| <html devsite="true"> |
| <head> |
| <title>PagingSource</title> |
| {% setvar book_path %}/reference/kotlin/androidx/_book.yaml{% endsetvar %} |
| {% include "_shared/_reference-head-tags.html" %} |
| </head> |
| <body> |
| <div id="metadata-info-block"></div> |
| <h1>PagingSource</h1> |
| <p> |
| <pre>abstract class <a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>, Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>></pre> |
| </p> |
| <div class="devsite-table-wrapper"><devsite-expandable><span class="expand-control jd-sumtable-subclasses">Known direct subclasses |
| <div class="showalways" id="subclasses-direct"><a href="/reference/kotlin/androidx/paging/ListenableFuturePagingSource.html">ListenableFuturePagingSource</a>, <a href="/reference/kotlin/androidx/paging/rxjava2/RxPagingSource.html">RxPagingSource</a>, <a href="/reference/kotlin/androidx/paging/rxjava3/RxPagingSource.html">RxPagingSource</a></div> |
| </span> |
| <div id="subclasses-direct-summary"> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code><a href="/reference/kotlin/androidx/paging/ListenableFuturePagingSource.html">ListenableFuturePagingSource</a></code></td> |
| <td> |
| <p><code><a href="https://guava.dev/releases/18.0/api/docs/package-list/com/google/common/util/concurrent/ListenableFuture.html">ListenableFuture</a></code>-based compatibility wrapper around <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>'s suspending APIs.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code><a href="/reference/kotlin/androidx/paging/rxjava2/RxPagingSource.html">RxPagingSource</a></code></td> |
| <td> |
| <p>Rx-based compatibility wrapper around <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>'s suspending APIs.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code><a href="/reference/kotlin/androidx/paging/rxjava3/RxPagingSource.html">RxPagingSource</a></code></td> |
| <td> |
| <p>Rx-based compatibility wrapper around <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>'s suspending APIs.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| </devsite-expandable> </div> |
| <hr> |
| <p>Base class for an abstraction of pageable static data from some source, where loading pages of data is typically an expensive operation. Some examples of common <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>s might be from network or from a database.</p> |
| <p>An instance of a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> is used to load pages of data for an instance of <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code>.</p> |
| <p>A <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> can grow as it loads more data, but the data loaded cannot be updated. If the underlying data set is modified, a new <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> / <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> pair must be created to represent an updated snapshot of the data.</p> |
| <h3> Loading Pages</h3> |
| <p><code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> queries data from its <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> in response to loading hints generated as the user scrolls in a <code>RecyclerView</code>.</p> |
| <p>To control how and when a <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> queries data from its <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>, see <code><a href="/reference/kotlin/androidx/paging/PagingConfig.html">PagingConfig</a></code>, which defines behavior such as <code><a href="/reference/kotlin/androidx/paging/PagingConfig.html#pageSize()">PagingConfig.pageSize</a></code> and <code><a href="/reference/kotlin/androidx/paging/PagingConfig.html#prefetchDistance()">PagingConfig.prefetchDistance</a></code>.</p> |
| <h3> Updating Data</h3> |
| <p>A <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> / <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> pair is a snapshot of the data set. A new <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> / <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> must be created if an update occurs, such as a reorder, insert, delete, or content update occurs. A <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> must detect that it cannot continue loading its snapshot (for instance, when Database query notices a table being invalidated), and call <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#invalidate()">invalidate</a></code>. Then a new <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> / <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> pair would be created to represent data from the new state of the database query.</p> |
| <h3> Presenting Data to UI</h3> |
| <p>To present data loaded by a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> to a <code>RecyclerView</code>, create an instance of <code><a href="/reference/kotlin/androidx/paging/Pager.html">Pager</a></code>, which provides a stream of <code><a href="/reference/kotlin/androidx/paging/PagingData.html">PagingData</a></code> that you may collect from and submit to a <code><a href="/reference/kotlin/androidx/paging/PagingDataAdapter.html">PagingDataAdapter</a></code>.</p> |
| <pre class="prettyprint">/** |
| * Sample page-keyed PagingSource, which uses Int page number to load pages. |
| * |
