AsyncPagingDataDiffer

Kotlin |Java

class AsyncPagingDataDiffer<T : Any>

kotlin.Any
↳	androidx.paging.AsyncPagingDataDiffer

Helper class for mapping a PagingData into a RecyclerView.Adapter.

For simplicity, PagingDataAdapter can often be used in place of this class. AsyncPagingDataDiffer is exposed for complex cases, and where overriding PagingDataAdapter to support paging isn't convenient.

Summary

Public constructors
`<init>(diffCallback: DiffUtil.ItemCallback<T>, updateCallback: ListUpdateCallback, mainDispatcher: CoroutineDispatcher = Dispatchers.Main, workerDispatcher: CoroutineDispatcher = Dispatchers.Default)` Helper class for mapping a PagingData into a RecyclerView.Adapter.

Public methods
Unit	`addLoadStateListener(listener: (CombinedLoadStates) -> Unit)` Add a CombinedLoadStates listener to observe the loading state of the current PagingData.
T?	`getItem(@IntRange(0) index: Int)` Get the item from the current PagedList at the specified index.
T?	`peek(@IntRange(0) index: Int)` Returns the presented item at the specified position, without notifying Paging of the item access that would normally trigger page loads.
Unit	`refresh()` Refresh the data presented by this AsyncPagingDataDiffer.
Unit	`removeLoadStateListener(listener: (CombinedLoadStates) -> Unit)` Remove a previously registered CombinedLoadStates listener.
Unit	`retry()` Retry any failed load requests that would result in a LoadState.Error update to this AsyncPagingDataDiffer.
ItemSnapshotList<T>	`snapshot()` Returns a new ItemSnapshotList representing the currently presented items, including any placeholders if they are enabled.
suspend Unit	`submitData(pagingData: PagingData<T>)` Present a PagingData until it is invalidated by a call to refresh or PagingSource.invalidate.
Unit	`submitData(lifecycle: Lifecycle, pagingData: PagingData<T>)` Present a PagingData until it is either invalidated or another call to submitData is made.

Properties
Int	`itemCount` Get the number of items currently presented by this Differ.
Flow<CombinedLoadStates>	`loadStateFlow` A hot Flow of CombinedLoadStates that emits a snapshot whenever the loading state of the current PagingData changes.

Public constructors

<init>

AsyncPagingDataDiffer(
    diffCallback: DiffUtil.ItemCallback<T>, 
    updateCallback: ListUpdateCallback, 
    mainDispatcher: CoroutineDispatcher = Dispatchers.Main, 
    workerDispatcher: CoroutineDispatcher = Dispatchers.Default)

Helper class for mapping a PagingData into a RecyclerView.Adapter.

Public methods

addLoadStateListener

fun addLoadStateListener(listener: (CombinedLoadStates) -> Unit): Unit

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.


val adapter = UserPagingAdapter()
adapter.addLoadStateListener {
    // show a retry button outside the list when refresh hits an error
    retryButton.isVisible = it.refresh is LoadState.Error

    // swipeRefreshLayout displays whether refresh is occurring
    swipeRefreshLayout.isRefreshing = it.refresh is LoadState.Loading

    // show an empty state over the list when loading initially, before items are loaded
    emptyState.isVisible = it.refresh is LoadState.Loading && adapter.itemCount == 0
}

Parameters
listener: (CombinedLoadStates) -> Unit	LoadStates listener to receive updates.

See Also

removeLoadStateListener

getItem

fun getItem(@IntRange(0)