# ItemKeyedDataSource

Artifact: [androidx.paging:paging-common](https://developer.android.com/jetpack/androidx/releases/paging) [View Source](https://cs.android.com/search?q=file:androidx/paging/ItemKeyedDataSource.jvmAndAndroid.kt+class:androidx.paging.ItemKeyedDataSource) Added in [2.0.0](https://developer.android.com/jetpack/androidx/releases/paging#2.0.0) Deprecated in [3.0.0](https://developer.android.com/jetpack/androidx/releases/paging#3.0.0)

*** ** * ** ***


```
public abstract class ItemKeyedDataSource<Key extends Object, Value extends Object> extends DataSource<@NonNull Key, @NonNull Value>
```

<br />

|---|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object.html) |||
| ↳ | [androidx.paging.DataSource](https://developer.android.com/reference/androidx/paging/DataSource)\<@[NonNull](https://developer.android.com/reference/androidx/annotation/NonNull) Key, @[NonNull](https://developer.android.com/reference/androidx/annotation/NonNull) Value\> ||
|   | ↳ | [androidx.paging.ItemKeyedDataSource](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource) |

*** ** * ** ***

> [!CAUTION]
> **This class is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Incremental data loader for paging keyed content, where loaded content uses previously loaded items as input to future loads.

Implement a DataSource using ItemKeyedDataSource if you need to use data from item `N - 1` to load item `N`. This is common, for example, in uniquely sorted database queries where attributes of the item such just before the next query define how to execute it.

The `InMemoryByItemRepository` in the [PagingWithNetworkSample](https://github.com/googlesamples/android-architecture-components/blob/master/PagingWithNetworkSample/README.md) shows how to implement a network ItemKeyedDataSource using [Retrofit](https://square.github.io/retrofit/), while handling swipe-to-refresh, network errors, and retry.

| Parameters |
|---|---|
| `<Key extends https://developer.android.com/reference/java/lang/Object.html>` | Type of data used to query Value types out of the `https://developer.android.com/reference/androidx/paging/DataSource`. |
| `<Value extends https://developer.android.com/reference/java/lang/Object.html>` | Type of items being loaded by the `https://developer.android.com/reference/androidx/paging/DataSource`. |

## Summary

| ### Nested types |
|---|
| `public abstract class https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadCallback<Value extends https://developer.android.com/reference/java/lang/Object.html>` **This class is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `public abstract class https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialCallback<Value extends https://developer.android.com/reference/java/lang/Object.html> extends https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadCallback<@https://developer.android.com/reference/androidx/annotation/NonNull Value>` **This class is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `public class https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialParams<Key extends https://developer.android.com/reference/java/lang/Object.html>` **This class is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `public class https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadParams<Key extends https://developer.android.com/reference/java/lang/Object.html>` **This class is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |

| ### Public constructors |
|---|
| `<Key extends https://developer.android.com/reference/java/lang/Object.html, Value extends https://developer.android.com/reference/java/lang/Object.html> [ItemKeyedDataSource](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#ItemKeyedDataSource())()` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |

