将分页库与 RecyclerView 以外的东西一起使用

Question

我有一个包含大约 5000 个“地点”（即要在地图上显示的纬度和经度）的数据库，我希望能够在地图上显示它们。

现在从 Room 一次性检索 5000 个地点给我带来了麻烦（超过了 this question 中所述的大小限制），所以我想使用分页库检索大约 100 个批次并慢慢填充地图.

然而，Jetpack 附带的 Paging 库似乎非常倾向于将它与 RecyclerView 一起使用，整个 documentation 围绕着构建一个无限滚动的 recyclerview。

所以我想知道是否可以将它与自定义组件一起使用，而不是仅与文档中所述的 PagedAdapter 一起使用。他们提到AsyncPagedListDiffer 有这个签名：

AsyncPagedListDiffer(ListUpdateCallback listUpdateCallback, AsyncDifferConfig<T> config)

所以我继续尝试这样实现：

道：

 @Query("SELECT * FROM places join list_results where places.placeId = list_results.id ORDER by placeName ASC")
    abstract fun getFilteredPlacesPaginated(): DataSource.Factory<Int, PlaceVO>

存储库：

override fun getListPlaces(pageSize: Int, boundaryCallback: PagedList.BoundaryCallback<StateAwarePlace>): Flowable<PagedList<StateAwarePlace>> {
        return placesDao.getFilteredPlacesPaginated().map { StateAwarePlace.state(it) }.toFlowable(pageSize = pageSize, boundaryCallback = boundaryCallback)
    }

视图模型：

val boundaryCallback: PagedList.BoundaryCallback<StateAwarePlace> = object : PagedList.BoundaryCallback<StateAwarePlace>() {
        override fun onZeroItemsLoaded() {
            super.onZeroItemsLoaded()
            Timber.w("PAGINATEDLIST - OnZeroItemsLoaded")
        }

        override fun onItemAtEndLoaded(itemAtEnd: StateAwarePlace) {
            super.onItemAtEndLoaded(itemAtEnd)
            Timber.w("PAGINATEDLIST - onItemAtEndLoaded ${itemAtEnd.place.placeName}")
        }

        override fun onItemAtFrontLoaded(itemAtFront: StateAwarePlace) {
            super.onItemAtFrontLoaded(itemAtFront)
            Timber.w("PAGINATEDLIST - onItemAtFrontLoaded ${itemAtFront.place.placeName}")
        }
    }
    val paginatedPlaces = placesRepository.getListPlaces(50, boundaryCallback).toLiveData()

片段：

val asyncPagedListDiffer = AsyncPagedListDiffer<StateAwarePlace>(object : ListUpdateCallback {
        override fun onChanged(position: Int, count: Int, payload: Any?) {
            Timber.w("PAGINATEDLIST - Item in position $position has changed, now count is $count, payload $payload")
        }

        override fun onMoved(fromPosition: Int, toPosition: Int) {
            Timber.d("PAGINATEDLIST - Item moved from $fromPosition to $toPosition")
        }

        override fun onInserted(position: Int, count: Int) {
            Timber.i("PAGINATEDLIST - Item inserted on position $position, new count is $count")
        }

        override fun onRemoved(position: Int, count: Int) {
            Timber.v("PAGINATEDLIST - Item removed on position $position, count is $count")
        }

    }, PlacesPaginatedAdapter.asyncConfig);


  viewModel.paginatedPlaces.observe(this) { placesList: PagedList<StateAwarePlace> ->


            asyncPagedListDiffer.submitList(placesList)
            asyncPagedListDiffer.addPagedListListener { previousList, currentList ->
                Timber.w("PAGINATEDLIST - Paged list listener ${previousList?.size} to ${currentList?.size}")
            }
        }

但它似乎总是加载总数量的地方。

我也不知道如何告诉 pagedlist 检索更多页面，或者如何使用差异将数据发送到我的地图实例...

toFlowable：

fun <Key, Value> DataSource.Factory<Key, Value>.toFlowable(
    pageSize: Int,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null,
    backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST
): Flowable<PagedList<Value>> {
    return createRxPagedListBuilder(
            dataSourceFactory = this,
            config = Config(pageSize),
            initialLoadKey = initialLoadKey,
            boundaryCallback = boundaryCallback,
            fetchScheduler = fetchScheduler,
            notifyScheduler = notifyScheduler).buildFlowable(backpressureStrategy)
}
private fun <Key, Value> createRxPagedListBuilder(
    dataSourceFactory: DataSource.Factory<Key, Value>,
    config: PagedList.Config,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?
): RxPagedListBuilder<Key, Value> {
    val builder = RxPagedListBuilder(dataSourceFactory, config)
            .setInitialLoadKey(initialLoadKey)
            .setBoundaryCallback(boundaryCallback)
    if (fetchScheduler != null) builder.setFetchScheduler(fetchScheduler)
    if (notifyScheduler != null) builder.setNotifyScheduler(notifyScheduler)
    return builder
}

Answer 1

使用标记聚类处理谷歌地图中大量点的显示 check android-maps-utils sample