问如何在不拉伸文本的情况下更改TextField的宽度？

EN

package src 
{
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.MouseEvent;
    import flash.text.TextField;
    import flash.text.TextFormat;

    public class Main extends Sprite 
    {
        private var tx:TextField;
        private var txf:TextFormat;

        public function Main() 
        {
            addEventListener(Event.ADDED_TO_STAGE, initMain);
        }

        private function initMain(e:Event):void 
        {
            removeEventListener(Event.ADDED_TO_STAGE, initMain);

            // setup a text format so you can keep your text the same all the time.
            txf = new TextFormat('Arial', 12, 0x000000);

            tx = new TextField();
            tx.width = 50;
            tx.text = "I want this text not to wrap so it will be resized at runtime."

            // Turned this on for testing purposes only.
            tx.wordWrap = true;

            tx.defaultTextFormat = txf;     // This line is the x factor most likely.

            tx.x = 100;
            tx.y = 100;

            addChild(tx);

            stage.addEventListener(MouseEvent.CLICK, toggleTextFieldSize, false, 0 ,true);
        }

        private function toggleTextFieldSize(e:MouseEvent):void 
        {
            if (tx.width == 50)
            {
                tx.width = 400;
            }
            else
            {
                tx.width = 50;
            }
        }

    }

}