Expo MediaLibrary

提供对设备媒体库的访问的库。

Android

iOS

expo-media-library 提供对用户媒体库的访问，允许他们从你的应用访问现有的图片和视频，以及保存新的图片和视频。你还可以订阅对用户媒体库所做的任何更新。

¥expo-media-library provides access to the user's media library, allowing them to access their existing images and videos from your app, as well as save new ones. You can also subscribe to any updates made to the user's media library.

安装

¥Installation

Terminal

- npx expo install expo-media-library

If you are installing this in an existing React Native app (bare workflow), start by installing expo in your project. Then, follow the additional instructions as mentioned by library's README under "Installation in bare React Native projects" section.

app.json/app.config.js 中的配置

¥Configuration in app.json/app.config.js

如果你在项目中使用配置插件（EAS 构建或 npx expo run:[android|ios]），则可以使用其内置的配置插件配置 expo-media-library。该插件允许你配置无法在运行时设置的各种属性，并且需要构建新的应用二进制文件才能生效。

¥You can configure expo-media-library using its built-in config plugin if you use config plugins in your project (EAS Build or npx expo run:[android|ios]). The plugin allows you to configure various properties that cannot be set at runtime and require building a new app binary to take effect.

Are you using this library in a bare React Native app?

了解如何在 expo-media-library 存储库中的安装说明文件中配置原生项目。

¥Learn how to configure the native projects in the installation instructions in the expo-media-library repository.

Example app.json with config plugin

{
  "expo": {
    "plugins": [
      [
        "expo-media-library",
        {
          "photosPermission": "Allow $(PRODUCT_NAME) to access your photos.",
          "savePhotosPermission": "Allow $(PRODUCT_NAME) to save photos.",
          "isAccessMediaLocationEnabled": true
        }
      ]
    ]
  }
}

Configurable properties

Name	Default	Description
`photosPermission`	`"Allow $(PRODUCT_NAME) to access your photos."`	Only for: iOS Sets the iOS `NSPhotoLibraryUsageDescription` permission message in Info.plist.
`savePhotosPermission`	`"Allow $(PRODUCT_NAME) to save photos."`	Only for: iOS Sets the iOS `NSPhotoLibraryAddUsageDescription` permission message in Info.plist.
`isAccessMediaLocationEnabled`	`false`	Only for: Android Sets whether or not to request the `ACCESS_MEDIA_LOCATION` permission on Android.

用法

¥Usage

Fetching albums and displaying assets

import { useState, useEffect } from 'react';
import { Button, Text, SafeAreaView, ScrollView, StyleSheet, Image, View, Platform } from 'react-native';
import * as MediaLibrary from 'expo-media-library';

export default function App() {
  const [albums, setAlbums] = useState(null);
  const [permissionResponse, requestPermission] = MediaLibrary.usePermissions();

  async function getAlbums() {
    if (permissionResponse.status !== 'granted') {
      await requestPermission();
    }
    const fetchedAlbums = await MediaLibrary.getAlbumsAsync({
      includeSmartAlbums: true,
    });
    setAlbums(fetchedAlbums);
  }

  return (
    <SafeAreaView style={styles.container}>
      <Button onPress={getAlbums} title="Get albums" />
      <ScrollView>
        {albums && albums.map((album) => <AlbumEntry album={album} />)}
      </ScrollView>
    </SafeAreaView>
  );
}

function AlbumEntry({ album }) {
  const [assets, setAssets] = useState([]);

  useEffect(() => {
    async function getAlbumAssets() {
      const albumAssets = await MediaLibrary.getAssetsAsync({ album });
      setAssets(albumAssets.assets);
    }
    getAlbumAssets();
  }, [album]);

  return (
    <View key={album.id} style={styles.albumContainer}>
      <Text>
        {album.title} - {album.assetCount ?? 'no'} assets
      </Text>
      <View style={styles.albumAssetsContainer}>
        {assets && assets.map((asset) => (
          <Image source={{ uri: asset.uri }} width={50} height={50} />
        ))}
      </View>
    </View>
  );
}

