屏幕震动效果

package tools {
    import flash.display.DisplayObject;
    import flash.events.TimerEvent;
    import flash.utils.Timer;    

    public class Earthquake {
       /**
        * 参数
        */
        private var _timer:Timer;
        private var _displayObject:DisplayObject;
        private var _originalX:int;
        private var _originalY:int;
        private var _intensity:int;
        private var _intensityOffset:int;
		/**
		 * 时间
		 */
		private var _seconds:Number;
		/**
		 * 方向
		 */
		public static const LEFT_RIGHT_UP_DOWN:int = 0;
		public static const LEFT_RIGHT:int = 1;
		public static const UP_DOWN:int = 2;
		/**
		 * 帧频
		 */
		public static const FRAME_RATE:int = 60;
		/**
		 * 方向
		 */
		private var _direction:int;
		/**
		 * 震动中
		 */
		private var _bShaking:Boolean = false;
		/**
		 * 是否自动销毁
		 */
		private var _bDestroy:Boolean = false;
		
		 /**
		  * 对一个显示对象应用地震效果。
		  * @param	displayObject 抖动对象
		  * @param	intensity 强度
		  * @param	seconds 持续时间 秒
		  * @param	direction 方向
		  * @param	autoDestroy 自动销毁
		  */
		public function Earthquake(displayObject:DisplayObject, intensity:Number = 10, seconds:Number = 1, direction:int = 0, autoDestroy:Boolean = false):void
		{
            _displayObject = displayObject;
            _originalX = displayObject.x;
            _originalY = displayObject.y;
			_intensity = intensity;
            _intensityOffset = intensity / 2;
			_seconds = seconds;
			_direction = direction;
			_bDestroy = autoDestroy;
		}
		/**
		 * 开始后抖动
		 */
		public function go():void
		{
			if (_bShaking) return;
			_bShaking = true;
			var msPerUpdate:int = int(1000 / FRAME_RATE);
            var totalUpdates:int = int(_seconds * 1000 / msPerUpdate);
			
			if (!_timer)
			{
				_timer = new Timer(msPerUpdate, totalUpdates);
				_timer.addEventListener(TimerEvent.TIMER, quake);
				_timer.addEventListener(TimerEvent.TIMER_COMPLETE, resetImage);
			}
			else
			{
				_displayObject.x = _originalX;
				_displayObject.y = _originalY;
				_timer.reset();
			}
            _timer.start();
		}
		/**
		 * 抖动
		 * @param	event
		 */
        private function quake( event:TimerEvent ):void 
		{
			var newX:int = _originalX;
			var newY:int = _originalY;
			
			switch(_direction)
			{
				case LEFT_RIGHT_UP_DOWN:
					newX = _originalX + Math.random() * _intensity - _intensityOffset;
					newY = _originalY + Math.random() * _intensity - _intensityOffset;
					break;
				case LEFT_RIGHT:
					newX = _originalX + Math.random() * _intensity - _intensityOffset;
					break;
				case UP_DOWN:
					newY = _originalY + Math.random() * _intensity - _intensityOffset;
					break;
			}
            _displayObject.x = newX;
            _displayObject.y = newY;
        }
		/**
		 * 重置
		 * @param	event
		 */
        private function resetImage( event:TimerEvent = null ):void
		{
            _displayObject.x = _originalX;
            _displayObject.y = _originalY;
            cleanup();
        }
		/**
		 * 清除
		 */
        private function cleanup():void 
		{
			_bShaking = false;
            /*_timer = null;
			_timer.stop();*/
			_timer.reset();
			if (_bDestroy)
			{
				_timer.removeEventListener(TimerEvent.TIMER, quake);
				_timer.removeEventListener(TimerEvent.TIMER_COMPLETE, resetImage);
				_timer = null;
				_displayObject = null;
			}
			delete [this];
            //_displayObject = null;
        }
    }
}