android开发教程之使用线程实现视图平滑滚动示例

/**
     * @desc    平滑滚动
     * @param    v        需要操控的视图
     * @param    fromY    起始Y坐标
     * @param    toY        终止Y坐标
     * @param    fps        帧率
     * @param    durtion    动画完成时间（毫秒）   
     * */
    private void smoothScroll(View v, int fromY, int toY, int fps, long durtion) { 
        smoothScrollThread = new SmoothScrollThread(v, fromY, toY, durtion, fps);
        smoothScrollThread.run();
    }

    /**
     * @desc    平滑滚动线程，用于递归调用自己来实现某个视图的平滑滚动
     * */
    class SmoothScrollThread implements Runnable {   
        //需要操控的视图
        private View v = null;     
        //原Y坐标
        private int fromY = 0; 
        //目标Y坐标
        private int toY = 0;     
        //动画执行时间（毫秒）
        private long durtion = 0;     
        //帧率
        private int fps = 60;      
        //间隔时间（毫秒），间隔时间 = 1000 / 帧率
        private int interval = 0;  
        //启动时间，-1 表示尚未启动
        private long startTime = -1;
        /减速插值器
        private DecelerateInterpolator decelerateInterpolator = null;

        /**
         * @desc    构造方法，做好第一次配置
         * */
        public SmoothScrollThread(View v, int fromY, int toY, long durtion, int fps) {
            this.v = v;
            this.fromY = fromY;
            this.toY = toY;
            this.durtion = durtion;
            this.fps = fps;
            this.interval = 1000 / this.fps;      
            decelerateInterpolator = new DecelerateInterpolator();
        }
        @Override
        public void run() {
            //先判断是否是第一次启动，是第一次启动就记录下启动的时间戳，该值仅此一次赋值
            if (startTime == -1) {
                startTime = System.currentTimeMillis();
            }         
            //得到当前这个瞬间的时间戳
            long currentTime = System.currentTimeMillis();     
            //放大倍数，为了扩大除法计算的浮点精度
            int enlargement = 1000;         
            //算出当前这个瞬间运行到整个动画时间的百分之多少
            float rate = (currentTime - startTime) * enlargement / durtion;          
            //这个比率不可能在 0 - 1 之间，放大了之后即是 0 - 1000 之间
            rate = Math.min(rate, 1000);          
            //将动画的进度通过插值器得出响应的比率，乘以起始与目标坐标得出当前这个瞬间，视图应该滚动的距离。
            int changeDistance = (int) ((fromY - toY) * decelerateInterpolator.getInterpolation(rate / enlargement));           
            int currentY = fromY - changeDistance;          
            v.scrollTo(0, currentY);           
            if (currentY != toY) {
                postDelayed(this, this.interval);
            } else {
                return;
            }
        }  
        public void stop() {
            removeCallbacks(this);
        }
    }