RecyclerView吸顶终极方案Adsorbent

吸顶终极方案github地址: Adsorbent

1. Single RecyclerView：简单模式
【利用RecyclerView.OnScrollListener监听滑动位置，吸顶View被 ViewHolder和Activity复用】

2. Double RecyclerView：RecyclerView嵌套RecyclerView
【事件分发，吸顶View是个单独ViewHolder,无须做其他处理】

3. Viewpager RecyclerView:RecyclerView嵌套ViewPager(其中包含的页面内容是RecyclerView)
【事件分发，吸顶View是个单独ViewHolder,无须做其他处理】

1.onScrolled机制

abstract class SingleAdsorbentListener : RecyclerView.OnScrollListener(){

    /** 获取被吸顶ViewGroup*/
    abstract fun getUiViewGroup():ViewGroup
    /** 获取吸顶View*/
    abstract fun getPinView(): View
    /** 获取吸顶View在RecyclerView中的位置*/
    abstract fun getPinViewPosition():Int
    /** 吸顶的时候 停止滚动并定位在吸顶位置*/
    fun stopWhenAdsorbent():Boolean = true

    fun getPinViewLayoutParam():ViewGroup.LayoutParams =
        ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT)

    override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
        val manager = recyclerView.layoutManager
        if(manager is LinearLayoutManager) {
            val first = manager.findFirstVisibleItemPosition()
            val last = manager.findLastVisibleItemPosition()
            //val down = recyclerView.canScrollVertically(1)
            //val up = recyclerView.canScrollVertically(-1)
            //Log.e("xx", "first=$first, vertically down=$down, up=$up, dy=$dy")
            val position = getPinViewPosition()
            if (first >= position && dy > 0) {
                addPin2Ui(recyclerView,position)
            } else if (position in (first + 1)..last) {
                addPin2ViewHolder(recyclerView,position-first)
            }
        }
    }