/// <summary>    
    /// 计算FPS类    
    /// </summary>    
    public static class FpsCounter
    {
        private static int frames;
        private static int milliseconds;
        private static int interval = 1000;
        private static float fps;

        /// <summary> 
        /// 得到当前的FPS 
        /// </summary>        
        public static float Fps
        {
            get { return fps; }
        }

        /// <summary>     
        /// 设置/获取用于计算FPS的时间间隔（毫秒）
        /// 默认值1000     
        /// </summary>        
        public static int Interval
        {
            get { return interval; }
            set { interval = value; }
        }

        /// <summary>     
        /// 在每一帧调用     
        /// </summary>     
        /// <param name="time">自从上一帧经过的时间</param>     
        /// <returns>如果经过的时间大于设置的间隔时间就返回true</returns>        
        public static bool NewFrame(GameTime time)
        {
            frames++;
            milliseconds += time.ElapsedRealTime.Milliseconds;
            if (milliseconds >= interval)
            {
                fps = frames * 1000.0f / (float)milliseconds;
                frames = 0;
                milliseconds -= interval;
                return true;
            }
            return false;
        }
    }