Android性能优化之RecyclerView分页加载组件功能详解

interface IPagingList<T> {
    fun bindView(context: Context,lifecycleOwner: LifecycleOwner, recyclerView: RecyclerView,adapter: PagingAdapter<T>,mode: ListMode) {}
    fun bindData(model: List<BasePagingModel<T>>) {}
}

open class BasePagingModel<T>(
    var pageCount: String = "", //页码
    var type: Int = 1, //分页类型 1 带日期 2 普通列表
    var time: String = "", //如果是带日期的model，那么需要传入此值
    var itemData: T? = null
)

abstract class PagingAdapter<T> : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
    private var datas: List<BasePagingModel<T>>? = null
    private var maps: MutableMap<String, MutableList<BasePagingModel<T>>>? = null
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        return buildBusinessHolder(parent, viewType)
    }
    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        if (datas != null) {
            bindBusinessData(holder, position, datas)
        } else if (maps != null) {
            bindBusinessMapData(holder, position, maps)
        }
    }
    abstract fun getHolderWidth(context: Context):Int
    override fun getItemCount(): Int {
        return if (datas != null) datas!!.size else 0
    }
    open fun bindBusinessMapData(
        holder: RecyclerView.ViewHolder,
        position: Int,
        maps: MutableMap<String, MutableList<BasePagingModel<T>>>?
    ) {
    }
    open fun bindBusinessData(
        holder: RecyclerView.ViewHolder,
        position: Int,
        datas: List<BasePagingModel<T>>?
    ) {
    }
    abstract fun buildBusinessHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder
    fun setPagingData(datas: List<BasePagingModel<T>>) {
        this.datas = datas
        notifyDataSetChanged()
    }
    fun setPagingMapData(maps: MutableMap<String, MutableList<BasePagingModel<T>>>) {
        this.maps = maps
        notifyDataSetChanged()
    }
}

abstract fun getHolderWidth(context: Context):Int

findFirstVisibleItemPosition()
findLastVisibleItemPosition()
findFirstCompletelyVisibleItemPosition()
findLastCompletelyVisibleItemPosition()

class PagingList<T> : IPagingList<T>, IModelProcess<T>, LifecycleEventObserver {
    private var mTotalScroll = 0
    private var mCallback: IPagingCallback? = null
    private var currentPageIndex = ""
    //模式
    private var mode: ListMode = ListMode.DATE
    private var adapter: PagingAdapter<T>? = null
    //支持的类型 普通列表
    private val dateMap: MutableMap<String, MutableList<BasePagingModel<T>>> by lazy {
        mutableMapOf()
    }
    private val simpleList: MutableList<BasePagingModel<T>> by lazy {
        mutableListOf()
    }
    override fun bindView(
        context: Context,
        lifecycleOwner: LifecycleOwner,
        recyclerView: RecyclerView,
        adapter: PagingAdapter<T>,
        mode: ListMode
    ) {
        this.mode = mode
        this.adapter = adapter
        recyclerView.adapter = adapter
        recyclerView.layoutManager =
            LinearLayoutManager(context, LinearLayoutManager.HORIZONTAL, false)
        addRecyclerListener(recyclerView)
        lifecycleOwner.lifecycle.addObserver(this)
    }
    private fun addRecyclerListener(recyclerView: RecyclerView) {
        recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
                super.onScrollStateChanged(recyclerView, newState)
                if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                    if (!recyclerView.canScrollHorizontally(1) && currentPageIndex == "-1" && mTotalScroll > 0) {
                        //滑动到底部
                        mCallback?.scrollEnd()
                    }
                    //获取可见item的个数
                    val visibleCount = getVisibleItemCount(recyclerView.context, recyclerView)
                    if (recyclerView.childCount > 0 && visibleCount >= (getListCount(mode) ?: 0)) {
                        if (currentPageIndex != "-1") {
                            //请求下一页数据
                            mCallback?.scrollRefresh()
                        }
                    }
                } else {
                    //暂停刷新
                    mCallback?.scrolling()
                }
            }
            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                super.onScrolled(recyclerView, dx, dy)
                if (!recyclerView.canScrollHorizontally(1) && currentPageIndex == "-1" && mTotalScroll > 0) {
                    //滑动到底部
                    mCallback?.scrollEnd()
                }
                mTotalScroll += dx
                //滑动超出2屏
//                binding.ivBackFirst.visibility =
//                    if (mTotalScroll > ScreenUtils.getScreenWidth(requireContext()) * 2) View.VISIBLE else View.GONE
            }
        })
    }
    override fun bindData(model: List<BasePagingModel<T>>) {
        //处理数据
        dealPagingModel(model)
        //adapter刷新数据
        if (mode == ListMode.DATE) {
            adapter?.setPagingMapData(dateMap)
        } else {
            adapter?.setPagingData(simpleList)
        }
    }
    fun setScrollListener(callback: IPagingCallback) {
        this.mCallback = callback
    }
    override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
        if (event == Lifecycle.Event.ON_RESUME) {
            //TODO 加载图片
//            Glide.with(requireContext()).resumeRequests()
        } else if (event == Lifecycle.Event.ON_PAUSE) {
            //TODO 停止加载图片
        } else if (event == Lifecycle.Event.ON_DESTROY) {
            //TODO 页面销毁不会加载图片
        }
    }
    
