倒数计时器示例

package {
import flash.events.TimerEvent;
import flash.utils.Timer;

public class CountdownTimer extends Timer {

    public var time:Number = 0;

    public function CountdownTimer(time:Number = Number.NEGATIVE_INFINITY, delay:Number = 1000) {
        super(delay, repeatCount);

        if (!isNaN(time))
            this.time = time;

        repeatCount = Math.ceil(time / delay);

        addEventListener(TimerEvent.TIMER, timerHandler);
        addEventListener(TimerEvent.TIMER_COMPLETE, timerCompleteHandler);
    }

    override public function start():void {
        super.start();
    }

    protected function timerHandler(event:TimerEvent):void {
        time -= delay;
    }

    protected function timerCompleteHandler(event:TimerEvent):void {
    }

    override public function stop():void {
        super.stop();
    }

    public function dispose():void {
        removeEventListener(TimerEvent.TIMER, timerHandler);
        removeEventListener(TimerEvent.TIMER_COMPLETE, timerCompleteHandler);
    }

}
}

这个 CountdownTimer 扩展 Timer，并且使用完全相同，除了时间倒计时。

用法示例：

var timer:CountdownTimer = new CountdownTimer(5000);
timer.addEventListener(TimerEvent.TIMER, timerHandler);
timer.addEventListener(TimerEvent.TIMER_COMPLETE, completeHandler);
timer.start();

function timerHandler(event:TimerEvent):void {
    trace("Time remaining: " + event.target.time);
}

function completeHandler(event:TimerEvent):void {
    trace("Timer complete");
}

以上示例将输出：

[trace] Time remaining: 4000
[trace] Time remaining: 3000
[trace] Time remaining: 2000
[trace] Time remaining: 1000
[trace] Time remaining: 0
[trace] Timer complete