeDataDescriptor implements
ITreeDataDescriptor
// The getChildren method requires the node to be an Object
// with a children field.
// If the field contains an ArrayCollection, it returns the
field
// Otherwise, it wraps the field in an ArrayCollection.
public function getChildren(node:Object,
model:Object=null):ICollectionView
try
if (node is Object)
if(node.children is ArrayCollection){
return node.children;
}else{
return new ArrayCollection(node.children);
catch (e:Error)
trace("[Descriptor] exception checking for getChildren");
return null;
// The isBranch method simply returns true if the node is an
// Object with a children field.
// It does not support empty branches, but does support null
children
// fields.
public function isBranch(node:Object,
model:Object=null):Boolean
try
if (node is Object)
if (node.children != null)
return true;
catch (e:Error)
trace("[Descriptor] exception checking for isBranch");
return false;
// The getData method simply returns the node as an Object.
public function getData(node:Object,
model:Object=null):Object
try
return Object(node);
catch (e:Error)
return null;
// The addChildAt method does the following:
// If the node parameter is null or undefined, inserts
// the child parameter as the first child of the model
parameter.
// If the node parameter is an Object and has a children
field,
// adds the child parameter to it at the index parameter
location.
// It does not add a child to a terminal node if it does not
have
// a children field.
public function addChildAt(node:Object, child:Object,
index:int, model:Object=null):Boolean
var event:TreeModelChangedEvent = new
TreeModelChangedEvent("modelChanged", false, false,
TreeModelChangedEventDetail.ADD_NODE, child, node, index);
if (!node)
var iterator:IViewCursor = model.createCursor();
iterator.seek(CursorBookmark.FIRST, index);
iterator.insert(child);
else if (node is Object)
if (node.children != null)
if(node.children is ArrayCollection) {
node.children.addItemAt(child, index);
if (model){
model.dispatchEvent(event);
model.itemUpdated(node);
return true;
else {
node.children.splice(index, 0, child);
if (model)
model.dispatchEvent(event);
return true;
return false;
I have read the docs and looked through some example on this
form but I still can't figure it out .
Thanks
The code above is from:
http://127.0.0.1:56812/help/topic/com.adobe.flexbuilder.help/html/Part2_DevApps.html
Using hierarchical data providers

Answer 1

I hav echnaged it and now I get :
A file found in an source-path must have the same package
structure 'customComp', as the definition's package,
'customComp.MyCustomTreeDataDescriptor'.
I tried different variations but nothing seems to work. I
have the following folder structure:
\Lessons
\customComp
.MyCustomTreeDataDescriptor.as
treeEx1.mxml
Thanks