一.前言

• 对于更多功能页面，使用RecycleView与TabLayout联动方式实现是比较常见的，先上效果图（请大佬们忽略gif的水印）

• 单独使用TabLayout和RecycleView都是比较容易的，这里就不做举例了；gif中的列表实际上是RecycleView嵌套了RecycleView，嵌套的RecycleView设置了间距（不是本文的重点，代码会在下方贴出来），实现item均分；
• 列表的实现借助了开源库：com.github.CymChad:BaseRecyclerViewAdapterHelper:3.0.4；
• 这里个人先讲解实现思路（会配上局部代码，不要在意代码实现），最后再贴出全部的代码；

二.联动效果的实现

• 联动效果的实现核心在于两个监听的设置。
• 其一：RecycleView需要设置setOnScrollChangeListener，实现滑动RecyclerView列表的时候，根据最上面一个Item的position来切换TabLayout的tab；

mBinding.recyclerView.setOnScrollChangeListener { _, _, _, _, _ ->mBinding.tabLayout.setScrollPosition(mManager!!.findFirstVisibleItemPosition(),0F,true)}

• 其二：TabLayout需要设置addOnTabSelectedListener，点击tab的时候，RecyclerView自动滑到该tab对应的item位置；

mBinding.tabLayout.addOnTabSelectedListener(object : TabLayout.OnTabSelectedListener {override fun onTabSelected(tab: TabLayout.Tab) {
mManager!!.scrollToPositionWithOffset(tab.position, 0)}override fun onTabUnselected(tab: TabLayout.Tab) {}override fun onTabReselected(tab: TabLayout.Tab) {mManager!!.scrollToPositionWithOffset(tab.position, 0)}})

三.细节补充

• 当滑动到RecycleView最后一个item的时候，需要让最后一个item能滑动到
  TabLayout的下方位置，这里的处理方式是：
  • 将RecycleView定义两种不同类型的布局

override fun getItemViewType(position: Int): Int {return if (position == mAllFuncationInfos.size) {2} else {mViewTypeItem}}

• 同时RecycleView的item数量额外+1

 override fun getItemCount(): Int {return mAllFuncationInfos.size + 1}

• 在onCreateViewHolder方法中针对两种不同的item分别返回不同的布局

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BaseViewHolder {return if (viewType == mViewTypeItem) {val view = LayoutInflater.from(parent.context).inflate(mLayoutResId, parent, false)view.post {parentHeight = mRecyclerView.heightitemHeight = view.heightif (itemTitleHeight == 0) {val childNumber = (view as ViewGroup).childCountif (childNumber > 0) {itemTitleHeight = view.getChildAt(0).height}}}ItemViewHolder(view)} else {//Footer是最后留白的位置，以便最后一个item能够出发tab的切换//需要考虑一个问题，若二级列表中有数据和没有数据 Footer的高度计算存在区别val view = View(parent.context)if (lastItemChildrenEmpty) {view.layoutParams =ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,parentHeight - itemTitleHeight)} else {view.layoutParams =ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,parentHeight - itemHeight)}ItemViewHolder(view)}}

• 到此，基本上关键的点都已经完成了，但是呢，还是会有细节。其一：对于TabLayout的addOnTabSelectedListener，如果TabLayout的tab是选中状态，当再次点击的时候，不会执行onTabSelected回调。老规矩，还是上图：
  

• 最开始TabLayout选中的tab是索引为0的tab，当列表滑动了，再次点击索引为0的tab，没有出现联动效果，因为这次执行的回调不是onTabSelected，而是onTabReselected，所以对应的处理方案应该很清楚了；

• 接着讲解其它细节，其二：列表的数据源问题，当传递给嵌套的RecycleView的列表数据为空时，且是最后一个item为空，那么底部留白的高度需要重新计算，在前面onCreateViewHolder方法代码已经贴出相关的代码了。

