Flex中列的数据

<local:CheckBoxDataGrid id="dg" 
                    allowMultipleSelection="true"   x="118" y="151" width="557">
        <local:columns>
            <mx:DataGridColumn dataField="firstName" headerText="Select" width="50" sortable="false" itemRenderer="CheckBoxRenderer" > 
            </mx:DataGridColumn>
            <mx:DataGridColumn id="userID" headerText="User ID" />
            <mx:DataGridColumn dataField="userlevel" editable="true" headerText="Role" />
            <mx:DataGridColumn id="email" headerText="Email" />
        </local:columns>
    </local:CheckBoxDataGrid>

private function getUs(data:Object):void{
         var appSes:ArrayCollection = new ArrayCollection(data.result);
            dg.dataProvider = appSes;
            }
<local:CheckBoxDataGrid id="dg"