PagingData

public static final @NonNull PagingData<@NonNull T> <T extends Object> empty()

Create a PagingData that immediately displays an empty list of items when submitted to a presenter. E.g., androidx.paging.AsyncPagingDataAdapter and dispatches LoadState.NotLoading on all LoadStates to the presenter.

public static final @NonNull PagingData<@NonNull T> <T extends Object> empty(
    @NonNull LoadStates sourceLoadStates,
    LoadStates mediatorLoadStates
)

Create a PagingData that immediately displays an empty list of items when submitted to a presenter. E.g., androidx.paging.AsyncPagingDataAdapter.

public static final @NonNull PagingData<@NonNull T> <T extends Object> from(@NonNull List<@NonNull T> data)

Create a PagingData that immediately displays a static list of items when submitted to a presenter. E.g., androidx.paging.AsyncPagingDataAdapter and dispatches LoadState.NotLoading on all LoadStates to the presenter.

public static final @NonNull PagingData<@NonNull T> <T extends Object> from(
    @NonNull List<@NonNull T> data,
    @NonNull LoadStates sourceLoadStates,
    LoadStates mediatorLoadStates
)

Create a PagingData that immediately displays a static list of items when submitted to a presenter. E.g., androidx.paging.AsyncPagingDataAdapter.

public final @NonNull PagingData<@NonNull T> <T extends Object> PagingDataFutures.filterAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull AsyncFunction<@NonNull T, @NonNull Boolean> predicate,
    @NonNull Executor executor
)

Returns a PagingData containing only elements matching the given predicate.

public final @NonNull PagingData<@NonNull R> <T extends Object, R extends Object> PagingDataFutures.flatMapAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull AsyncFunction<@NonNull T, @NonNull Iterable<@NonNull R>> transform,
    @NonNull Executor executor
)

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

public final @NonNull PagingData<@NonNull R> <T extends R, R extends Object> PagingDataFutures.insertSeparatorsAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull AsyncFunction<@NonNull AdjacentItems<@NonNull T>, R> generator,
    @NonNull Executor executor
)

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.AdjacentItems
import androidx.paging.insertSeparators
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(
        AsyncFunction<AdjacentItems<String>, String?> {
            Futures.submit(
                Callable<String?> {
                    val (before, after) = it!!
                    if (after != null && before?.first() != after.first()) {
                        // separator - after is first item that starts with its first letter
                        after.first().uppercaseChar().toString()
                    } else {
                        // no separator - either end of list, or first letters of before/after are the same
                        null
                    }
                },
                executor
            )
        },
        executor
    )
}

import androidx.paging.AdjacentItems
import androidx.paging.insertSeparators
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(
            AsyncFunction<AdjacentItems<ItemUiModel>, UiModel?> {
                Futures.submit(
                    Callable<UiModel> {
                        val (before, after) = it!!
                        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().uppercaseChar())
                        } else {
                            // no separator - either end of list, or first letters of before/after are the same
                            null
                        }
                    },
                    executor
                )
            },
            executor
        )
}

public final @NonNull PagingData<@NonNull R> <T extends Object, R extends Object> PagingDataFutures.mapAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull AsyncFunction<@NonNull T, @NonNull R> transform,
    @NonNull Executor executor
)

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

public final @NonNull PagingData<@NonNull T> <T extends Object> PagingDataTransforms.filter(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Executor executor,
    @NonNull Function1<@NonNull T, @NonNull Boolean> predicate
)

Returns a PagingData containing only elements matching the given predicate.

public final @NonNull PagingData<@NonNull R> <T extends Object, R extends Object> PagingDataTransforms.flatMap(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Executor executor,
    @NonNull Function1<@NonNull T, @NonNull Iterable<@NonNull R>> transform
)

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

public final @NonNull PagingData<@NonNull T> <T extends Object> PagingDataTransforms.insertFooterItem(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull TerminalSeparatorType terminalSeparatorType,
    @NonNull T item
)

Returns a PagingData containing each original element, with the passed footer item added to the end of the list.

The footer item is added to a loaded page which marks the end of the data stream in the LoadType.APPEND direction, either by returning null in PagingSource.LoadResult.Page.nextKey. It will be removed if the last page in the list is dropped, which can happen in the case of loaded pages exceeding PagingConfig.maxSize.

Note: This operation is not idempotent, calling it multiple times will continually add more footers to the end of the list, which can be useful if multiple footer items are required.

public final @NonNull PagingData<@NonNull T> <T extends Object> PagingDataTransforms.insertHeaderItem(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull TerminalSeparatorType terminalSeparatorType,
    @NonNull T item
)

Returns a PagingData containing each original element, with the passed header item added to the start of the list.

The header item is added to a loaded page which marks the end of the data stream in the LoadType.PREPEND direction by returning null in PagingSource.LoadResult.Page.prevKey. It will be removed if the first page in the list is dropped, which can happen in the case of loaded pages exceeding PagingConfig.maxSize.

