PagingDataAdapter

Artifact: androidx.leanback:leanback-paging

View Source

Added in 1.1.0-alpha11

---

Kotlin |Java

public final class PagingDataAdapter<T extends Object> extends ObjectAdapter

java.lang.Object
↳	androidx.leanback.widget.ObjectAdapter
	↳	androidx.leanback.paging.PagingDataAdapter

---

An ObjectAdapter implemented with an AsyncPagingDataDiffer. It is an analogue of androidx.paging.PagingDataAdapter for leanback widgets.

Parameters
<T extends Object>	Type of the item in the list.

Summary

Public constructors
<T extends Object> PagingDataAdapter(     @NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback,     @NonNull CoroutineDispatcher mainDispatcher,     @NonNull CoroutineDispatcher workerDispatcher ) Constructs an adapter
<T extends Object> PagingDataAdapter(     @NonNull Presenter presenter,     @NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback,     @NonNull CoroutineDispatcher mainDispatcher,     @NonNull CoroutineDispatcher workerDispatcher ) Constructs an adapter
<T extends Object> PagingDataAdapter(     @NonNull PresenterSelector presenterSelector,     @NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback,     @NonNull CoroutineDispatcher mainDispatcher,     @NonNull CoroutineDispatcher workerDispatcher ) Constructs an adapter

Public methods
final void	addLoadStateListener(     @NonNull Function1<@NonNull CombinedLoadStates, Unit> listener ) Add a CombinedLoadStates listener to observe the loading state of the current PagingData.
T	get(int position) Returns the item for the given position.
final @NonNull Flow<@NonNull CombinedLoadStates>	getLoadStateFlow() A hot Flow of CombinedLoadStates that emits a snapshot whenever the loading state of the current PagingData changes.
final T	peek(@IntRange(from = 0) int index) Returns the presented item at the specified position, without notifying Paging of the item access that would normally trigger page loads.
final void	refresh() Refresh the data presented by this PagingDataAdapter.
final void	removeLoadStateListener(     @NonNull Function1<@NonNull CombinedLoadStates, Unit> listener ) Remove a previously registered CombinedLoadStates listener.
final void	retry() Retry any failed load requests that would result in a LoadState.Error update to this
int	size()
final @NonNull ItemSnapshotList<@NonNull T>	snapshot() Returns a new ItemSnapshotList representing the currently presented items, including any placeholders if they are enabled.
final void	submitData(@NonNull PagingData<@NonNull T> pagingData) Present a PagingData until it is invalidated by a call to refresh or PagingSource.invalidate.
final void	submitData(     @NonNull Lifecycle lifecycle,     @NonNull PagingData<@NonNull T> pagingData ) Present a PagingData until it is either invalidated or another call to submitData is made.

Inherited methods

From androidx.leanback.widget.ObjectAdapter long getId(int position) Returns the id for the given position. final @Nullable Presenter getPresenter(@NonNull Object item) Returns the Presenter for the given item from the adapter. final @NonNull PresenterSelector getPresenterSelector() Returns the presenter selector for this ObjectAdapter. final boolean hasStableIds() Returns true if the item ids are stable across changes to the underlying data. boolean isImmediateNotifySupported() Returns true if the adapter pairs each underlying data change with a call to notify and false otherwise. final void notifyChanged() Notifies UI that the underlying data has changed. final void notifyItemMoved(int fromPosition, int toPosition) Notifies UI that item at fromPosition has been moved to toPosition. final void notifyItemRangeChanged(int positionStart, int itemCount) Notifies UI that some items has changed. final void notifyItemRangeChanged(     int positionStart,     int itemCount,     @Nullable Object payload ) Notifies UI that some items has changed. final void notifyItemRangeInserted(int positionStart, int itemCount) Notifies UI that new items has been inserted. final void notifyItemRangeRemoved(int positionStart, int itemCount) Notifies UI that some items that has been removed. void onHasStableIdsChanged() Called when setHasStableIds is called and the status of stable ids has changed. void onPresenterSelectorChanged() Called when setPresenterSelector is called and the PresenterSelector differs from the previous one. final void registerObserver(@NonNull ObjectAdapter.DataObserver observer) Registers a DataObserver for data change notifications. final void setHasStableIds(boolean hasStableIds) Sets whether the item ids are stable across changes to the underlying data. final void setPresenterSelector(@NonNull PresenterSelector presenterSelector) Sets the presenter selector. final void unregisterAllObservers() Unregisters all DataObservers for this ObjectAdapter. final void unregisterObserver(@NonNull ObjectAdapter.DataObserver observer) Unregisters a DataObserver for data change notifications.