| * Loads Items from network requests via Retrofit to a backend service. |
| * |
| * Note that the key type is Int, since we're using page number to load a page. |
| */ |
| class MyPagingSource( |
| val myBackend: MyBackendService |
| ) : PagingSource<Int, Item>() { |
| override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Item> { |
| |
| // Retrofit calls that return the body type throw either IOException for network |
| // failures, or HttpException for any non-2xx HTTP status codes. This code reports all |
| // errors to the UI, but you can inspect/wrap the exceptions to provide more context. |
| return try { |
| // Key may be null during a refresh, if no explicit key is passed into Pager |
| // construction. Use 0 as default, because our API is indexed started at index 0 |
| val pageNumber = params.key ?: 0 |
| |
| // Suspending network load via Retrofit. This doesn't need to be wrapped in a |
| // withContext(Dispatcher.IO) { ... } block since Retrofit's Coroutine |
| // CallAdapter dispatches on a worker thread. |
| val response = myBackend.searchItems(pageNumber) |
| |
| // Since 0 is the lowest page number, return null to signify no more pages should |
| // be loaded before it. |
| val prevKey = if (pageNumber > 0) pageNumber - 1 else null |
| |
| // This API defines that it's out of data when a page returns empty. When out of |
| // data, we return `null` to signify no more pages should be loaded |
| val nextKey = if (response.items.isNotEmpty()) pageNumber + 1 else null |
| LoadResult.Page( |
| data = response.items, |
| prevKey = prevKey, |
| nextKey = nextKey |
| ) |
| } catch (e: IOException) { |
| LoadResult.Error(e) |
| } catch (e: HttpException) { |
| LoadResult.Error(e) |
| } |
| } |
| |
| override fun getRefreshKey(state: PagingState<Int, Item>): Int? { |
| return state.anchorPosition?.let { |
| state.closestPageToPosition(it)?.prevKey?.plus(1) |
| ?: state.closestPageToPosition(it)?.nextKey?.minus(1) |
| } |
| } |
| }</pre> |
| <pre class="prettyprint">/** |
| * Sample item-keyed [PagingSource], which uses String tokens to load pages. |
| * |
| * Loads Items from network requests via Retrofit to a backend service. |
| */ |
| class MyPagingSource( |
| val myBackend: MyBackendService |
| ) : PagingSource<String, Item>() { |
| override suspend fun load(params: LoadParams<String>): LoadResult<String, Item> { |
| // Retrofit calls that return the body type throw either IOException for network |
| // failures, or HttpException for any non-2xx HTTP status codes. This code reports all |
| // errors to the UI, but you can inspect/wrap the exceptions to provide more context. |
| return try { |
| // Suspending network load via Retrofit. This doesn't need to be wrapped in a |
| // withContext(Dispatcher.IO) { ... } block since Retrofit's Coroutine |
| // CallAdapter dispatches on a worker thread. |
| val response = myBackend.searchItems(params.key) |
| LoadResult.Page( |
| data = response.items, |
| prevKey = response.prev, |
| nextKey = response.next |
| ) |
| } catch (e: IOException) { |
| LoadResult.Error(e) |
| } catch (e: HttpException) { |
| LoadResult.Error(e) |
| } |
| } |
| |
| override fun getRefreshKey(state: PagingState<String, Item>): String? { |
| return state.anchorPosition?.let { state.closestItemToPosition(it)?.id } |
| } |
| }</pre> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%">Parameters</th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>></code></td> |
| <td> |
| <p>Type of key which define what data to load. E.g. <code><a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html">Int</a></code> to represent either a page number or item position, or <code><a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html">String</a></code> if your network uses Strings as next tokens returned with each response.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code><Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>></code></td> |
| <td> |
| <p>Type of data loaded in by this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>. E.g., the type of data that will be passed to a <code><a href="/reference/kotlin/androidx/paging/PagingDataAdapter.html">PagingDataAdapter</a></code> to be displayed in a <code>RecyclerView</code>.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%">See also</th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code><a href="/reference/kotlin/androidx/paging/Pager.html">Pager</a></code></td> |
| <td></td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <h2>Summary</h2> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%"><h3>Nested types</h3></th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td> |
| <div><code>sealed class <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.html">PagingSource.LoadParams</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>></code></div> |
| <p>Params for a load request on a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> from <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">PagingSource.load</a></code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <div><code>class <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.Append.html">PagingSource.LoadParams.Append</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>> : <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.html">PagingSource.LoadParams</a></code></div> |
