如何创建一个没有滚动条的动态可缩放的文本框

来自Adobe Devnet：http://www.adobe.com/cfusion/communityengine/index.cfm?event=showdetails&postid=13628&loc=en_US&productid=2问题描述：我需要创建一个固定尺寸的TextArea组件，但是如果用户输入的文本长度超出了TextArea的高度，我希望TextArea能自动改变高度，而不是使用滚动条。解决方案：扩展TextArea，重写text和height属性的Setter方法，并且添加一个事件来侦听文本内容的改变。主要代码：

private function adjustHeightHandler(event:Event):void{
trace("textField.getLineMetrics(0).height: " + textField.getLineMetrics(0).height);
if(height <= textField.textHeight + textField.getLineMetrics(0).height){
height = textField.textHeight;
validateNow();
}
}

演示以及源码下载：http://www.riameeting.com/examples/DynamicTextArea/DynamicTextAreaSample.html点击右键可查看源码

DynamicTextAreaSimple.mxml

<?xml version="1.0" encoding="utf-8" ?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
xmlns:comp="*" creationComplete="init();" viewSourceURL="srcview/index.html">
<mx:Script>
<![CDATA[
import mx.controls.Alert;

private var str:String = "This text will be long enough to trigger " +
"the TextArea to increase its height.";
private function setLargeText():void{
txt1.text = str;
txt2.text = str;
txt3.text = str;
txt4.text = str;
}
]]>
</mx:Script>
<comp:DynamicTextArea id="txt1" width="300" height="14"/>
<comp:DynamicTextArea id="txt2" width="300" height="20"/>
<comp:DynamicTextArea id="txt3" width="300" height="28"/>
<comp:DynamicTextArea id="txt4" width="300" height="50"/>
<mx:Button label="Set Large Text" click="setLargeText();"/>
</mx:Application>

DynamicTextArea.as

package {import flash.events.Event;import mx.controls.TextArea;public class DynamicTextArea extends TextArea{public function DynamicTextArea(){super();super.horizontalScrollPolicy = "off";super.verticalScrollPolicy = "off";this.addEventListener(Event.CHANGE, adjustHeightHandler);}private function adjustHeightHandler(event:Event):void{
trace("textField.getLineMetrics(0).height: " + textField.getLineMetrics(0).height);
if(height <= textField.textHeight + textField.getLineMetrics(0).height){
height = textField.textHeight;
validateNow();
}
}override public function set text(val:String):void{textField.text = val;validateNow();height = textField.textHeight;validateNow();}override public function set height(value:Number):void{if(textField == null){if(height <= value){super.height = value;}}else{var currentHeight:uint = textField.textHeight + textField.getLineMetrics(0).height;if (currentHeight<= super.maxHeight){if(textField.textHeight != textField.getLineMetrics(0).height){super.height = currentHeight;}}else{super.height = super.maxHeight;}}}override public function get text():String{return textField.text;}override public function set maxHeight(value:Number):void{super.maxHeight = value;}}}

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