Jetpack 分页库无需滚动即可加载所有页面

Question

我使用 PageKeyedDataSource 从网络获取数据。数据共有6页，pagesize为10。

val myPagingConfig = PagedList.Config.Builder()
        .setPageSize(pageSize)
        .setPrefetchDistance(pageSize)
        .setInitialLoadSizeHint(pageSize)
        .setEnablePlaceholders(false)
        .build()

但是分页会触发 5 次 loadAfter，而不需要滚动。然后将加载整个数据

Answer 1

由于在NestedScrollView 中使用了RecyclerView，我遇到了同样的问题。 如果您处于同样的情况，请尝试删除 NestedScrollView 或使用this 而不是 NestedScrollView。 （参考这个answer）

import android.content.Context
import android.util.AttributeSet
import android.view.View
import android.view.ViewGroup
import androidx.core.view.forEach
import androidx.core.widget.NestedScrollView
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

open class SmartNestedScrollView @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : NestedScrollView(context, attrs, defStyleAttr) {

    override fun measureChildWithMargins(child: View, parentWidthMeasureSpec: Int, widthUsed: Int, parentHeightMeasureSpec: Int, heightUsed: Int) {
        if (findNestedRecyclerView(child) != null) {
            val lp = child.layoutParams as MarginLayoutParams
            val childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
                lp.topMargin + lp.bottomMargin, MeasureSpec.AT_MOST
            )
            child.measure(parentWidthMeasureSpec, childHeightMeasureSpec)
        } else {
            super.measureChildWithMargins(child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed)
        }
    }

    private fun findNestedRecyclerView(view: View): RecyclerView? {
        if (view is RecyclerView) {
            val vertical = (view.layoutManager as? LinearLayoutManager)?.orientation == LinearLayoutManager.VERTICAL
            if (vertical) return view
        }

        if (view is ViewGroup) {
            view.forEach { child ->
                val rv = findNestedRecyclerView(child)
                if (rv != null) return rv
            }
        }

        return null
    }
}
 //reference: https://gist.github.com/danaimset/abacaa50d746a4537686a08ecc33c1a9

更新： 如果到达数据末尾（即没有更多数据要加载），请确保将 null 传递给 PagingSource 类中的 nextKey

override suspend fun load(params: LoadParams<String>): LoadResult<String, Wallpost> {

        return try {
            val nextPage = params.key ?: url
            val response = repository.getPostList(nextPage)

            LoadResult.Page(
                data = response.list,
                prevKey = "",
                nextKey = if (response.hasNextPage) response.next else null
            )
        }catch (e: Exception){
            LoadResult.Error(e)
        }
    }