四.代码环节

• 相关的全部代码

//界面
@Route(path = RouterPathFragment.HomeFour.PAGER_HOME_FOUR)
class ModuleFragment04 :BaseSimpleFragment<ModuleFragment04FragmentHome04Binding>(ModuleFragment04FragmentHome04Binding::inflate) {private val mSpace = DensityU.dip2px(6F)private var mAllFuncationRvAdapter: AllFuncationRvAdapter? = nullprivate var mManager: LinearLayoutManager? = nullprivate var mAllFuncationInfos: MutableList<AllFunctionInfoRes>? = nulloverride fun titBarView(view: View): View = mBinding.funcationTitleBaroverride fun perpareWork() {super.perpareWork()mBinding.funcationTitleBar.leftView.isVisible = false}override fun prepareListener() {super.prepareListener()//滑动RecyclerView list的时候，根据最上面一个Item的position来切换tab
//        mBinding.recyclerView.setOnScrollChangeListener { v, scrollX, scrollY, oldScrollX, oldScrollY ->mBinding.recyclerView.setOnScrollChangeListener { _, _, _, _, _ ->mBinding.tabLayout.setScrollPosition(mManager!!.findFirstVisibleItemPosition(),0F,true)}mBinding.tabLayout.setSelectedTabIndicatorColor(ContextCompat.getColor(requireContext(),R.color.color_000000))mBinding.tabLayout.setTabTextColors(ContextCompat.getColor(requireContext(), R.color.color_ff585858),ContextCompat.getColor(requireContext(), R.color.color_000000))mBinding.tabLayout.addOnTabSelectedListener(object : TabLayout.OnTabSelectedListener {override fun onTabSelected(tab: TabLayout.Tab) {//点击tab的时候，RecyclerView自动滑到该tab对应的item位置//当tab是选中状态，再次点击是不会回调该方法，将下方代码在onTabReselected回调中添加即可解决问题mManager!!.scrollToPositionWithOffset(tab.position, 0)}override fun onTabUnselected(tab: TabLayout.Tab) {}override fun onTabReselected(tab: TabLayout.Tab) {mManager!!.scrollToPositionWithOffset(tab.position, 0)}})mAllFuncationRvAdapter!!.setOpenFunctionActivityInterface(object :AllFuncationRvAdapter.OpenFunctionActivityInterface{override fun openFunctionActivity(childrenBean: AllFunctionInfoRes.ChildrenBean) {openActivityByFunction(childrenBean)}})}private fun openActivityByFunction(childrenBean: AllFunctionInfoRes.ChildrenBean) {val attributesBean: AttributesBean? = childrenBean.attributesif(attributesBean != null){if(attributesBean.appFunctionName == "CardLayout"){openActivityByARouter(RouterPathActivity.SimpleRv.PAGER_SIMPLE_RV);}}}private fun initAdapter() {mAllFuncationInfos = mutableListOf()val jsonListInfos = JsonU.json2List(jsonFileName = "treeListInfo.json",clazz = AllFunctionInfoRes::class.java)if (!jsonListInfos.isNullOrEmpty()) {mAllFuncationInfos!!.addAll(jsonListInfos)}if (!mAllFuncationInfos.isNullOrEmpty()) {val itemChildren =mAllFuncationInfos!![mAllFuncationInfos!!.size - 1].childrenlastItemChildrenEmpty = itemChildren!!.isEmpty()}}var lastItemChildrenEmpty = false@SuppressLint("NotifyDataSetChanged")private fun setAllFuncationData() {mAllFuncationRvAdapter = AllFuncationRvAdapter(mAllFuncationInfos!!, lastItemChildrenEmpty,mBinding.recyclerView, mSpace, R.layout.item_all_funcation)mManager = LinearLayoutManager(context)mBinding.recyclerView.layoutManager = mManagermBinding.recyclerView.adapter = mAllFuncationRvAdapterRecycleViewU.setMaxFlingVelocity(mBinding.recyclerView, 10000)initTablayout()mAllFuncationRvAdapter!!.notifyDataSetChanged()}override fun prepareData() {super.prepareData()initAdapter()setAllFuncationData()}private fun initTablayout() {mBinding.tabLayout.tabMode = TabLayout.MODE_SCROLLABLEfor (i in mAllFuncationInfos!!.indices) {val allFunctionInfoRes = mAllFuncationInfos!![i]mBinding.tabLayout.addTab(mBinding.tabLayout.newTab().setText(allFunctionInfoRes.name).setTag(i))}}}//适配器
class AllFuncationRvAdapter(allFunctionInfoRes: MutableList<AllFunctionInfoRes>,private var lastItemChildrenEmpty: Boolean,recyclerView: RecyclerView,space: Int,layoutResId: Int
) : BaseQuickAdapter<AllFunctionInfoRes, BaseViewHolder>(layoutResId, data = allFunctionInfoRes) {private val mViewTypeItem = 1private var parentHeight = 0private var itemHeight = 0private var itemTitleHeight = 0private var mSpace: Int = spaceprivate var mRecyclerView: RecyclerView = recyclerViewprivate var mAllFuncationInfos: List<AllFunctionInfoRes> = allFunctionInfoResprivate var mLayoutResId = layoutResIdoverride fun convert(holder: BaseViewHolder, item: AllFunctionInfoRes) {//负责将每一个将每一个子项holder绑定数据if (holder.itemViewType == mViewTypeItem) {holder.setText(R.id.item_title_tv, item.name)holder.setImageResource(R.id.item_titie_iv, R.drawable.icon_three)val recyclerView = holder.getView<RecyclerView>(R.id.item_recycler_view)recyclerView.setHasFixedSize(true)recyclerView.layoutManager =GridLayoutManager(ContextU.context(), 4,GridLayoutManager.VERTICAL, false)if (recyclerView.itemDecorationCount == 0) {    //只能设置一次recyclerView.addItemDecoration(GridSpacingItemDecoration(4,mSpace,true))}//            当我们确定Item的改变不会影响RecyclerView的宽高的时候可以设置setHasFixedSize(true)
