android ScrollView 与SeekBar结合使用

要实现用SeekBar控制ScrollView滚动的位置，并且ScrollView滚动时也更新SeekBar的角度，需要继承ScrollView，实现一个新的类。可以使这个类实现 SeekBar.OnSeekBarChangeListener接口。

覆盖ScrollView的onScrollChanged方法并修改SeekBar.OnSeekBarChangeListener接口中的onProgressChanged方法。关键代码如下 

 int heightMeasure;
        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
            heightMeasure = getMeasuredHeight();
        }
        @Override
        protected void onScrollChanged(int l, int t, int oldl, int oldt) {
            super.onScrollChanged(l, t, oldl, oldt);
            // When the user scrolls, we hide navigation elements.
            if (heightMeasure == 0) {
                Toast.makeText(getContext(), "heightMeansu = 0", Toast.LENGTH_SHORT).show();
            } else {
                //获取ScrollView的第一个子View的高度，也就是ScorllView要展示的内容的高度
                View firstChildView = getChildAt(0);
                int firstChildViewHeight = firstChildView.getHeight();
                if(firstChildViewHeight==0){
                    Toast.makeText(getContext(), "firstChildViewHeight = 0", Toast.LENGTH_SHORT).show();
                }else{
                    //计算出ScrollView所处位置占整体的百分比并设置为SeekBar mSeekView的值
                    int progress = (int) (t * 100.0f / (firstChildViewHeight- heightMeasure));
                    mSeekView.setOnSeekBarChangeListener(null);
                    mSeekView.setProgress(progress);
                    mSeekView.setOnSeekBarChangeListener(this);
                }
//                setNavVisibility(false);
            }
        }

        /**
         * SeakBar值改变时修改ScrollView位置
         * @param seekBar
         * @param progress
         * @param fromUser
         */
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            if (heightMeasure == 0) {
                Toast.makeText(getContext(), "heightMeansu = 0", Toast.LENGTH_SHORT).show();
            } else {
                View firstChildView = getChildAt(0);
                int firstChildViewHeight = firstChildView.getHeight();
                int y = (int) ((firstChildViewHeight - heightMeasure) * progress / 100.0f);
                scrollTo(0, y);
            }
        }