添加Timer

import flash.utils.Timer;
var daojishiTimer:Timer;
//是否添加 时间侦听
function addTimer(_isAdd: Boolean = true) {
	if (_isAdd) {
		daojishiTimer = new Timer(1000);
		daojishiTimer.addEventListener(TimerEvent.TIMER, yunxing); //运行时调用
		daojishiTimer.start(); //启动计时器
	} else {
		if (daojishiTimer) {
			daojishiTimer.removeEventListener(TimerEvent.TIMER, yunxing);
			daojishiTimer.stop();
			daojishiTimer = null;
		}
	}
}

//运行时
function yunxing(evt: TimerEvent): void {
	dangqianshijian--;
	timetxt.text = "" + dangqianshijian + "s";
	if (dangqianshijian == 0) {
		gameOver();
	}
}