//            https://blog.csdn.net/wsdaijianjun/article/details/74735039recyclerView.setHasFixedSize(true);//可以做一下缓存 避免每次滑动都重新设置val itemRecyclerViewAdapter =ItemRecyclerViewAdapter(R.layout.item_recycle_inner_content)recyclerView.adapter = itemRecyclerViewAdapteritemRecyclerViewAdapter.setNewInstance(item.children)itemRecyclerViewAdapter.setOnItemClickListener { adapter, _, position ->val childrenBean = adapter.getItem(position) as ChildrenBeanif (mOpenFunctionActivityInterface != null) {mOpenFunctionActivityInterface!!.openFunctionActivity(childrenBean)}}}}override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BaseViewHolder {return if (viewType == mViewTypeItem) {val view = LayoutInflater.from(parent.context).inflate(mLayoutResId, parent, false)view.post {parentHeight = mRecyclerView.heightitemHeight = view.heightif (itemTitleHeight == 0) {val childNumber = (view as ViewGroup).childCountif (childNumber > 0) {itemTitleHeight = view.getChildAt(0).height}}}ItemViewHolder(view)} else {//Footer是最后留白的位置，以便最后一个item能够出发tab的切换//需要考虑一个问题，若二级列表中有数据和没有数据 Footer的高度计算存在区别val view = View(parent.context)if (lastItemChildrenEmpty) {view.layoutParams =ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,parentHeight - itemTitleHeight)} else {view.layoutParams =ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,parentHeight - itemHeight)}ItemViewHolder(view)}}override fun getItemCount(): Int {return mAllFuncationInfos.size + 1}//若使用Java语言开发，则不需要做该处理override fun getItem(position: Int): AllFunctionInfoRes {//需要重写一下该方法做特殊处理if (position == mAllFuncationInfos.size) {       //做拦截处理 避免 super.getItem(position)执行时出现索引越界return AllFunctionInfoRes()                  //返回一个空的AllFunctionInfoRes即可}return super.getItem(position)}override fun getItemViewType(position: Int): Int {return if (position == mAllFuncationInfos.size) {2} else {mViewTypeItem}}internal inner class ItemViewHolder(itemView: View) : BaseViewHolder(itemView)//使用接口回调private var mOpenFunctionActivityInterface: OpenFunctionActivityInterface? = nullinterface OpenFunctionActivityInterface {fun openFunctionActivity(childrenBean: ChildrenBean)}fun setOpenFunctionActivityInterface(openFunctionActivityInterface: OpenFunctionActivityInterface) {mOpenFunctionActivityInterface = openFunctionActivityInterface}
}//适配的布局文件
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="wrap_content"tools:ignore="ResourceName"><LinearLayoutandroid:id="@+id/item_title"android:layout_width="match_parent"android:layout_height="@dimen/dp_30"android:orientation="horizontal"android:gravity="center_vertical"android:layout_marginLeft="@dimen/dp_7"android:layout_marginRight="@dimen/dp_7"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintTop_toTopOf="parent"><ImageViewandroid:id="@+id/item_titie_iv"android:layout_width="@dimen/dp_10"android:layout_height="@dimen/dp_10"android:src="@drawable/icon_three"android:layout_marginLeft="@dimen/dp_8" /><TextViewandroid:id="@+id/item_title_tv"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginLeft="@dimen/dp_4"android:textSize="@dimen/sp_15" /></LinearLayout><androidx.recyclerview.widget.RecyclerViewandroid:id="@+id/item_recycler_view"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_marginTop="@dimen/dp_7"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toBottomOf="@+id/item_title"/></androidx.constraintlayout.widget.ConstraintLayout>//Rv间距设置工具类
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {private int     spanCount;private int     spacing;private boolean includeEdge;public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {this.spanCount = spanCount;this.spacing = spacing;this.includeEdge = includeEdge;}public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, RecyclerView parent, @NonNull RecyclerView.State state) {int position = parent.getChildAdapterPosition(view); // 获取view 在adapter中的位置int column = position % spanCount; // view 所在的列if (includeEdge) {outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)if (position < spanCount) { // 第一行outRect.top = spacing;}outRect.bottom = spacing;} else {//等间距需满足两个条件：//1.各个模块的大小相等，即 各列的left+right 值相等；//2.各列的间距相等，即 前列的right + 后列的left = 列间距；//公式是需要推演的[演示了当列数为2或者3的时候，验证了公式是成立的]： 资料---https://blog.csdn.net/JM_beizi/article/details/105364227//注：这里用的所在列数为从0开始outRect.left = column * spacing / spanCount; //某列的left = 所在的列数 * （列间距 * (1 / 列数)）outRect.right = spacing - (column + 1) * spacing / spanCount; //某列的right = 列间距 - 后列的left = 列间距 -（所在的列数+1） * （列间距 * (1 / 列数)）if (position >= spanCount) {    //说明不是在第一行outRect.top = spacing;}}}
}

五.总结

• TabLayout和RecycleView的联动关键在于两个监听的设置，同时将上方提及的几个细节注意一下即可；