flex 基础 为什么柱状图界面与数据无法锁定？

<!--柱状图-->

mx:horizontalAxis

/mx:horizontalAxis
mx:series


/mx:series
/mx:ColumnChart
/s:Panel

fx:Script
<![CDATA[
import mx.collections.ArrayCollection;

        import mx.controls.Alert;

        //记录每月收入支出的数据集
        [Bindable]
        public var  finance:ArrayCollection=new ArrayCollection([
            {month:"一月",In:2000,out:1500},
            {month:"二月",In:1000,out:200},
            {month:"三月",In:1500,out:200},
            {month:"四月",In:3500,out:1000},
            {month:"五月",In:500,out:800},
            {month:"六月",In:4500,out:600},
            {month:"七月",In:2500,out:500},
            {month:"八月",In:1570,out:300},
            {month:"九月",In:1000,out:450},
            {month:"十月",In:1500,out:400},
            {month:"十一月",In:1700,out:2500},
            {month:"十二月",In:1800,out:1500},

        ])


    ]]>
</fx:Script>

这一行中的categoryField要跟finance中的字段名称对应，应该为month