RecyclerView 根据滑动位置动态改变背景透明度

RecyclerView 根据滑动位置动态改变背景透明度

根据滑动位置动态改变背景透明度,直接上代码：

binding.recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
    override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
        super.onScrolled(recyclerView, dx, dy)
        onRecyclerScrolled(recyclerView, dx, dy)
    }

    override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
        super.onScrollStateChanged(recyclerView, newState)
    }
})

private val dp180 = dp2px(180)
private var distanceY = 0
private var current = 0
private fun onRecyclerScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
    distanceY += dy
    when {
        distanceY >= dp180 -> {
            if (current == 1) return
            recyclerView.setBackgroundColor(Color.argb(255, 246, 248, 250))
            current = 1
        }
        distanceY <= 0 -> {
            if (current == 0) return
            recyclerView.setBackgroundColor(Color.argb(0, 246, 248, 250))
            current = 0
        }
        else -> {
            recyclerView.setBackgroundColor(
                Color.argb(
                    distanceY * 255 / dp180,
                    246, 248, 250
                )
            )
            current = -1
        }
    }
}