| ### Public methods |
|---|---|
| `abstract @https://developer.android.com/reference/androidx/annotation/NonNull Key` | `[getKey](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#getKey(kotlin.Any))(@https://developer.android.com/reference/androidx/annotation/NonNull Value item)` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `abstract void` | `[loadAfter](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#loadAfter(androidx.paging.ItemKeyedDataSource.LoadParams,androidx.paging.ItemKeyedDataSource.LoadCallback))( @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadParams<@https://developer.android.com/reference/androidx/annotation/NonNull Key> params, @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadCallback<@https://developer.android.com/reference/androidx/annotation/NonNull Value> callback )` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `abstract void` | `[loadBefore](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#loadBefore(androidx.paging.ItemKeyedDataSource.LoadParams,androidx.paging.ItemKeyedDataSource.LoadCallback))( @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadParams<@https://developer.android.com/reference/androidx/annotation/NonNull Key> params, @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadCallback<@https://developer.android.com/reference/androidx/annotation/NonNull Value> callback )` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `abstract void` | `[loadInitial](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#loadInitial(androidx.paging.ItemKeyedDataSource.LoadInitialParams,androidx.paging.ItemKeyedDataSource.LoadInitialCallback))( @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialParams<@https://developer.android.com/reference/androidx/annotation/NonNull Key> params, @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialCallback<@https://developer.android.com/reference/androidx/annotation/NonNull Value> callback )` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `final @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource<@https://developer.android.com/reference/androidx/annotation/NonNull Key, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue>` | `<ToValue extends https://developer.android.com/reference/java/lang/Object.html> [map](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#map(androidx.arch.core.util.Function))( @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/arch/core/util/Function<@https://developer.android.com/reference/androidx/annotation/NonNull Value, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue> function )` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `final @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource<@https://developer.android.com/reference/androidx/annotation/NonNull Key, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue>` | `<ToValue extends https://developer.android.com/reference/java/lang/Object.html> [map](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#map(kotlin.Function1))( @https://developer.android.com/reference/androidx/annotation/NonNull Function1<@https://developer.android.com/reference/androidx/annotation/NonNull Value, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue> function )` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `final @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource<@https://developer.android.com/reference/androidx/annotation/NonNull Key, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue>` | `<ToValue extends https://developer.android.com/reference/java/lang/Object.html> [mapByPage](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#mapByPage(androidx.arch.core.util.Function))( @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/arch/core/util/Function<@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/java/util/List.html<@https://developer.android.com/reference/androidx/annotation/NonNull Value>, @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/java/util/List.html<@https://developer.android.com/reference/androidx/annotation/NonNull ToValue>> function )` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |
| `final @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource<@https://developer.android.com/reference/androidx/annotation/NonNull Key, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue>` | `<ToValue extends https://developer.android.com/reference/java/lang/Object.html> [mapByPage](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#mapByPage(kotlin.Function1))( @https://developer.android.com/reference/androidx/annotation/NonNull Function1<@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/java/util/List.html<@https://developer.android.com/reference/androidx/annotation/NonNull Value>, @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/java/util/List.html<@https://developer.android.com/reference/androidx/annotation/NonNull ToValue>> function )` **This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource |

### Inherited methods

From [androidx.paging.DataSource](https://developer.android.com/reference/androidx/paging/DataSource) `void` `@https://developer.android.com/reference/androidx/annotation/AnyThread
[addInvalidatedCallback](https://developer.android.com/reference/androidx/paging/DataSource#addInvalidatedCallback(androidx.paging.DataSource.InvalidatedCallback))(
@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/DataSource.InvalidatedCallback onInvalidatedCallback
)`

**This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource
`void` `@https://developer.android.com/reference/androidx/annotation/AnyThread
[invalidate](https://developer.android.com/reference/androidx/paging/DataSource#invalidate())()`

**This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource
`boolean` `@https://developer.android.com/reference/androidx/annotation/WorkerThread
[isInvalid](https://developer.android.com/reference/androidx/paging/DataSource#isInvalid())()`

**This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource
`void` `@https://developer.android.com/reference/androidx/annotation/AnyThread
[removeInvalidatedCallback](https://developer.android.com/reference/androidx/paging/DataSource#removeInvalidatedCallback(androidx.paging.DataSource.InvalidatedCallback))(
@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/DataSource.InvalidatedCallback onInvalidatedCallback
)`

**This method is deprecated.** ItemKeyedDataSource is deprecated and has been replaced by PagingSource

## Public constructors

### ItemKeyedDataSource

```
public <Key extends Object, Value extends Object> [ItemKeyedDataSource](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#ItemKeyedDataSource())()
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

| Parameters |
|---|---|
| `<Key extends https://developer.android.com/reference/java/lang/Object.html>` | Type of data used to query Value types out of the `https://developer.android.com/reference/androidx/paging/DataSource`. |
| `<Value extends https://developer.android.com/reference/java/lang/Object.html>` | Type of items being loaded by the `https://developer.android.com/reference/androidx/paging/DataSource`. |

## Public methods

### getKey

Added in [2.0.0](https://developer.android.com/jetpack/androidx/releases/paging#2.0.0) Deprecated in [3.0.0](https://developer.android.com/jetpack/androidx/releases/paging#3.0.0)

```
public abstract @NonNull Key [getKey](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#getKey(kotlin.Any))(@NonNull Value item)
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Return a key associated with the given item.

