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| <title>PageKeyedDataSource.LoadInitialCallback</title> |
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| <h1>PageKeyedDataSource.LoadInitialCallback</h1> |
| {% setvar page_path %}androidx/paging/PageKeyedDataSource.LoadInitialCallback.html{% endsetvar %} |
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| <p> |
| <pre>public abstract class PageKeyedDataSource.LoadInitialCallback<Key extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>, Value extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>></pre> |
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| <p>Callback for <code><a href="/reference/androidx/paging/PageKeyedDataSource.html#loadInitial(androidx.paging.PageKeyedDataSource.LoadInitialParams)">loadInitial</a></code> to return data and, optionally, position/count information.</p> |
| <p>A callback can be called only once, and will throw if called again.</p> |
| <p>If you can compute the number of items in the data set before and after the loaded range, call the five parameter <code><a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Int,kotlin.Int,kotlin.Any,kotlin.Any)">onResult</a></code> to pass that information. You can skip passing this information by calling the three parameter <code><a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Int,kotlin.Int,kotlin.Any,kotlin.Any)">onResult</a></code>, either if it's difficult to compute, or if <code><a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialParams.html#placeholdersEnabled()">LoadInitialParams.placeholdersEnabled</a></code> is <code>false</code>, so the positioning information will be ignored.</p> |
| <p>It is always valid for a DataSource loading method that takes a callback to stash the callback and call it later. This enables DataSources to be fully asynchronous, and to handle temporary, recoverable error states (such as a network error that can be retried).</p> |
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| <th colspan="2">Parameters</th> |
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| <td><code><Key extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>></code></td> |
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| <p>Type of data used to query pages.</p> |
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| <td><code><Value extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>></code></td> |
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| <p>Type of items being loaded.</p> |
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| </div> |
| <h2>Summary</h2> |
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| <th colspan="2"><h3>Public constructors</h3></th> |
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| <div><code><Key extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>, Value extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>> <a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#LoadInitialCallback()">LoadInitialCallback</a>()</code></div> |
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| <th colspan="2"><h3>Public methods</h3></th> |
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| <td><code>abstract void</code></td> |
| <td width="100%"> |
| <div><code><a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Int,kotlin.Int,kotlin.Any,kotlin.Any)">onResult</a>(<br> <a href="https://developer.android.com/reference/java/util/List.html">List</a><Value> data,<br> int position,<br> int totalCount,<br> @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key previousPageKey,<br> @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key nextPageKey<br>)</code></div> |
| <p>Called to pass initial load state from a DataSource.</p> |
| </td> |
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| <td><code>abstract void</code></td> |
| <td width="100%"> |
| <div><code><a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Any,kotlin.Any)">onResult</a>(<br> <a href="https://developer.android.com/reference/java/util/List.html">List</a><Value> data,<br> @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key previousPageKey,<br> @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key nextPageKey<br>)</code></div> |
| <p>Called to pass loaded data from a DataSource.</p> |
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| </div> |
| <h2>Public constructors</h2> |
| <div><a name="LoadInitialCallback--"></a> |
| <h3 class="api-name" id="LoadInitialCallback()">LoadInitialCallback</h3> |
| <pre class="api-signature no-pretty-print">public final <Key extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>, Value extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>> <a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#LoadInitialCallback()">LoadInitialCallback</a>()</pre> |
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| <th colspan="2">Parameters</th> |
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| <td><code><Key extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>></code></td> |
| <td width="100%"> |
| <p>Type of data used to query pages.</p> |
| </td> |
| </tr> |
| <tr> |
