Flex中如何通过includeInLayout和visible属性设置Form显示或隐藏

<?xml version="1.0" encoding="utf-8"?>
<mx:Application name="FormItem_includeInLayout_test1"
xmlns:mx="http://www.adobe.com/2006/mxml"
layout="vertical"
verticalAlign="middle"
backgroundColor="white">

<mx:Style>
Form {
indicatorGap: 0;
paddingLeft: 0;
paddingRight: 0;
paddingTop: 0;
paddingBottom: 0;
}
</mx:Style>

<mx:ApplicationControlBar dock="true">
<mx:Button id="textButton"
label="Show Text 1"
toggle="true"
selected="false" />
</mx:ApplicationControlBar>

<mx:HBox width="100%">

<mx:Form width="100%">

<mx:FormItem label="To:" width="100%">
<mx:TextInput id="toTextInput1"
width="100%" />
</mx:FormItem>

<mx:FormItem label="Text 1:"
includeInLayout="{textButton.selected}"
visible="{textButton.selected}"
width="100%">
<mx:TextInput id="TextInput2"
width="100%" />
</mx:FormItem>

</mx:Form>
</mx:HBox>
</mx:Application>