%%placeholder-start%%const styles = StyleSheet.create({ ... }); %%placeholder-end%%const styles = StyleSheet.create({
  container: {
    flex: 1,
    gap: 8,
    justifyContent: 'center',
    ...Platform.select({
      android: {
        paddingTop: 40,
      },
    }),
  },
  albumContainer: {
    paddingHorizontal: 20,
    marginBottom: 12,
    gap: 4,
  },
  albumAssetsContainer: {
    flexDirection: 'row',
    flexWrap: 'wrap',
  },
});

API

import * as MediaLibrary from 'expo-media-library';

Constants

`MediaLibrary.MediaType`

Type: MediaTypeObject

Possible media types.

`MediaLibrary.SortBy`

Type: SortByObject

Supported keys that can be used to sort getAssetsAsync results.

Hooks

`usePermissions(options)`

Name	Type
options (optional)	`PermissionHookOptions<{ granularPermissions: GranularPermission[], writeOnly: boolean }>`

Check or request permissions to access the media library. This uses both requestPermissionsAsync and getPermissionsAsync to interact with the permissions.

Returns:

[null | PermissionResponse, RequestPermissionMethod<PermissionResponse>, GetPermissionMethod<PermissionResponse>]

Example

const [permissionResponse, requestPermission] = MediaLibrary.usePermissions();

Methods

`MediaLibrary.addAssetsToAlbumAsync(assets, album, copy)`

Name	Type	Description
assets	`AssetRef \| AssetRef[]`	An array of Asset or their IDs.
album	`AlbumRef`	An Album or its ID.
copy (optional)	`boolean`	Android only. Whether to copy assets to the new album instead of move them. Defaults to `true`. Default: `true`

Adds array of assets to the album.

On Android, by default it copies assets from the current album to provided one, however it's also possible to move them by passing false as copyAssets argument.In case they're copied you should keep in mind that getAssetsAsync will return duplicated assets.

Returns:

Promise<boolean>

Returns promise which fulfils with true if the assets were successfully added to the album.

`MediaLibrary.albumNeedsMigrationAsync(album)`

Name	Type	Description
album	`AlbumRef`	An Album or its ID.

Checks if the album should be migrated to a different location. In other words, it checks if the application has the write permission to the album folder. If not, it returns true, otherwise false.

Note: For Android below R, web or iOS, this function always returns false.

Returns:

Promise<boolean>

Returns a promise which fulfils with true if the album should be migrated.

`MediaLibrary.createAlbumAsync(albumName, asset, copyAsset)`

Name	Type	Description
albumName	`string`	Name of the album to create.
asset (optional)	`AssetRef`	An Asset or its ID (required on Android).
copyAsset (optional)	`boolean`	Android Only. Whether to copy asset to the new album instead of move it. Defaults to `true`. Default: `true`

Creates an album with given name and initial asset. The asset parameter is required on Android, since it's not possible to create empty album on this platform. On Android, by default it copies given asset from the current album to the new one, however it's also possible to move it by passing false as copyAsset argument. In case it's copied you should keep in mind that getAssetsAsync will return duplicated asset.

Returns:

Promise<Album>

Newly created Album.

`MediaLibrary.createAssetAsync(localUri)`

Name	Type	Description
localUri	`string`	A URI to the image or video file. It must contain an extension. On Android it must be a local path, so it must start with `file:///`

Creates an asset from existing file. The most common use case is to save a picture taken by Camera. This method requires CAMERA_ROLL permission.

Returns:

Promise<Asset>

A promise which fulfils with an object representing an Asset.

Example

const { uri } = await Camera.takePictureAsync();
const asset = await MediaLibrary.createAssetAsync(uri);

`MediaLibrary.deleteAlbumsAsync(albums, assetRemove)`

Name	Type	Description
albums	`AlbumRef \| AlbumRef[]`	An array of `Album`s or their IDs.
assetRemove (optional)	`boolean`	iOS Only. Whether to also delete assets belonging to given albums. Defaults to `false`. Default: `false`

Deletes given albums from the library. On Android by default it deletes assets belonging to given albums from the library. On iOS it doesn't delete these assets, however it's possible to do by passing true as deleteAssets.

