<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/11/23/hiding-nested-controls-in-a-flex-richtexteditor-control/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:Script>
        <![CDATA[
            import mx.controls.TextInput;

            private function toggle_linkTextInput():void {
                var textInput:TextInput = richTextEditor.linkTextInput;
                var isSelected:Boolean = checkBox.selected;
                textInput.visible = isSelected;
                textInput.includeInLayout = isSelected;
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:CheckBox id="checkBox"
                label="RichTextEditor linkTextInput visible:"
                labelPlacement="left"
                selected="true"
                change="toggle_linkTextInput();" />
    </mx:ApplicationControlBar>

    <mx:RichTextEditor id="richTextEditor" />

</mx:Application>