If your ItemKeyedDataSource is loading from a source that is sorted and loaded by a unique integer ID, you would return `item.getID()` here. This key can then be passed to `https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#loadBefore(androidx.paging.ItemKeyedDataSource.LoadParams)` or `https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#loadAfter(androidx.paging.ItemKeyedDataSource.LoadParams)` to load additional items adjacent to the item passed to this function.

If your key is more complex, such as when you're sorting by name, then resolving collisions with integer ID, you'll need to return both. In such a case you would use a wrapper class, such as `Pair<String, Integer>` or, in Kotlin, `data class Key(val name: String, val id: Int)`

| Parameters |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull Value item` | Item to get the key from. |

| Returns |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull Key` | Key associated with given item. |

### loadAfter

Added in [2.0.0](https://developer.android.com/jetpack/androidx/releases/paging#2.0.0) Deprecated in [3.0.0](https://developer.android.com/jetpack/androidx/releases/paging#3.0.0)

```
public abstract void [loadAfter](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#loadAfter(androidx.paging.ItemKeyedDataSource.LoadParams,androidx.paging.ItemKeyedDataSource.LoadCallback))(
    @NonNull ItemKeyedDataSource.LoadParams<@NonNull Key> params,
    @NonNull ItemKeyedDataSource.LoadCallback<@NonNull Value> callback
)
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Load list data after the key specified in `https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadParams#key()`.

It's valid to return a different list size than the page size if it's easier, e.g. if your backend defines page sizes. It is generally preferred to increase the number loaded than reduce.

Data may be passed synchronously during the loadAfter method, or deferred and called at a later time. Further loads going down will be blocked until the callback is called.

If data cannot be loaded (for example, if the request is invalid, or the data would be stale and inconsistent), it is valid to call `https://developer.android.com/reference/androidx/paging/DataSource#invalidate()` to invalidate the data source, and prevent further loading.

| Parameters |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadParams<@https://developer.android.com/reference/androidx/annotation/NonNull Key> params` | Parameters for the load, including the key to load after, and requested size. |
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadCallback<@https://developer.android.com/reference/androidx/annotation/NonNull Value> callback` | Callback that receives loaded data. |

### loadBefore

Added in [2.0.0](https://developer.android.com/jetpack/androidx/releases/paging#2.0.0) Deprecated in [3.0.0](https://developer.android.com/jetpack/androidx/releases/paging#3.0.0)

```
public abstract void [loadBefore](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#loadBefore(androidx.paging.ItemKeyedDataSource.LoadParams,androidx.paging.ItemKeyedDataSource.LoadCallback))(
    @NonNull ItemKeyedDataSource.LoadParams<@NonNull Key> params,
    @NonNull ItemKeyedDataSource.LoadCallback<@NonNull Value> callback
)
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Load list data before the key specified in `https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadParams#key()`.

It's valid to return a different list size than the page size if it's easier, e.g. if your backend defines page sizes. It is generally preferred to increase the number loaded than reduce.

**Note:** Data returned will be prepended just before the key passed, so if you vary size, ensure that the last item is adjacent to the passed key.

Data may be passed synchronously during the loadBefore method, or deferred and called at a later time. Further loads going up will be blocked until the callback is called.

If data cannot be loaded (for example, if the request is invalid, or the data would be stale and inconsistent), it is valid to call `https://developer.android.com/reference/androidx/paging/DataSource#invalidate()` to invalidate the data source, and prevent further loading.

| Parameters |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadParams<@https://developer.android.com/reference/androidx/annotation/NonNull Key> params` | Parameters for the load, including the key to load before, and requested size. |
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadCallback<@https://developer.android.com/reference/androidx/annotation/NonNull Value> callback` | Callback that receives loaded data. |

