RecyclerView滚动监听处理标题栏渐变，tab吸顶/悬停

一、滚动三种状态展示，如下

1.刚进来标题栏透明

2.上滑标题栏渐变

3.上滑标题栏白色，蓝色Tab吸顶

二、看代码

原理：拿到内容中蓝色tab.getTop的高度

    mRecyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
            super.onScrolled(recyclerView, dx, dy)
            verScroll += dy
            if (verScroll == 0.0f || verScroll < mContentTabTopHeight) {
                val scollYDistance = verScroll / mContentTabTopHeight
                Log.d("onScrolled", "scollYDistance........$scollYDistance")
                tv_head.setTextColor(argbEvaluator.evaluate(scollYDistance, Color.TRANSPARENT, Color.parseColor("#333333")) as Int)
                tv_head.setBackgroundColor(argbEvaluator.evaluate(scollYDistance, Color.TRANSPARENT, Color.WHITE) as Int)
                tv_head_right.setBackgroundColor(Color.TRANSPARENT)
                isChange = true
                if (headTopBar.visibility == View.VISIBLE)
                    headTopBar.visibility = View.GONE
            } else {
                Log.d("onScrolled", "verScroll........$verScroll")
                if (isChange) {
                    isChange = false
                    if (headTopBar.visibility == View.GONE) {
                        headTopBar.visibility = View.VISIBLE
                    }
                    tv_head.run {
                        tv_head.setBackgroundColor(Color.WHITE)
                        tv_head.setTextColor(Color.parseColor("#333333"))
                    }
                    tv_head_right.run {
                        tv_head_right.setBackgroundColor(Color.WHITE)
                    }
                }
                val position: Int? = layoutManager?.findFirstVisibleItemPosition()
                if (currPos != position) {
                    currPos = position
                    tv_head_right.text = "$position"
                }
            }
        }
    })