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dataGrid控件的showHeaders和headerHeight属性。
示例：

代码：

<? xml version="1.0" encoding="utf-8" ?>
<!--  http://blog.flexexamples.com/2008/06/16/setting-the-header-height-on-a-datagrid-control-in-flex/  -->
< mx:Application  xmlns:mx ="http://www.adobe.com/2006/mxml"
        layout ="vertical"
        verticalAlign ="middle"
        backgroundColor ="white" >

     < mx:Script >
         <![CDATA[
            private function init():void {
                slider.value = dataGrid.headerHeight;
            }
         ]]>
     </ mx:Script >

     < mx:Array  id ="arr" >
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
     </ mx:Array >

     < mx:ApplicationControlBar  dock ="true" >
         < mx:Form  styleName ="plain" >
             < mx:FormItem  label ="headerHeight:" >
                 < mx:HSlider  id ="slider"
                        minimum ="0"
                        maximum ="40"
                        snapInterval ="1"
                        liveDragging ="true"   />
             </ mx:FormItem >
             < mx:FormItem  label ="showHeaders:" >
                 < mx:CheckBox  id ="checkBox"
                        selected ="true"   />
             </ mx:FormItem >
         </ mx:Form >
     </ mx:ApplicationControlBar >

     < mx:DataGrid  id ="dataGrid"
            dataProvider =" {arr} "
            headerHeight =" {slider.value} "
            showHeaders =" {checkBox.selected} "
            initialize ="init();" >
         < mx:columns >
             < mx:DataGridColumn  dataField ="col1"   />
             < mx:DataGridColumn  dataField ="col2"   />
         </ mx:columns >
     </ mx:DataGrid >

</ mx:Application >

也可以通过AS实现：

<? xml version="1.0" encoding="utf-8" ?>
<!--  http://blog.flexexamples.com/2008/06/16/setting-the-header-height-on-a-datagrid-control-in-flex/  -->
< mx:Application  xmlns:mx ="http://www.adobe.com/2006/mxml"
        layout ="vertical"
        verticalAlign ="middle"
        backgroundColor ="white" >

     < mx:Script >
         <![CDATA[
            import mx.events.SliderEvent;

            private function init():void {
                slider.value = dataGrid.headerHeight;
            }

            private function slider_change(evt:SliderEvent):void {
                dataGrid.headerHeight = evt.value;
            }
         ]]>
     </ mx:Script >

     < mx:Array  id ="arr" >
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
         < mx:Object  col1 ="1.One"  col2 ="1.Two"   />
     </ mx:Array >

     < mx:ApplicationControlBar  dock ="true" >
         < mx:Form  styleName ="plain" >
             < mx:FormItem  label ="headerHeight:" >
                 < mx:HSlider  id ="slider"
                        minimum ="0"
                        maximum ="40"
                        snapInterval ="1"
                        liveDragging ="true"
                        change ="slider_change(event);"   />
             </ mx:FormItem >
             < mx:FormItem  label ="showHeaders:" >
                 < mx:CheckBox  id ="checkBox"
                        selected ="true"   />
             </ mx:FormItem >
         </ mx:Form >
     </ mx:ApplicationControlBar >

     < mx:DataGrid  id ="dataGrid"
            dataProvider =" {arr} "
            showHeaders =" {checkBox.selected} "
            initialize ="init();" >
         < mx:columns >
             < mx:DataGridColumn  dataField ="col1"   />
             < mx:DataGridColumn  dataField ="col2"   />
         </ mx:columns >
     </ mx:DataGrid >

</ mx:Application >