Flex4 DataGrid ItemRenderer内嵌方式

Flex4 DataGrid ItemRenderer像Flex3一直内嵌ItemRenderer会报空对象引用的错误，如：

<s:GridColumn dataField="title" headerText="Label">

    <s:itemRenderer>

        <fx:Component>

            <s:Image source="assets/img/1.jpg" width="110" height="110"/>

        </fx:Component>

    </s:itemRenderer>

</s:GridColumn>

需要添加GridItemRenderer

<?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"

               xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600"

               creationComplete="application1_creationCompleteHandler()">

    <s:layout>

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

    </s:layout>

    <fx:Script>

        <![CDATA[

            import mx.collections.ArrayCollection;

            import mx.events.FlexEvent;

            [Bindable]

            private var ac:ArrayCollection = new ArrayCollection([

                {img:'1.jpg',name:'黄家驹',record:'再见理想'},

                {img:'2.jpg',name:'BEYOND',record:'海阔天空'}

            ]);

        ]]>

    </fx:Script>

    <s:DataGrid id="gridImage" width="402" height="600" dataProvider="{ac}">

        <s:columns>

            <s:ArrayList>

                <s:GridColumn dataField="img" headerText="ID" width="110">

                    <s:itemRenderer>

                        <fx:Component>

                            <s:GridItemRenderer>

                                <s:Image source="assets/img/{data.img}" width="110" height="110"/>

                            </s:GridItemRenderer>

                        </fx:Component>

                    </s:itemRenderer>

                </s:GridColumn>

                <s:GridColumn dataField="name" headerText="姓名" width="90"></s:GridColumn>

                <s:GridColumn dataField="record" headerText="专辑" width="200"></s:GridColumn>

            </s:ArrayList>

        </s:columns>

    </s:DataGrid>

</s:Application>