### loadInitial

Added in [2.0.0](https://developer.android.com/jetpack/androidx/releases/paging#2.0.0) Deprecated in [3.0.0](https://developer.android.com/jetpack/androidx/releases/paging#3.0.0)

```
public abstract void [loadInitial](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#loadInitial(androidx.paging.ItemKeyedDataSource.LoadInitialParams,androidx.paging.ItemKeyedDataSource.LoadInitialCallback))(
    @NonNull ItemKeyedDataSource.LoadInitialParams<@NonNull Key> params,
    @NonNull ItemKeyedDataSource.LoadInitialCallback<@NonNull Value> callback
)
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Load initial data.

This method is called first to initialize a `https://developer.android.com/reference/androidx/paging/PagedList` with data. If it's possible to count the items that can be loaded by the DataSource, it's recommended to pass the loaded data to the callback via the three-parameter `https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialCallback#onResult(kotlin.collections.List,kotlin.Int,kotlin.Int)`. This enables PagedLists presenting data from this source to display placeholders to represent unloaded items.

`https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialParams#requestedInitialKey()` and `https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialParams#requestedLoadSize()` are hints, not requirements, so they may be altered or ignored. Note that ignoring the `requestedInitialKey` can prevent subsequent PagedList/DataSource pairs from initializing at the same location. If your DataSource never invalidates (for example, loading from the network without the network ever signalling that old data must be reloaded), it's fine to ignore the `initialLoadKey` and always start from the beginning of the data set.

| Parameters |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialParams<@https://developer.android.com/reference/androidx/annotation/NonNull Key> params` | Parameters for initial load, including initial key and requested size. |
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource.LoadInitialCallback<@https://developer.android.com/reference/androidx/annotation/NonNull Value> callback` | Callback that receives initial load data. |

### map

```
public final @NonNull ItemKeyedDataSource<@NonNull Key, @NonNull ToValue> <ToValue extends Object> [map](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#map(androidx.arch.core.util.Function))(
    @NonNull Function<@NonNull Value, @NonNull ToValue> function
)
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Applies the given function to each value emitted by the DataSource.

Same as `https://developer.android.com/reference/androidx/paging/DataSource#mapByPage(androidx.arch.core.util.Function)`, but operates on individual items.

| Parameters |
|---|---|
| `<ToValue extends https://developer.android.com/reference/java/lang/Object.html>` | Type of items produced by the new DataSource, from the passed function. |
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/arch/core/util/Function<@https://developer.android.com/reference/androidx/annotation/NonNull Value, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue> function` | Function that runs on each loaded item, returning items of a potentially new type. |

| Returns |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource<@https://developer.android.com/reference/androidx/annotation/NonNull Key, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue>` | A new DataSource, which transforms items using the given function. |

| See also |
|---|---|
| `https://developer.android.com/reference/androidx/paging/DataSource#mapByPage(androidx.arch.core.util.Function)` |   |
| `https://developer.android.com/reference/androidx/paging/DataSource.Factory#map(androidx.arch.core.util.Function)` |   |
| `https://developer.android.com/reference/androidx/paging/DataSource.Factory#mapByPage(androidx.arch.core.util.Function)` |   |

### map

Added in [3.0.0](https://developer.android.com/jetpack/androidx/releases/paging#3.0.0) Deprecated in [3.0.0](https://developer.android.com/jetpack/androidx/releases/paging#3.0.0)

```
public final @NonNull ItemKeyedDataSource<@NonNull Key, @NonNull ToValue> <ToValue extends Object> [map](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#map(kotlin.Function1))(
    @NonNull Function1<@NonNull Value, @NonNull ToValue> function
)
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Applies the given function to each value emitted by the DataSource.

An overload of `https://developer.android.com/reference/androidx/paging/DataSource#map(kotlin.Function1)` that accepts a kotlin function type.

Same as `https://developer.android.com/reference/androidx/paging/DataSource#mapByPage(androidx.arch.core.util.Function)`, but operates on individual items.

| Parameters |
|---|---|
| `<ToValue extends https://developer.android.com/reference/java/lang/Object.html>` | Type of items produced by the new DataSource, from the passed function. |
| `@https://developer.android.com/reference/androidx/annotation/NonNull Function1<@https://developer.android.com/reference/androidx/annotation/NonNull Value, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue> function` | Function that runs on each loaded item, returning items of a potentially new type. |

| Returns |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource<@https://developer.android.com/reference/androidx/annotation/NonNull Key, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue>` | A new DataSource, which transforms items using the given function. |

| See also |
|---|---|
| `https://developer.android.com/reference/androidx/paging/DataSource#mapByPage(androidx.arch.core.util.Function)` |   |
| `https://developer.android.com/reference/androidx/paging/DataSource.Factory#map(androidx.arch.core.util.Function)` |   |

### mapByPage

