Spark List组件滚动条加事件使datalist数据发生变化

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/05/31/detecting-when-the-vertical-scroll-bar-is-scrolled-on-a-spark-list-control-in-flex-4/ -->
<s:Application name="Spark_List_scroller_verticalScrollBar_change_test"
      xmlns:fx="http://ns.adobe.com/mxml/2009"
      xmlns:s="library://ns.adobe.com/flex/spark"
      xmlns:mx="library://ns.adobe.com/flex/mx">
 
 <fx:Script>
  <![CDATA[
   import spark.components.VScrollBar;
   
   private function init():void {
    list.scroller.verticalScrollBar.addEventListener(Event.CHANGE, list_verticalScrollBar_change);
   }
   
   private function list_verticalScrollBar_change(evt:Event):void {
    var vsb:VScrollBar = evt.currentTarget as VScrollBar;
    var obj:Object = {};
    obj.type = evt.type;
    obj.val = vsb.value;
    obj.max = vsb.maximum;
    arrColl.addItem(obj);
    callLater(dgScroll);
   }
   
   private function dgScroll():void {
    dataGrid.verticalScrollPosition = dataGrid.maxVerticalScrollPosition;
   }
  ]]>
 </fx:Script>
 
 <fx:Declarations>
  <mx:ArrayCollection id="arrColl" />
 </fx:Declarations>
 
 <s:HGroup horizontalCenter="0" verticalCenter="0">
  <s:List id="list"
    creationComplete="init();">
   <s:layout>
    <s:VerticalLayout gap="0"
          horizontalAlign="contentJustify"
          requestedRowCount="4" />
   </s:layout>
   <s:dataProvider>
    <s:ArrayList>
     <fx:String>The</fx:String>
     <fx:String>Quick</fx:String>
     <fx:String>Brown</fx:String>
     <fx:String>Fox</fx:String>
     <fx:String>Jumps</fx:String>
     <fx:String>Over</fx:String>
     <fx:String>The</fx:String>
     <fx:String>Lazy</fx:String>
     <fx:String>Dog</fx:String>
    </s:ArrayList>
   </s:dataProvider>
  </s:List>
  <mx:DataGrid id="dataGrid"
      dataProvider="{arrColl}"
      width="200"
      verticalScrollPolicy="on">
   <mx:columns>
    <mx:DataGridColumn dataField="type" />
    <mx:DataGridColumn dataField="val" />
    <mx:DataGridColumn dataField="max" />
   </mx:columns>
  </mx:DataGrid>
 </s:HGroup>
 
</s:Application>