Public constructors

PagingDataAdapter

public <T extends Object> PagingDataAdapter(
    @NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback,
    @NonNull CoroutineDispatcher mainDispatcher,
    @NonNull CoroutineDispatcher workerDispatcher
)

Constructs an adapter

Parameters
@NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback	The DiffUtil.ItemCallback instance to compare items in the list.
@NonNull CoroutineDispatcher mainDispatcher	The CoroutineDispatcher to be used for foreground operations
@NonNull CoroutineDispatcher workerDispatcher	The CoroutineDispatcher to be used for computing diff

PagingDataAdapter

public <T extends Object> PagingDataAdapter(
    @NonNull Presenter presenter,
    @NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback,
    @NonNull CoroutineDispatcher mainDispatcher,
    @NonNull CoroutineDispatcher workerDispatcher
)

Constructs an adapter

Parameters
@NonNull Presenter presenter	Presenter
@NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback	The DiffUtil.ItemCallback instance to compare items in the list.
@NonNull CoroutineDispatcher mainDispatcher	The CoroutineDispatcher to be used for foreground operations
@NonNull CoroutineDispatcher workerDispatcher	The CoroutineDispatcher to be used for computing diff

PagingDataAdapter

public <T extends Object> PagingDataAdapter(
    @NonNull PresenterSelector presenterSelector,
    @NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback,
    @NonNull CoroutineDispatcher mainDispatcher,
    @NonNull CoroutineDispatcher workerDispatcher
)

Constructs an adapter

Parameters
@NonNull PresenterSelector presenterSelector	PresenterSelector
@NonNull DiffUtil.ItemCallback<@NonNull T> diffCallback	The DiffUtil.ItemCallback instance to compare items in the list.
@NonNull CoroutineDispatcher mainDispatcher	The CoroutineDispatcher to be used for foreground operations
@NonNull CoroutineDispatcher workerDispatcher	The CoroutineDispatcher to be used for computing diff

Public methods

addLoadStateListener

Added in 1.1.0-alpha11

public final void addLoadStateListener(
    @NonNull Function1<@NonNull CombinedLoadStates, Unit> listener
)

Add a CombinedLoadStates listener to observe the loading state of the current PagingData.

As new PagingData generations are submitted and displayed, the listener will be notified to reflect the current CombinedLoadStates.

Parameters
@NonNull Function1<@NonNull CombinedLoadStates, Unit> listener	CombinedLoadStates listener to receive updates.

See also
removeLoadStateListener

get

Added in 1.1.0-alpha11

public T get(int position)

Returns the item for the given position. It will return null if placeholders are enabled and data is not yet loaded.

getLoadStateFlow

Added in 1.1.0-alpha11

public final @NonNull Flow<@NonNull CombinedLoadStates> getLoadStateFlow()

A hot Flow of CombinedLoadStates that emits a snapshot whenever the loading state of the current PagingData changes.

This flow is conflated, so it buffers the last update to CombinedLoadStates and immediately delivers the current load states on collection.

peek

Added in 1.1.0-alpha11

public final T peek(@IntRange(from = 0) int index)

Returns the presented item at the specified position, without notifying Paging of the item access that would normally trigger page loads.

Parameters
@IntRange(from = 0) int index	Index of the presented item to return, including placeholders.

Returns
T	The presented item at position index, null if it is a placeholder.

refresh

Added in 1.1.0-alpha11

public final void refresh()

Refresh the data presented by this PagingDataAdapter.

refresh triggers the creation of a new PagingData with a new instance of PagingSource to represent an updated snapshot of the backing dataset. If a RemoteMediator is set, calling refresh will also trigger a call to RemoteMediator.load with LoadType REFRESH] to allow RemoteMediator to check for updates to the dataset backing PagingSource.

Note: This API is intended for UI-driven refresh signals, such as swipe-to-refresh. Invalidation due repository-layer signals, such as DB-updates, should instead use PagingSource.invalidate.

See also
invalidate

removeLoadStateListener

Added in 1.1.0-alpha11

public final void removeLoadStateListener(
    @NonNull Function1<@NonNull CombinedLoadStates, Unit> listener
)

Remove a previously registered CombinedLoadStates listener.

Parameters
@NonNull Function1<@NonNull CombinedLoadStates, Unit> listener	Previously registered listener.

See also
addLoadStateListener

retry

Added in 1.1.0-alpha11

public final void retry()

Retry any failed load requests that would result in a LoadState.Error update to this

PagingDataAdapter.

LoadState.Error can be generated from two types of load requests: PagingSource.load returning PagingSource.LoadResult.Error returning RemoteMediator.MediatorResult.Error

size

Added in 1.1.0-alpha11

public int size()

Returns
int	Total number of presented items, including placeholders.

snapshot

Added in 1.1.0-alpha11

public final @NonNull ItemSnapshotList<@NonNull T> snapshot()

Returns a new ItemSnapshotList representing the currently presented items, including any placeholders if they are enabled.

submitData

Added in 1.1.0-alpha11

public final void submitData(@NonNull PagingData<@NonNull T> pagingData)

Present a PagingData until it is invalidated by a call to refresh or PagingSource.invalidate.

This method is typically used when collecting from a Flow produced by Pager. For RxJava or LiveData support, use the non-suspending overload of submitData, which accepts a Lifecycle.

Note: This method suspends while it is actively presenting page loads from a PagingData, until the PagingData is invalidated. Although cancellation will propagate to this call automatically, collecting from a Pager.flow with the intention of presenting the most up-to-date representation of your backing dataset should typically be done using collectLatest.

See also
Pager

submitData

Added in 1.1.0-alpha11

public final void submitData(
    @NonNull Lifecycle lifecycle,
    @NonNull PagingData<@NonNull T> pagingData
)

Present a PagingData until it is either invalidated or another call to submitData is made.

This method is typically used when observing a RxJava or LiveData stream produced by Pager. For Flow support, use the suspending overload of submitData, which automates cancellation via CoroutineScope instead of relying of Lifecycle.

See also
submitData
Pager