```
public final @NonNull ItemKeyedDataSource<@NonNull Key, @NonNull ToValue> <ToValue extends Object> [mapByPage](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#mapByPage(androidx.arch.core.util.Function))(
    @NonNull Function<@NonNull List<@NonNull Value>, @NonNull List<@NonNull ToValue>> function
)
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Applies the given function to each value emitted by the DataSource.

Same as `https://developer.android.com/reference/androidx/paging/DataSource#map(androidx.arch.core.util.Function)`, but allows for batch conversions.

| Parameters |
|---|---|
| `<ToValue extends https://developer.android.com/reference/java/lang/Object.html>` | Type of items produced by the new DataSource, from the passed function. |
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/arch/core/util/Function<@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/java/util/List.html<@https://developer.android.com/reference/androidx/annotation/NonNull Value>, @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/java/util/List.html<@https://developer.android.com/reference/androidx/annotation/NonNull ToValue>> function` | Function that runs on each loaded page, returning items of a potentially new type. |

| Returns |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource<@https://developer.android.com/reference/androidx/annotation/NonNull Key, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue>` | A new DataSource, which transforms items using the given function. |

| See also |
|---|---|
| `https://developer.android.com/reference/androidx/paging/DataSource#map(androidx.arch.core.util.Function)` |   |
| `https://developer.android.com/reference/androidx/paging/DataSource.Factory#map(androidx.arch.core.util.Function)` |   |
| `https://developer.android.com/reference/androidx/paging/DataSource.Factory#mapByPage(androidx.arch.core.util.Function)` |   |

### mapByPage

```
public final @NonNull ItemKeyedDataSource<@NonNull Key, @NonNull ToValue> <ToValue extends Object> [mapByPage](https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource#mapByPage(kotlin.Function1))(
    @NonNull Function1<@NonNull List<@NonNull Value>, @NonNull List<@NonNull ToValue>> function
)
```

> [!CAUTION]
> **This method is deprecated.**   
> ItemKeyedDataSource is deprecated and has been replaced by PagingSource, use this instead:
>
> ```
> PagingSource<Key, Value>
> ```

Applies the given function to each value emitted by the DataSource.

An overload of `https://developer.android.com/reference/androidx/paging/DataSource#mapByPage(kotlin.Function1)` that accepts a kotlin function type.

Same as `https://developer.android.com/reference/androidx/paging/DataSource#map(androidx.arch.core.util.Function)`, but allows for batch conversions.

| Parameters |
|---|---|
| `<ToValue extends https://developer.android.com/reference/java/lang/Object.html>` | Type of items produced by the new DataSource, from the passed function. |
| `@https://developer.android.com/reference/androidx/annotation/NonNull Function1<@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/java/util/List.html<@https://developer.android.com/reference/androidx/annotation/NonNull Value>, @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/java/util/List.html<@https://developer.android.com/reference/androidx/annotation/NonNull ToValue>> function` | Function that runs on each loaded page, returning items of a potentially new type. |

| Returns |
|---|---|
| `@https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/paging/ItemKeyedDataSource<@https://developer.android.com/reference/androidx/annotation/NonNull Key, @https://developer.android.com/reference/androidx/annotation/NonNull ToValue>` | A new `https://developer.android.com/reference/androidx/paging/DataSource`, which transforms items using the given function. |

| See also |
|---|---|
| `https://developer.android.com/reference/androidx/paging/DataSource#map(androidx.arch.core.util.Function)` |   |
| `https://developer.android.com/reference/androidx/paging/DataSource.Factory#map(androidx.arch.core.util.Function)` |   |
| `https://developer.android.com/reference/androidx/paging/DataSource.Factory#mapByPage(androidx.arch.core.util.Function)` |   |