| <td><code><Value extends @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> <a href="https://developer.android.com/reference/java/lang/Object.html">Object</a>></code></td> |
| <td width="100%"> |
| <p>Type of items being loaded.</p> |
| </td> |
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| </tbody> |
| </table> |
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| </div> |
| <h2>Public methods</h2> |
| <div><a name="onResult(kotlin.collections.List, kotlin.Int, kotlin.Int, kotlin.Any, kotlin.Any)"></a><a name="onResult-kotlin.collections.List-kotlin.Int-kotlin.Int-kotlin.Any-kotlin.Any-"></a> |
| <h3 class="api-name" id="onResult(kotlin.collections.List,kotlin.Int,kotlin.Int,kotlin.Any,kotlin.Any)">onResult</h3> |
| <pre class="api-signature no-pretty-print">public abstract void <a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Int,kotlin.Int,kotlin.Any,kotlin.Any)">onResult</a>(<br> <a href="https://developer.android.com/reference/java/util/List.html">List</a><Value> data,<br> int position,<br> int totalCount,<br> @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key previousPageKey,<br> @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key nextPageKey<br>)</pre> |
| <p>Called to pass initial load state from a DataSource.</p> |
| <p>Call this method from your DataSource's <code>loadInitial</code> function to return data, and inform how many placeholders should be shown before and after. If counting is cheap to compute (for example, if a network load returns the information regardless), it's recommended to pass data back through this method.</p> |
| <p>It is always valid to pass a different amount of data than what is requested. Pass an empty list if there is no more data to load.</p> |
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| <th colspan="2">Parameters</th> |
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| <td><code><a href="https://developer.android.com/reference/java/util/List.html">List</a><Value> data</code></td> |
| <td width="100%"> |
| <p>List of items loaded from the <code><a href="/reference/androidx/paging/DataSource.html">DataSource</a></code>. If this is empty, the <code><a href="/reference/androidx/paging/DataSource.html">DataSource</a></code> is treated as empty, and no further loads will occur.</p> |
| </td> |
| </tr> |
| <tr> |
| <td><code>int position</code></td> |
| <td width="100%"> |
| <p>Position of the item at the front of the list. If there are <code>N</code> items before the items in data that can be loaded from this DataSource, pass <code>N</code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td><code>int totalCount</code></td> |
| <td width="100%"> |
| <p>Total number of items that may be returned from this DataSource. Includes the number in the initial <code>data</code> parameter as well as any items that can be loaded in front or behind of <code>data</code>.</p> |
| </td> |
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| </div> |
| </div> |
| <div><a name="onResult(kotlin.collections.List, kotlin.Any, kotlin.Any)"></a><a name="onResult-kotlin.collections.List-kotlin.Any-kotlin.Any-"></a> |
| <h3 class="api-name" id="onResult(kotlin.collections.List,kotlin.Any,kotlin.Any)">onResult</h3> |
| <pre class="api-signature no-pretty-print">public abstract void <a href="/reference/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Any,kotlin.Any)">onResult</a>(<br> <a href="https://developer.android.com/reference/java/util/List.html">List</a><Value> data,<br> @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key previousPageKey,<br> @<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key nextPageKey<br>)</pre> |
| <p>Called to pass loaded data from a DataSource.</p> |
| <p>Call this from <code><a href="/reference/androidx/paging/PageKeyedDataSource.html#loadInitial(androidx.paging.PageKeyedDataSource.LoadInitialParams)">loadInitial</a></code> to initialize without counting available data, or supporting placeholders.</p> |
| <p>It is always valid to pass a different amount of data than what is requested. Pass an empty list if there is no more data to load.</p> |
| <div class="devsite-table-wrapper"> |
| <table class="responsive"> |
| <thead> |
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| <th colspan="2">Parameters</th> |
| </tr> |
| </thead> |
| <tbody> |
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| <td><code><a href="https://developer.android.com/reference/java/util/List.html">List</a><Value> data</code></td> |
| <td width="100%"> |
| <p>List of items loaded from the <code><a href="/reference/androidx/paging/PageKeyedDataSource.html">PageKeyedDataSource</a></code>.</p> |
| </td> |
| </tr> |
| <tr> |
| <td><code>@<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key previousPageKey</code></td> |
| <td width="100%"> |
| <p>Key for page before the initial load result, or <code>null</code> if no more data can be loaded before.</p> |
| </td> |
| </tr> |
| <tr> |
| <td><code>@<a href="/reference/androidx/annotation/Nullable.html">Nullable</a> Key nextPageKey</code></td> |
| <td width="100%"> |
| <p>Key for page after the initial load result, or <code>null</code> if no more data can be loaded after.</p> |
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