Hello,

I am new to flex development and I am stuck with this error

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at mx.charts.series::LineSeries/findDataPoints()[E:\dev\4.0.0\frameworks\projects\datavisualization\src\mx\charts\series\LineSeries.as:1460]
at mx.charts.chartClasses::ChartBase/findDataPoints()[E:\dev\4.0.0\frameworks\projects\datavisualization\src\mx\charts\chartClasses\ChartBase.as:2202]
at mx.charts.chartClasses::ChartBase/mouseMoveHandler()[E:\dev\4.0.0\frameworks\projects\datavisualization\src\mx\charts\chartClasses\ChartBase.as:4882]

I try to create a chart where I can move the points with the mouse I notice that the error doesn't occur if I move the point very slowly I have try to use the debugger and pint some debug every where without success All the behaviours were ok until I had the modifyData

Please let me know if you have some experience with this kind of error I will appreciate any help. Is it also possible to remove the error throwing because after that the error occur if I click the dismiss all error button then the component work great

there is the simple code of the chart

<fx:Declarations>

</fx:Declarations>

<fx:Script>
    <![CDATA[

        import mx.charts.HitData;
        import mx.charts.events.ChartEvent;
        import mx.charts.events.ChartItemEvent;
        import mx.collections.ArrayCollection;

        [Bindable]
        private var selectItem:Object;

        [Bindable]
        private var chartMouseY:int;

        [Bindable]
        private var hitData:Boolean=false;

        [Bindable]
        private var profitPeriods:ArrayCollection = new ArrayCollection( [
            { period: "Qtr1 2006", profit: 32 },
            { period: "Qtr2 2006", profit: 47 },
            { period: "Qtr3 2006", profit: 62 },
            { period: "Qtr4 2006", profit: 35 },
            { period: "Qtr1 2007", profit: 25 },
            { period: "Qtr2 2007", profit: 55 } ]);



        public function chartMouseUp(e:MouseEvent):void{

            if(hitData){
                hitData = false;    
            }
        }

        private function chartMouseMove(e:MouseEvent):void {

            if(hitData){

                    var p:Point = new Point(linechart.mouseX,linechart.mouseY);
                    var d:Array = linechart.localToData(p);

                    chartMouseY=d[1];                                                           
                    modifyData();

            }   
        }

        public function modifyData():void {

            var idx:int = profitPeriods.getItemIndex(selectItem);   
            var item:Object = profitPeriods.getItemAt(idx);

            item.profit = chartMouseY;                          
            profitPeriods.setItemAt(item,idx);   

        }

        public function chartMouseDown(e:MouseEvent):void{

            if(!hitData){
                var hda:Array = linechart.findDataPoints(e.currentTarget.mouseX, 
                                                         e.currentTarget.mouseY);
                if (hda[0]) {

                    selectItem = hda[0].item;
                    hitData = true;     
                }           
            }
        }
    ]]>
</fx:Script>

<s:layout>

    <s:HorizontalLayout horizontalAlign="center" verticalAlign="middle" />  

</s:layout>


<s:Panel title="LineChart Control" >

    <s:VGroup >

        <s:HGroup>

        <mx:LineChart id="linechart" color="0x323232" height="500" width="377"
                      mouseDown="chartMouseDown(event)"
                      mouseMove="chartMouseMove(event)"
                      mouseUp="chartMouseUp(event)"
                      showDataTips="true" 
                      dataProvider="{profitPeriods}" >

            <mx:horizontalAxis>
                <mx:CategoryAxis categoryField="period"/>
            </mx:horizontalAxis>

            <mx:series>
                <mx:LineSeries yField="profit" form="segment" displayName="Profit"/>
            </mx:series>

        </mx:LineChart>


        <mx:Legend dataProvider="{linechart}" color="0x323232"/>

        </s:HGroup>


        <mx:Form>
            <mx:TextArea id="DEBUG" height="200" width="300"/>
        </mx:Form>


    </s:VGroup>
</s:Panel>

UPDATE 30/2010 : the null object is _renderData.filteredCache from the chartline the code call before error is the default mouseMoveHandler of chartBase to chartline. Is it possible to remove it ? or provide a filteredCache