如何使不同的视图 RecyclerView 成为无限循环？答案

【问题标题】：How to make different views RecyclerView as endless loop?如何使不同的视图 RecyclerView 成为无限循环？
【发布时间】：2018-11-05 11:51:45
【问题描述】：

我一直在寻找制作recyclerview Carousel，以便在最后一个项目可见时再次填充第一个项目，并且它会一次又一次地显示。现在我知道这个答案已经回答了here 和here，但是这两个答案都没有解决我的问题。尽管项目数量增加了，但作为 recyclerview 中的项目的片段没有显示任何内容。

我将fragments 膨胀为嵌套在ViewPager 中的RecyclerView 的一个项目。接受的答案无法解决我的问题。

代码： RecyclerViewAdapterClass

fun initialize(scrollableData: ArrayList<ScrollableData>, activity: AppCompatActivity) {
        this.scrollableData = scrollableData
        this.activity = activity
    }

    override fun getItemCount() = scrollableData.size

    override fun getItemViewType(position: Int): Int {
        return scrollableData[position].index
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BaseHolder {

        when (viewType) {
            ScrollableItems.ABC -> {
                val view = parent.inflate(R.layout.view_module_abc, false)
                return ABCViewHolder(view, abcPresenterImpl, activity)
            }

            ScrollableItems.DEF -> {
                val view = parent.inflate(R.layout.view_module_def, false)
                return DEFViewHolder(view, defControlPresenter, activity)
            }

            else -> {
                val view = parent.inflate(R.layout.view_module_ghi, false)
                return GHIViewHolder(view, GHIModulePresenter, activity)
            }
        }
    }

    override fun onBindViewHolder(holder: BaseHolder, position: Int) {
        holder.bindView()
    }

和HomeActivity#setupRecyclerView(...)

private fun setupRecyclerView(scrollableDataList: ArrayList<ScrollableData>) {
        linearLayoutManager = CustomLinearLayoutManager(applicationContext, LinearLayout.HORIZONTAL, !DeviceConfig.instance!!.isRegularDevice)
        recycler_view.layoutManager = linearLayoutManager
        recycler_view.adapter = mainScreenAdapter

        mainScreenAdapter.initialize(scrollableDataList, this)
        recycler_view.setHasFixedSize(true);
        GravityPagerSnapHelper(if (DeviceConfig.instance!!.isRegularDevice) Gravity.START else Gravity.END, true, this).attachToRecyclerView(recycler_view)
        recyclerViewScrollListener()
    }

和 CustomLinearLayoutManager

class CustomLinearLayoutManager(context: Context, orientation: Int, reverseLayout: Boolean)
    : LinearLayoutManager(context, orientation, reverseLayout) {

    var isScrollEnabled = true

    override fun canScrollHorizontally(): Boolean {
        return isScrollEnabled && super.canScrollHorizontally()
    }

    override fun canScrollVertically(): Boolean {
        return isScrollEnabled && super.canScrollVertically()
    }
}

请帮我解决这个问题。

【问题讨论】：

你可以尝试使用this库。
@AshuTyagi 它没有帮助。

标签： android kotlin android-recyclerview

【解决方案1】：

所以经过大量搜索，找到了this 解决方案。

这就是我所做的

RecyclerViewAdapterClass

  fun initialize(scrollableData: ArrayList<ScrollableData>, activity: AppCompatActivity) {
            this.scrollableData = scrollableData
            this.activity = activity
            list = /*listOf(scrollableData.last()) +*/ scrollableData + listOf(scrollableData.first()) //this is very important
            }
    ...
      override fun getItemViewType(position: Int): Int {
        return list[position %  list.size].index
    }

HomeActivity#setupRecyclerView(...)

mainScreenAdapter.itemCount.takeIf { it > 1 }
                ?.apply {
                    onScrollListener = OnScrollListener(
                            mainScreenAdapter.itemCount,
                            linearLayoutManager
                    ) {
                       //some code here
                    }
                    recycler_view.addOnScrollListener(onScrollListener)
                    recycler_view.scrollToPosition(0)
                }

OnScrollListener

internal class OnScrollListener(val itemCount: Int, val layoutManager: LinearLayoutManager,
                                    val stateChanged: (Int) -> Unit) : RecyclerView.OnScrollListener() {
        var isLooping = false
        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
            super.onScrolled(recyclerView!!, dx, dy)
            val firstItemVisible = layoutManager.findFirstCompletelyVisibleItemPosition()

            if (firstItemVisible > 0 && firstItemVisible % (itemCount - 1) == 0) {
                // When position reaches end of the list, it sho    uld go back to the beginning
                isLooping = true
                recyclerView?.scrollToPosition(0)
            } /*else if (firstItemVisible == 0) {
                // When position reaches beginning of the list, it should go back to the end
                recyclerView?.scrollToPosition(itemCount-1)
            }*/
        }

        override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
            super.onScrollStateChanged(recyclerView!!, newState)
            var loop = newState
            if (isLooping) {
                loop = 100
                isLooping = false
            }
            stateChanged(loop)
        }
    }

参考：https://github.com/tomoima525/CirculerAutoScrollingRecyclerView

【讨论】：