| <p>Params to load a page of data from a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> via <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">PagingSource.load</a></code> to be appended to the end of the list.</p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <div><code>class <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.Prepend.html">PagingSource.LoadParams.Prepend</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>> : <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.html">PagingSource.LoadParams</a></code></div> |
| <p>Params to load a page of data from a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> via <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">PagingSource.load</a></code> to be prepended to the start of the list.</p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <div><code>class <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.Refresh.html">PagingSource.LoadParams.Refresh</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>> : <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.html">PagingSource.LoadParams</a></code></div> |
| <p>Params for an initial load request on a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> from <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">PagingSource.load</a></code> or a refresh triggered by <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#invalidate()">invalidate</a></code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <div><code>sealed class <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.html">PagingSource.LoadResult</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>, Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>></code></div> |
| <p>Result of a load request from <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">PagingSource.load</a></code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <div><code>data class <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.Error.html">PagingSource.LoadResult.Error</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>, Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>> : <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.html">PagingSource.LoadResult</a></code></div> |
| <p>Error result object for <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">PagingSource.load</a></code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <div><code>class <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.Invalid.html">PagingSource.LoadResult.Invalid</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>, Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>> : <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.html">PagingSource.LoadResult</a></code></div> |
| <p>Invalid result object for <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">PagingSource.load</a></code></p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <div><code>data class <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.Page.html">PagingSource.LoadResult.Page</a><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>, Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>> : <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.html">PagingSource.LoadResult</a></code></div> |
| <p>Success result object for <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">PagingSource.load</a></code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <div><code>object <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.Page.Companion.html">PagingSource.LoadResult.Page.Companion</a></code></div> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%"><h3>Public constructors</h3></th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td> |
| <div><code><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>, Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>> <a href="/reference/kotlin/androidx/paging/PagingSource.html#PagingSource()">PagingSource</a>()</code></div> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%"><h3>Public functions</h3></th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code>abstract Key?</code></td> |
| <td> |
| <div><code><a href="/reference/kotlin/androidx/paging/PagingSource.html#getRefreshKey(androidx.paging.PagingState)">getRefreshKey</a>(state: <a href="/reference/kotlin/androidx/paging/PagingState.html">PagingState</a><Key, Value>)</code></div> |
| <p>Provide a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">Key</a></code> used for the initial <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">load</a></code> for the next <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> due to invalidation of this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code><a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a></code></td> |
| <td> |
| <div><code><a href="/reference/kotlin/androidx/paging/PagingSource.html#invalidate()">invalidate</a>()</code></div> |
| <p>Signal the <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> to stop loading.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code>abstract suspend <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.html">PagingSource.LoadResult</a><Key, Value></code></td> |
| <td> |
| <div><code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">load</a>(params: <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.html">PagingSource.LoadParams</a><Key>)</code></div> |