Note: This operation is not idempotent, calling it multiple times will continually add more headers to the start of the list, which can be useful if multiple header items are required.

public final @NonNull PagingData<@NonNull R> <R extends Object, T extends R> PagingDataTransforms.insertSeparators(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull TerminalSeparatorType terminalSeparatorType,
    @NonNull Executor executor,
    @NonNull Function2<T, T, R> generator
)

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.

Kotlin callers should instead use the suspending extension function variant of insertSeparators

/*
 * 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
        PagingDataTransforms.insertSeparators(pagingData, bgExecutor,
                (@Nullable String before, @Nullable String after) -> {
                    if (after != null && (before == null
                            || before.charAt(0) != after.charAt(0))) {
                        // separator - after is first item that starts with its first
                        // letter
                        return Character.toString(
                                Character.toUpperCase(after.charAt(0)));
                    } else {
                        // no separator - either end of list, or first
                        // letters of items are the same
                        return null;
                    }
                }));

/*
 * 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(itemPagingData -> {
    // map outer stream, so we can perform transformations on each paging generation

    // first convert items in stream to UiModel.Item
    PagingData<UiModel.ItemModel> itemModelPagingData = PagingDataTransforms.map(
            itemPagingData, bgExecutor, UiModel.ItemModel::new);

    // Now insert UiModel.Separators, which makes the PagingData of generic type UiModel
    return PagingDataTransforms.insertSeparators(
            itemModelPagingData, bgExecutor,
            (@Nullable UiModel.ItemModel before, @Nullable UiModel.ItemModel after) -> {
                if (after != null && (before == null
                        || before.item.label.charAt(0) != after.item.label.charAt(0))) {
                    // separator - after is first item that starts with its first letter
                    return new UiModel.SeparatorModel(
                            Character.toUpperCase(after.item.label.charAt(0)));
                } else {
                    // no separator - either end of list, or first
                    // letters of items are the same
                    return null;
                }
            });
});

public class UiModel {
    static class ItemModel extends UiModel {
        public Item item;
        ItemModel(Item item) {
            this.item = item;
        }
    }
    static class SeparatorModel extends UiModel {
        public char character;
        SeparatorModel(char character) {
            this.character = character;
        }
    }
}

public final @NonNull PagingData<@NonNull R> <T extends Object, R extends Object> PagingDataTransforms.map(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Executor executor,
    @NonNull Function1<@NonNull T, @NonNull R> transform
)

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

public final @NonNull PagingData<@NonNull T> <T extends Object> PagingRx.filterAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Function1<@NonNull T, @NonNull Single<@NonNull Boolean>> predicate
)

Returns a PagingData containing only elements matching the given predicate.

public final @NonNull PagingData<@NonNull T> <T extends Object> PagingRx.filterAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Function1<@NonNull T, @NonNull Single<@NonNull Boolean>> predicate
)

Returns a PagingData containing only elements matching the given predicate.

public final @NonNull PagingData<@NonNull R> <T extends Object, R extends Object> PagingRx.flatMapAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Function1<@NonNull T, @NonNull Single<@NonNull Iterable<@NonNull R>>> transform
)

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

public final @NonNull PagingData<@NonNull R> <T extends Object, R extends Object> PagingRx.flatMapAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Function1<@NonNull T, @NonNull Single<@NonNull Iterable<@NonNull R>>> transform
)

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

public final @NonNull PagingData<@NonNull R> <T extends R, R extends Object> PagingRx.insertSeparatorsAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Function2<T, T, @NonNull Maybe<@NonNull R>> generator
)

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.insertSeparators
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().uppercaseChar().toString()
            } else {
                // no separator - either end of list, or first letters of before/after are the same
                null
            }
        }.subscribeOn(Schedulers.computation())
    }
}

import androidx.paging.insertSeparators
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().uppercaseChar())
                } else {
                    // no separator - either end of list, or first letters of before/after are the same
                    null
                }
            }.subscribeOn(Schedulers.computation())
        }
}

public final @NonNull PagingData<@NonNull R> <T extends R, R extends Object> PagingRx.insertSeparatorsAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Function2<T, T, @NonNull Maybe<@NonNull R>> generator
)

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.insertSeparators
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().uppercaseChar().toString()
            } else {
                // no separator - either end of list, or first letters of before/after are the same
                null
            }
        }.subscribeOn(Schedulers.computation())
    }
}

import androidx.paging.insertSeparators
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().uppercaseChar())
                } else {
                    // no separator - either end of list, or first letters of before/after are the same
                    null
                }
            }.subscribeOn(Schedulers.computation())
        }
}

public final @NonNull PagingData<@NonNull R> <T extends Object, R extends Object> PagingRx.mapAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Function1<@NonNull T, @NonNull Single<@NonNull R>> transform
)

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

public final @NonNull PagingData<@NonNull R> <T extends Object, R extends Object> PagingRx.mapAsync(
    @NonNull PagingData<@NonNull T> receiver,
    @NonNull Function1<@NonNull T, @NonNull Single<@NonNull R>> transform
)

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