    private fun getVisibleItemCount(context: Context, recyclerView: RecyclerView): Int {
        var totalCount = 0
        //首屏假设全部占满
        totalCount +=
            ScreenUtils.getScreenWidth(recyclerView.context) / adapter?.getHolderWidth(context)!!
        totalCount += mTotalScroll / adapter?.getHolderWidth(context)!!
        return (totalCount + 1)
    }
    override fun getTotalCount(): Int? {
        return getListCount(mode)
    }
    override fun dealPagingModel(data: List<BasePagingModel<T>>) {
        this.currentPageIndex = updateCurrentPageIndex(data)
        if (mode == ListMode.DATE) {
            data.forEach { model ->
                val time = DateFormatterUtils.check(model.time)
                if (dateMap.containsKey(time)) {
                    model.itemData?.let {
                        dateMap[time]?.add(model)
                    }
                } else {
                    val list = mutableListOf<BasePagingModel<T>>()
                    list.add(model)
                    dateMap[time] = list
                }
            }
        } else {
            simpleList.addAll(data)
        }
    }
    private fun updateCurrentPageIndex(data: List<BasePagingModel<T>>): String {
        if (data.isNotEmpty()) {
            return data[0].pageCount
        }
        return "-1"
    }
    private fun getListCount(mode: ListMode): Int? {
        var count = 0
        if (mode == ListMode.DATE) {
            dateMap.keys.forEach { key ->
                //获取key下的元素个数
                count += dateMap[key]?.size ?: 0
            }
        } else {
            count = simpleList.size
        }
        return count
    }
}

if (!recyclerView.canScrollHorizontally(1) && currentPageIndex == "-1" && mTotalScroll > 0) {
    //滑动到底部
    mCallback?.scrollEnd()
}

private fun getVisibleItemCount(context: Context, recyclerView: RecyclerView): Int {
    var totalCount = 0
    //首屏假设全部占满
    totalCount +=
        ScreenUtils.getScreenWidth(recyclerView.context) / adapter?.getHolderWidth(context)!!
    totalCount += mTotalScroll / adapter?.getHolderWidth(context)!!
    return (totalCount + 1)
}

override fun bindData(model: List<BasePagingModel<T>>) {
    //处理数据
    dealPagingModel(model)
    //adapter刷新数据
    if (mode == ListMode.DATE) {
        adapter?.setPagingMapData(dateMap)
    } else {
        adapter?.setPagingData(simpleList)
    }
}

override fun dealPagingModel(data: List<BasePagingModel<T>>) {
    this.currentPageIndex = updateCurrentPageIndex(data)
    if (mode == ListMode.DATE) {
        data.forEach { model ->
            val time = DateFormatterUtils.check(model.time)
            if (dateMap.containsKey(time)) {
                model.itemData?.let {
                    dateMap[time]?.add(model)
                }
            } else {
                val list = mutableListOf<BasePagingModel<T>>()
                list.add(model)
                dateMap[time] = list
            }
        }
    } else {
        simpleList.addAll(data)
    }
}

if (recyclerView.childCount > 0 && visibleCount >= (getListCount(mode) ?: 0)) {
    if (currentPageIndex != "-1") {
        //请求下一页数据
        mCallback?.scrollRefresh()
    }
}