| <p>Loading API for <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code><a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a></code></td> |
| <td> |
| <div><code><a href="/reference/kotlin/androidx/paging/PagingSource.html#registerInvalidatedCallback(kotlin.Function0)">registerInvalidatedCallback</a>(onInvalidatedCallback: () <span style="white-space: nowrap;">-></span> <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a>)</code></div> |
| <p>Add a callback to invoke when the <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> is first invalidated.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code><a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a></code></td> |
| <td> |
| <div><code><a href="/reference/kotlin/androidx/paging/PagingSource.html#unregisterInvalidatedCallback(kotlin.Function0)">unregisterInvalidatedCallback</a>(onInvalidatedCallback: () <span style="white-space: nowrap;">-></span> <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a>)</code></div> |
| <p>Remove a previously added invalidate callback.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%"><h3>Public properties</h3></th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code><a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html">Boolean</a></code></td> |
| <td> |
| <div><code><a href="/reference/kotlin/androidx/paging/PagingSource.html#invalid()">invalid</a></code></div> |
| <p>Whether this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> has been invalidated, which should happen when the data this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> represents changes since it was first instantiated.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code>open <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html">Boolean</a></code></td> |
| <td> |
| <div><code><a href="/reference/kotlin/androidx/paging/PagingSource.html#jumpingSupported()">jumpingSupported</a></code></div> |
| <p><code>true</code> if this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> supports jumping, <code>false</code> otherwise.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code>open <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html">Boolean</a></code></td> |
| <td> |
| <div><code><a href="/reference/kotlin/androidx/paging/PagingSource.html#keyReuseSupported()">keyReuseSupported</a></code></div> |
| <p><code>true</code> if this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> expects to re-use keys to load distinct pages without a call to <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#invalidate()">invalidate</a></code>, <code>false</code> otherwise.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="list"> |
| <h2>Public constructors</h2> |
| <div class="api-item"><a name="PagingSource--"></a><a name="pagingsource"></a> |
| <h3 class="api-name" id="PagingSource()">PagingSource</h3> |
| <pre class="api-signature no-pretty-print"><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>, Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>> <a href="/reference/kotlin/androidx/paging/PagingSource.html#PagingSource()">PagingSource</a>()</pre> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%">Parameters</th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code><Key : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>></code></td> |
| <td> |
| <p>Type of key which define what data to load. E.g. <code><a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html">Int</a></code> to represent either a page number or item position, or <code><a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html">String</a></code> if your network uses Strings as next tokens returned with each response.</p> |
| </td> |
| </tr> |
| <tr> |
| <td width="40%"><code><Value : <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html">Any</a>></code></td> |
| <td> |
| <p>Type of data loaded in by this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>. E.g., the type of data that will be passed to a <code><a href="/reference/kotlin/androidx/paging/PagingDataAdapter.html">PagingDataAdapter</a></code> to be displayed in a <code>RecyclerView</code>.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| </div> |
| <div class="list"> |
| <h2>Public functions</h2> |
| <div class="api-item"><a name="getRefreshKey-androidx.paging.PagingState-"></a><a name="getrefreshkey"></a> |
| <h3 class="api-name" id="getRefreshKey(androidx.paging.PagingState)">getRefreshKey</h3> |
| <pre class="api-signature no-pretty-print">abstract fun <a href="/reference/kotlin/androidx/paging/PagingSource.html#getRefreshKey(androidx.paging.PagingState)">getRefreshKey</a>(state: <a href="/reference/kotlin/androidx/paging/PagingState.html">PagingState</a><Key, Value>): Key?</pre> |
| <p>Provide a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">Key</a></code> used for the initial <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">load</a></code> for the next <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> due to invalidation of this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>. The <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">Key</a></code> is provided to <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">load</a></code> via <code><a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.html#key()">LoadParams.key</a></code>.</p> |
