I need some help with my code.

I got this error: Data binding will not be able to detect assignment to "chartData".

Marked with "HERE"

Code:

<?xml version="1.0" encoding="utf-8"?>

<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"

                        xmlns:s="library://ns.adobe.com/flex/spark" applicationDPI="160"

                        xmlns:mx="library://ns.adobe.com/flex/mx"

                        applicationComplete="applicationCompleteHandler(event)">

       <fx:Script>

              <![CDATA[

                     import be.aboutme.nativeExtensions.udp.UDPSocket;                   

                     import mx.events.FlexEvent;             

                     private var udpSocket:UDPSocket;

                     public var NewValue:Object;      

                     public var Value:String;

                     [Bindable]                

                     private var chartIndex:int = 0;

                     private var chartData:ArrayCollection = new ArrayCollection;

                     import mx.collections.ArrayCollection;

                     protected function applicationCompleteHandler(event:FlexEvent):void

                     {

                           udpSocket = new UDPSocket();

                           udpSocket.addEventListener(DatagramSocketDataEvent.DATA, udpDataHandler);

                           udpSocket.bind(1000);

                           udpSocket.receive();

                     }

                     protected function udpDataHandler(event:DatagramSocketDataEvent):void

                     {

                           var Value:String = event.data.readUTFBytes(event.data.bytesAvailable);

                           if(Value)

                           {

                                  NewValue = Value;

                                  Test.appendText(Value);

                                  chartData.source[chartIndex] = NewValue;

                           }

                           else

                           {

                                  NewValue = 0;

                           }

                     }

              ]]>

       </fx:Script>

       <fx:Declarations>

              <!-- Place non-visual elements (e.g., services, value objects) here -->

              <mx:SolidColorStroke id="s3" color="0x33F400" weight="1"/>

       </fx:Declarations>

       <s:layout>          

              <s:VerticalLayout paddingBottom="10" paddingLeft="10" paddingRight="10" paddingTop="10" />

       </s:layout>

       <s:Scroller width="100%" height="100%">

              <s:VGroup width="100%">

                     <s:TextArea id="Test" width="100%" height="49" editable="false"/>

                     <s:HGroup width="100%">

                     </s:HGroup>

              </s:VGroup>

       </s:Scroller>

       <mx:CartesianChart id="linechart" width="100%" height="207" cacheAsBitmap="true"

                                     cachePolicy="on" paddingLeft="5" paddingRight="5">

              <mx:verticalAxis>

                     <mx:LinearAxis id="vAxis" alignLabelsToInterval="true" autoAdjust="false"

                                            baseAtZero="false" interval="16" maximum="256" minimum="0" padding="1"/>

              </mx:verticalAxis>

              <mx:verticalAxisRenderers>

                     <mx:AxisRenderer axis="{vAxis}" canDropLabels="true" color="0xF8F8F6" fontSize="8"/>

              </mx:verticalAxisRenderers>

              <mx:horizontalAxis>

                     <mx:LinearAxis id="hAxis" alignLabelsToInterval="true" autoAdjust="false"

                                            baseAtZero="false" interval="25"/>

              </mx:horizontalAxis>

              <mx:horizontalAxisRenderers>

                     <mx:AxisRenderer axis="{hAxis}" canDropLabels="true" color="0xF8F8F6" fontSize="8"/>

              </mx:horizontalAxisRenderers>

              <mx:fill>

                     <mx:SolidColor color="0x231F20"/>

              </mx:fill>

              <mx:backgroundElements>

                     <mx:GridLines cacheAsBitmap="true" cachePolicy="on" gridDirection="horizontal">

                           <mx:horizontalStroke>

                                  <s:SolidColorStroke alpha="0.2" color="0xD4D4D3" weight="0"/>

                           </mx:horizontalStroke>

                     </mx:GridLines>

              </mx:backgroundElements>

              <mx:series>

  HERE --------->                   <mx:LineSeries id="recordGraph" cacheAsBitmap="true" cachePolicy="on"

                                            dataProvider="{chartData}" form="curve" lineStroke="{s3}"

                                            sortOnXField="false"/>

              </mx:series>

       </mx:CartesianChart>

</s:Application>