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android / platform / tools / dokka-devsite-plugin / c2f2ba9c887aa0cc0def9a7914ce77d8262d6dd5 / . / testData / paging / docs / reference / kotlin / androidx / paging / PageKeyedDataSource.LoadInitialCallback.html
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<h1>PageKeyedDataSource.LoadInitialCallback</h1>
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<pre>abstract class PageKeyedDataSource.LoadInitialCallback</pre>
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<p>Callback for <code><a href="/reference/kotlin/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/kotlin/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/kotlin/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/kotlin/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</code></td>
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<p>Type of data used to query pages.</p>
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<td><code>Value</code></td>
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<p>Type of items being loaded.</p>
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<h2>Summary</h2>
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<th colspan="2"><h3>Public constructors</h3></th>
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<div><code><a href="/reference/kotlin/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#LoadInitialCallback()">LoadInitialCallback</a>()</code></div>
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<th colspan="2"><h3>Public functions</h3></th>
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<td><code>abstract <a href="/reference/kotlin/kotlin/Unit.html">Unit</a></code></td>
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<div><code><a href="/reference/kotlin/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Int,kotlin.Int,kotlin.Any,kotlin.Any)">onResult</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;data:&nbsp;<a href="/reference/kotlin/kotlin/collections/List.html">List</a>&lt;Value&gt;,<br>&nbsp;&nbsp;&nbsp;&nbsp;position:&nbsp;<a href="/reference/kotlin/kotlin/Int.html">Int</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;totalCount:&nbsp;<a href="/reference/kotlin/kotlin/Int.html">Int</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;previousPageKey:&nbsp;Key?,<br>&nbsp;&nbsp;&nbsp;&nbsp;nextPageKey:&nbsp;Key?<br>)</code></div>
<p>Called to pass initial load state from a DataSource.</p>
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<td><code>abstract <a href="/reference/kotlin/kotlin/Unit.html">Unit</a></code></td>
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<div><code><a href="/reference/kotlin/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Any,kotlin.Any)">onResult</a>(data:&nbsp;<a href="/reference/kotlin/kotlin/collections/List.html">List</a>&lt;Value&gt;,&nbsp;previousPageKey:&nbsp;Key?,&nbsp;nextPageKey:&nbsp;Key?)</code></div>
<p>Called to pass loaded data from a DataSource.</p>
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<h2>Public constructors</h2>
<div><a name="LoadInitialCallback--"></a>
<h3 class="api-name" id="LoadInitialCallback()">LoadInitialCallback</h3>
<pre class="api-signature no-pretty-print"><a href="/reference/kotlin/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#LoadInitialCallback()">LoadInitialCallback</a>()</pre>
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<td><code>Key</code></td>
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<p>Type of data used to query pages.</p>
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<td><code>Value</code></td>
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<p>Type of items being loaded.</p>
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<h2>Public functions</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">abstract&nbsp;fun&nbsp;<a href="/reference/kotlin/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Int,kotlin.Int,kotlin.Any,kotlin.Any)">onResult</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;data:&nbsp;<a href="/reference/kotlin/kotlin/collections/List.html">List</a>&lt;Value&gt;,<br>&nbsp;&nbsp;&nbsp;&nbsp;position:&nbsp;<a href="/reference/kotlin/kotlin/Int.html">Int</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;totalCount:&nbsp;<a href="/reference/kotlin/kotlin/Int.html">Int</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;previousPageKey:&nbsp;Key?,<br>&nbsp;&nbsp;&nbsp;&nbsp;nextPageKey:&nbsp;Key?<br>):&nbsp;<a href="/reference/kotlin/kotlin/Unit.html">Unit</a></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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<td><code>data</code></td>
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<p>List of items loaded from the <code><a href="/reference/kotlin/androidx/paging/DataSource.html">DataSource</a></code>. If this is empty, the <code><a href="/reference/kotlin/androidx/paging/DataSource.html">DataSource</a></code> is treated as empty, and no further loads will occur.</p>
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<td><code>position</code></td>
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<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>
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<td><code>totalCount</code></td>
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<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>
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<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">abstract&nbsp;fun&nbsp;<a href="/reference/kotlin/androidx/paging/PageKeyedDataSource.LoadInitialCallback.html#onResult(kotlin.collections.List,kotlin.Any,kotlin.Any)">onResult</a>(data:&nbsp;<a href="/reference/kotlin/kotlin/collections/List.html">List</a>&lt;Value&gt;,&nbsp;previousPageKey:&nbsp;Key?,&nbsp;nextPageKey:&nbsp;Key?):&nbsp;<a href="/reference/kotlin/kotlin/Unit.html">Unit</a></pre>
<p>Called to pass loaded data from a DataSource.</p>
<p>Call this from <code><a href="/reference/kotlin/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>
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<td><code>data</code></td>
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<p>List of items loaded from the <code><a href="/reference/kotlin/androidx/paging/PageKeyedDataSource.html">PageKeyedDataSource</a></code>.</p>
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<td><code>previousPageKey</code></td>
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<p>Key for page before the initial load result, or <code>null</code> if no more data can be loaded before.</p>
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<td><code>nextPageKey</code></td>
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<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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