androidx.paging.rxjava2

Kotlin |Java

Classes

RxPagingSource	Rx-based compatibility wrapper around PagingSource's suspending APIs.
RxRemoteMediator	RxJava2 compatibility wrapper around RemoteMediator's suspending APIs.

Extension functions summary

For io.reactivex.Flowable
Flowable<PagingData<T>>	Flowable<PagingData<T>>.cachedIn(scope: CoroutineScope) Operator which caches a Flowable of PagingData within a CoroutineScope.

For io.reactivex.Observable
Observable<PagingData<T>>	Observable<PagingData<T>>.cachedIn(scope: CoroutineScope) Operator which caches an Observable of PagingData within a CoroutineScope.

For PagingData
PagingData<T>	PagingData<T>.filterAsync(predicate: (T) -> Single<Boolean>) Returns a PagingData containing only elements matching the given predicate.
PagingData<R>	PagingData<T>.flatMapAsync(transform: (T) -> Single<Iterable<R>>) Returns a PagingData of all elements returned from applying the given transform to each element, as it is loaded.
PagingData<R>	PagingData<T>.insertSeparatorsAsync(generator: (T?, T?) -> Maybe<R>) Returns a PagingData containing each original element, with an optional separator generated by generator, given the elements before and after (or null, in boundary conditions).
PagingData<R>	PagingData<T>.mapAsync(transform: (T) -> Single<R>) Returns a PagingData containing the result of applying the given transform to each element, as it is loaded.

Extension properties summary

For Pager
Flowable<PagingData<Value>>	Pager<Key, Value>.flowable() A Flowable of PagingData, which mirrors the stream provided by Pager.flow, but exposes it as a Flowable.
Observable<PagingData<Value>>	Pager<Key, Value>.observable() An Observable of PagingData, which mirrors the stream provided by Pager.flow, but exposes it as an Observable.

Extension functions

cachedIn

fun <T : Any> Flowable<PagingData<T>>.cachedIn(scope: CoroutineScope): Flowable<PagingData<T>>

Operator which caches a Flowable of PagingData within a CoroutineScope.

cachedIn multicasts pages loaded and transformed by a PagingData, allowing multiple observers on the same instance of PagingData to receive the same events, avoiding redundant work, but comes at the cost of buffering those pages in memory.

Calling cachedIn is required to allow calling submitData on the same instance of PagingData emitted by Pager or any of its transformed derivatives, as reloading data from scratch on the same generation of PagingData is an unsupported operation.

Parameters
scope: CoroutineScope	The CoroutineScope where the page cache will be kept alive. Typically this would be a managed scope such as ViewModel.viewModelScope, which automatically cancels after the PagingData stream is no longer needed. Otherwise, the provided CoroutineScope must be manually cancelled to avoid memory leaks.

cachedIn

fun <T : Any> Observable<PagingData<T>>.cachedIn(scope: CoroutineScope): Observable<PagingData<T>>

Operator which caches an Observable of PagingData within a CoroutineScope.

cachedIn multicasts pages loaded and transformed by a PagingData, allowing multiple observers on the same instance of PagingData to receive the same events, avoiding redundant work, but comes at the cost of buffering those pages in memory.

Calling cachedIn is required to allow calling submitData on the same instance of PagingData emitted by Pager or any of its transformed derivatives, as reloading data from scratch on the same generation of PagingData is an unsupported operation.

Parameters
scope: CoroutineScope	The CoroutineScope where the page cache will be kept alive. Typically this would be a managed scope such as ViewModel.viewModelScope, which automatically cancels after the PagingData stream is no longer needed. Otherwise, the provided CoroutineScope must be manually cancelled to avoid memory leaks.

filterAsync

@JvmName("filter") @CheckResult fun <T : Any> PagingData<T>.filterAsync(predicate: (T) -> Single<Boolean>): PagingData<T>

Returns a PagingData containing only elements matching the given predicate.

flatMapAsync

@JvmName("flatMap") @CheckResult fun <T : Any, R : Any> PagingData<T>.flatMapAsync(transform: (T) -> Single<Iterable<R>>): PagingData<R>

Returns a PagingData of all elements returned from applying the given transform to each element, as it is loaded.

insertSeparatorsAsync

@JvmName("insertSeparators") @CheckResult fun <T : R, R : Any> PagingData<T>.insertSeparatorsAsync(generator: (T?, T?) -> Maybe<R>): PagingData<R>

Returns a PagingData containing each original element, with an optional separator generated by generator, given the elements before and after (or null, in boundary conditions).

Note that this transform is applied asynchronously, as pages are loaded. Potential separators between pages are only computed once both pages are loaded.

import androidx.paging.insertSeparatorsAsync
import androidx.paging.rxjava2.insertSeparatorsAsync

/*
 * Create letter separators in an alphabetically sorted list.
 *
 * For example, if the input is:
 *     "apple", "apricot", "banana", "carrot"
 *
 * The operator would output:
 *     "A", "apple", "apricot", "B", "banana", "C", "carrot"
 */
pagingDataStream.map { pagingData ->
    // map outer stream, so we can perform transformations on each paging generation
    pagingData.insertSeparatorsAsync { before: String?, after: String? ->
        Maybe.fromCallable<String> {
            if (after != null && before?.first() != after.first()) {
                // separator - after is first item that starts with its first letter
                after.first().toUpperCase().toString()
            } else {
                // no separator - either end of list, or first letters of before/after are the same
                null
            }
        }.subscribeOn(Schedulers.computation())
    }
}

import androidx.paging.insertSeparatorsAsync
import androidx.paging.map
import androidx.paging.rxjava2.insertSeparatorsAsync

open class UiModel
data class ItemUiModel(val item: Item) : UiModel()
data class SeparatorUiModel(val char: Char) : UiModel()

/*
 * Create letter separators in an alphabetically sorted list of Items, with UiModel objects.
 *
 * For example, if the input is (each an `Item`):
 *     "apple", "apricot", "banana", "carrot"
 *
 * The operator would output a list of UiModels corresponding to:
 *     "A", "apple", "apricot", "B", "banana", "C", "carrot"
 */
pagingDataStream.map { pagingData ->
    // map outer stream, so we can perform transformations on each paging generation
    pagingData
        .map { item ->
            ItemUiModel(item) // convert items in stream to ItemUiModel
        }
        .insertSeparatorsAsync { before: ItemUiModel?, after: ItemUiModel? ->
            Maybe.fromCallable<UiModel> {
                if (after != null && before?.item?.label?.first() != after.item.label.first()) {
                    // separator - after is first item that starts with its first letter
                    SeparatorUiModel(after.item.label.first().toUpperCase())
                } else {
                    // no separator - either end of list, or first letters of before/after are the same
                    null
                }
            }.subscribeOn(Schedulers.computation())
        }
}

mapAsync

@JvmName("map") @CheckResult fun <T : Any, R : Any> PagingData<T>.mapAsync(transform: (T) -> Single<R>): PagingData<R>

Returns a PagingData containing the result of applying the given transform to each element, as it is loaded.

Extension properties

flowable

val <Key : Any, Value : Any> Pager<Key, Value>.flowable: Flowable<PagingData<Value>>

A Flowable of PagingData, which mirrors the stream provided by Pager.flow, but exposes it as a Flowable.

observable

val <Key : Any, Value : Any</