[转] 倒计时抢答

package 
{
        import flash.display.Sprite;
        import flash.events.Event;
        import flash.events.KeyboardEvent;
        import flash.events.MouseEvent;
        import flash.events.TimerEvent;
        import flash.utils.Timer;
        
        /**
         * @author FLASH023
         * @date 2011-5-4 24:14
        **/
        public class JBKey extends Sprite  
        {
                private var timer:Timer;
                private var time:uint;
                public function JBKey():void {
                        timer = new Timer(1000);
                        timer.addEventListener (TimerEvent.TIMER , onTimer);
                        reset_btn.addEventListener (MouseEvent.CLICK, onClick);
                        onClick(null);
                }
                
                private function onClick(e:MouseEvent):void 
                {
                        time = 10;
                        timer.reset();
                        timer.start ();                
                        reset_btn.enabled = false;
                        key_txt.text = "";
                }
                
                private function onTimer(e:TimerEvent ):void 
                {
                        time_txt.text = --time+"";
                        if (time <= 0) {
                                timer.stop();
                                reset_btn.enabled = true;
                                stage.addEventListener (KeyboardEvent.KEY_DOWN, kewDown);
                        }
                }
                
                private function kewDown(e:KeyboardEvent):void 
                {
                        key_txt.text = String.fromCharCode(e.keyCode)+"";
                        //                        
                        stage.removeEventListener (KeyboardEvent.KEY_DOWN, kewDown);
                }
        }
        
}