| <p>The <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">Key</a></code> returned by this method should cause <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">load</a></code> to load enough items to fill the viewport <em>around</em> the last accessed position, allowing the next generation to transparently animate in. The last accessed position can be retrieved via <code><a href="/reference/kotlin/androidx/paging/PagingState.html#anchorPosition()">state.anchorPosition</a></code>, which is typically the <em>top-most</em> or <em>bottom-most</em> item in the viewport due to access being triggered by binding items as they scroll into view.</p> |
| <p>For example, if items are loaded based on integer position keys, you can return <code>( (state.anchorPosition ?: 0) - state.config.initialLoadSize / 2).coerceAtLeast(0)</code>.</p> |
| <p>Alternately, if items contain a key used to load, get the key from the item in the page at index <code><a href="/reference/kotlin/androidx/paging/PagingState.html#anchorPosition()">state.anchorPosition</a></code> then try to center it based on <code>state.config.initialLoadSize</code>.</p> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%">Parameters</th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code>state: <a href="/reference/kotlin/androidx/paging/PagingState.html">PagingState</a><Key, Value></code></td> |
| <td> |
| <p><code><a href="/reference/kotlin/androidx/paging/PagingState.html">PagingState</a></code> of the currently fetched data, which includes the most recently accessed position in the list via <code><a href="/reference/kotlin/androidx/paging/PagingState.html#anchorPosition()">PagingState.anchorPosition</a></code>.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%">Returns</th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code>Key?</code></td> |
| <td> |
| <p><code><a href="/reference/kotlin/androidx/paging/PagingSource.html">Key</a></code> passed to <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">load</a></code> after invalidation used for initial load of the next generation. The <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">Key</a></code> returned by <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#getRefreshKey(androidx.paging.PagingState)">getRefreshKey</a></code> should load pages centered around user's current viewport. If the correct <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">Key</a></code> cannot be determined, <code>null</code> can be returned to allow <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">load</a></code> decide what default key to use.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="api-item"><a name="invalidate--"></a><a name="invalidate"></a> |
| <h3 class="api-name" id="invalidate()">invalidate</h3> |
| <pre class="api-signature no-pretty-print">fun <a href="/reference/kotlin/androidx/paging/PagingSource.html#invalidate()">invalidate</a>(): <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a></pre> |
| <p>Signal the <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> to stop loading.</p> |
| <p>This method is idempotent. i.e., If <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#invalidate()">invalidate</a></code> has already been called, subsequent calls to this method should have no effect.</p> |
| </div> |
| <div class="api-item"><a name="load-androidx.paging.PagingSource.LoadParams-"></a><a name="load"></a> |
| <h3 class="api-name" id="load(androidx.paging.PagingSource.LoadParams)">load</h3> |
| <pre class="api-signature no-pretty-print">abstract suspend fun <a href="/reference/kotlin/androidx/paging/PagingSource.html#load(androidx.paging.PagingSource.LoadParams)">load</a>(params: <a href="/reference/kotlin/androidx/paging/PagingSource.LoadParams.html">PagingSource.LoadParams</a><Key>): <a href="/reference/kotlin/androidx/paging/PagingSource.LoadResult.html">PagingSource.LoadResult</a><Key, Value></pre> |
| <p>Loading API for <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>.</p> |
| <p>Implement this method to trigger your async load (e.g. from database or network).</p> |
| </div> |
| <div class="api-item"><a name="registerInvalidatedCallback-kotlin.Function0-"></a><a name="registerinvalidatedcallback"></a> |
| <h3 class="api-name" id="registerInvalidatedCallback(kotlin.Function0)">registerInvalidatedCallback</h3> |
| <pre class="api-signature no-pretty-print">fun <a href="/reference/kotlin/androidx/paging/PagingSource.html#registerInvalidatedCallback(kotlin.Function0)">registerInvalidatedCallback</a>(onInvalidatedCallback: () <span style="white-space: nowrap;">-></span> <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a>): <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a></pre> |
| <p>Add a callback to invoke when the <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> is first invalidated.</p> |
| <p>Once invalidated, a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> will not become valid again.</p> |
| <p>A <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> will only invoke its callbacks once - the first time <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#invalidate()">invalidate</a></code> is called, on that thread.</p> |
