FLEX合并数组

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
<mx:Script><!--[CDATA[import mx.collections.ArrayCollection;
public var a1:ArrayCollection = new ArrayCollection ([{ Region:"Region1",Territory:"Territory1",Territory_Rep:"Territory_Rep1",Actual:11,Estimate:111}]);
public var a2:ArrayCollection = new ArrayCollection ([{ Region:"Region2",Territory:"Territory2",Territory_Rep:"Territory_Rep2",Actual:22,Estimate:222}]);
public var a3:ArrayCollection = new ArrayCollection ([{ Region:"Region3",Territory:"Territory3",Territory_Rep:"Territory_Rep3",Actual:33,Estimate:333}]);
public var a4:ArrayCollection = new ArrayCollection ([{ Region:"Region4",Territory:"Territory4",Territory_Rep:"Territory_Rep4",Actual:44,Estimate:444}]);
public var a5:ArrayCollection = new ArrayCollection ([{ Region:"Region5",Territory:"Territory5",Territory_Rep:"Territory_Rep5",Actual:55,Estimate:555}]);
public var dpFlat:ArrayCollection=new ArrayCollection(a1.toArray().concat(a2.toArray().concat(a3.toArray()).concat(a4.toArray()).concat(a5.toArray())))
import mx.events.ItemClickEvent;
private function Switch(event:ItemClickEvent):void {var keycode:int=event.index;
switch(keycode){//上下左右case 0:grid.dataProvider=a1;break;case 1:
grid.dataProvider=a2;break;case 2:grid.dataProvider=a3;break;case 3:
grid.dataProvider=a4;break;case 4:grid.dataProvider=a5;break;case 5:
grid.dataProvider=dpFlat;break;}}]]--></mx:Script><mx:Panel
layout="absolute"title="数据合并"horizontalCenter="0"
verticalCenter="0" height="220" width="500">
<mx:DataGrid id="grid" dataProvider="{a1}" right="0" bottom="0" top="0" left="0"/>
<mx:ControlBar horizontalAlign="right" ><mx:Spacer width="10%"/>
<mx:ToggleButtonBaritemClick="Switch(event);"bottom="2" id="ToggleButtonBar"
horizontalCenter="0"><mx:dataProvider><mx:Array>
<mx:String>第一</mx:String><mx:String&