Android RecyclerView スクロール用に Firestore データを効率的にページネーションする方法?

// ...

// Define the query limit
private val limit = 15

// Initial query
val query = productsRef.orderBy("productName", Query.Direction.ASCENDING).limit(limit)

query.get().addOnCompleteListener { task ->
    if (task.isSuccessful) {
        for (document in task.result!!) {
            val productModel = document.toObject(ProductModel::class.java)
            list.add(productModel)
        }
        productAdapter.notifyDataSetChanged()
        lastVisible = task.result!!.documents[task.result!!.size() - 1]

        // RecyclerView scroll listener
        recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
                super.onScrollStateChanged(recyclerView, newState)
                if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
                    isScrolling = true
                }
            }

            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                super.onScrolled(recyclerView, dx, dy)

                val linearLayoutManager = recyclerView.layoutManager as LinearLayoutManager
                val firstVisibleItemPosition = linearLayoutManager.findFirstVisibleItemPosition()
                val visibleItemCount = linearLayoutManager.childCount
                val totalItemCount = linearLayoutManager.itemCount

                if (isScrolling && (firstVisibleItemPosition + visibleItemCount == totalItemCount) && !isLastItemReached) {
                    isScrolling = false
                    val nextQuery =
                        productsRef.orderBy("productName", Query.Direction.ASCENDING).startAfter(lastVisible).limit(limit)
                    nextQuery.get().addOnCompleteListener { t ->
                        if (t.isSuccessful) {
                            for (d in t.result!!) {
                                val productModel = d.toObject(ProductModel::class.java)
                                list.add(productModel)
                            }
                            productAdapter.notifyDataSetChanged()
                            lastVisible = t.result!!.documents[t.result!!.size() - 1]

                            if (t.result!!.size() < limit) {
                                isLastItemReached = true
                            }
                        }
                    }
                }
            }
        })
    }
}

// ...