| <p>If this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> is already invalid, the provided <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#registerInvalidatedCallback(kotlin.Function0)">onInvalidatedCallback</a></code> will be triggered immediately.</p> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%">Parameters</th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code>onInvalidatedCallback: () <span style="white-space: nowrap;">-></span> <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a></code></td> |
| <td> |
| <p>The callback that will be invoked on thread that invalidates the <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="api-item"><a name="unregisterInvalidatedCallback-kotlin.Function0-"></a><a name="unregisterinvalidatedcallback"></a> |
| <h3 class="api-name" id="unregisterInvalidatedCallback(kotlin.Function0)">unregisterInvalidatedCallback</h3> |
| <pre class="api-signature no-pretty-print">fun <a href="/reference/kotlin/androidx/paging/PagingSource.html#unregisterInvalidatedCallback(kotlin.Function0)">unregisterInvalidatedCallback</a>(onInvalidatedCallback: () <span style="white-space: nowrap;">-></span> <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a>): <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a></pre> |
| <p>Remove a previously added invalidate callback.</p> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%">Parameters</th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code>onInvalidatedCallback: () <span style="white-space: nowrap;">-></span> <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a></code></td> |
| <td> |
| <p>The previously added callback.</p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| </div> |
| <div class="list"> |
| <h2>Public properties</h2> |
| <div class="api-item"><a name="getInvalid()"></a><a name="setInvalid()"></a><a name="getInvalid--"></a><a name="setInvalid--"></a> |
| <h3 class="api-name" id="invalid()">invalid</h3> |
| <pre class="api-signature no-pretty-print">val <a href="/reference/kotlin/androidx/paging/PagingSource.html#invalid()">invalid</a>: <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html">Boolean</a></pre> |
| <p>Whether this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> has been invalidated, which should happen when the data this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> represents changes since it was first instantiated.</p> |
| </div> |
| <div class="api-item"><a name="getJumpingSupported()"></a><a name="setJumpingSupported()"></a><a name="getJumpingSupported--"></a><a name="setJumpingSupported--"></a> |
| <h3 class="api-name" id="jumpingSupported()">jumpingSupported</h3> |
| <pre class="api-signature no-pretty-print">open val <a href="/reference/kotlin/androidx/paging/PagingSource.html#jumpingSupported()">jumpingSupported</a>: <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html">Boolean</a></pre> |
| <p><code>true</code> if this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> supports jumping, <code>false</code> otherwise.</p> |
| <p>Override this to <code>true</code> if pseudo-fast scrolling via jumps is supported.</p> |
| <p>A jump occurs when a <code>RecyclerView</code> scrolls through a number of placeholders defined by <code><a href="/reference/kotlin/androidx/paging/PagingConfig.html#jumpThreshold()">PagingConfig.jumpThreshold</a></code> and triggers a load with <code><a href="/reference/kotlin/androidx/paging/LoadType.html#REFRESH">LoadType</a></code>.</p> |
| <p><code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code>s that support jumps should override <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#getRefreshKey(androidx.paging.PagingState)">getRefreshKey</a></code> to return a <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">Key</a></code> that would load data fulfilling the viewport given a user's current <code><a href="/reference/kotlin/androidx/paging/PagingState.html#anchorPosition()">PagingState.anchorPosition</a></code>.</p> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <colgroup> |
| <col width="40%"> |
| <col> |
| </colgroup> |
| <thead> |
| <tr> |
| <th colspan="100%">See also</th> |
| </tr> |
| </thead> |
| <tbody class="list"> |
| <tr> |
| <td width="40%"><code><a href="/reference/kotlin/androidx/paging/PagingConfig.html#jumpThreshold()">jumpThreshold</a></code></td> |
| <td></td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="api-item"><a name="getKeyReuseSupported()"></a><a name="setKeyReuseSupported()"></a><a name="getKeyReuseSupported--"></a><a name="setKeyReuseSupported--"></a> |
| <h3 class="api-name" id="keyReuseSupported()">keyReuseSupported</h3> |
| <pre class="api-signature no-pretty-print">open val <a href="/reference/kotlin/androidx/paging/PagingSource.html#keyReuseSupported()">keyReuseSupported</a>: <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html">Boolean</a></pre> |
| <p><code>true</code> if this <code><a href="/reference/kotlin/androidx/paging/PagingSource.html">PagingSource</a></code> expects to re-use keys to load distinct pages without a call to <code><a href="/reference/kotlin/androidx/paging/PagingSource.html#invalidate()">invalidate</a></code>, <code>false</code> otherwise.</p> |
| </div> |
| </div> |
| </body> |
| </html> |