Returns:

Promise<boolean>

Returns a promise which fulfils with true if the albums were successfully deleted from the library.

`MediaLibrary.deleteAssetsAsync(assets)`

Name	Type	Description
assets	`AssetRef \| AssetRef[]`	An array of Asset or their IDs.

Deletes assets from the library. On iOS it deletes assets from all albums they belong to, while on Android it keeps all copies of them (album is strictly connected to the asset). Also, there is additional dialog on iOS that requires user to confirm this action.

Returns:

Promise<boolean>

Returns promise which fulfils with true if the assets were successfully deleted.

`MediaLibrary.getAlbumAsync(title)`

Name	Type	Description
title	`string`	Name of the album to look for.

Queries for an album with a specific name.

Returns:

Promise<Album>

An object representing an Album, if album with given name exists, otherwise returns null.

`MediaLibrary.getAlbumsAsync(namedParameters)`

Name	Type
namedParameters (optional)	`AlbumsOptions`

Queries for user-created albums in media gallery.

Returns:

Promise<Album[]>

A promise which fulfils with an array of Albums. Depending on Android version, root directory of your storage may be listed as album titled "0" or unlisted at all.

`MediaLibrary.getAssetInfoAsync(asset, options)`

Name	Type	Description
asset	`AssetRef`	An Asset or its ID.
options (optional)	`MediaLibraryAssetInfoQueryOptions`	-

Provides more information about an asset, including GPS location, local URI and EXIF metadata.

Returns:

Promise<AssetInfo>

An AssetInfo object, which is an Asset extended by an additional fields.

`MediaLibrary.getAssetsAsync(assetsOptions)`

Name	Type
assetsOptions (optional)	`AssetsOptions`

Fetches a page of assets matching the provided criteria.

Returns:

Promise<PagedInfo<Asset>>

A promise that fulfils with to PagedInfo object with array of Assets.

Only for:

iOS

`MediaLibrary.getMomentsAsync()`

Fetches a list of moments, which is a group of assets taken around the same place and time.

Returns:

Promise<any>

An array of albums whose type is moment.

`MediaLibrary.getPermissionsAsync(writeOnly, granularPermissions)`

Name	Type	Description
writeOnly (optional)	`boolean`	-
granularPermissions (optional)	`GranularPermission[]`	A list of `GranularPermission` values. This parameter will have an effect only on Android API 33 and newer. By default, `expo-media-library` will ask for all possible permissions.

Checks user's permissions for accessing media library.

Returns:

Promise<PermissionResponse>

A promise that fulfils with PermissionResponse object.

`MediaLibrary.isAvailableAsync()`

Returns whether the Media Library API is enabled on the current device.

Returns:

Promise<boolean>

A promise which fulfils with a boolean, indicating whether the Media Library API is available on the current device.

`MediaLibrary.migrateAlbumIfNeededAsync(album)`

Name	Type	Description
album	`AlbumRef`	An Album or its ID.

Moves album content to the special media directories on Android R or above if needed. Those new locations are in line with the Android scoped storage - so your application won't lose write permission to those directories in the future.

This method does nothing if:

app is running on iOS, web or Android below R
app has write permission to the album folder

The migration is possible when the album contains only compatible files types. For instance, movies and pictures are compatible with each other, but music and pictures are not. If automatic migration isn't possible, the function will be rejected. In that case, you can use methods from the expo-file-system to migrate all your files manually.

Why do you need to migrate files?

Android R introduced a lot of changes in the storage system. Now applications can't save anything to the root directory. The only available locations are from the MediaStore API. Unfortunately, the media library stored albums in folders for which, because of those changes, the application doesn't have permissions anymore. However, it doesn't mean you need to migrate all your albums. If your application doesn't add assets to albums, you don't have to migrate. Everything will work as it used to. You can read more about scoped storage in the Android documentation.

Returns:

Promise<void>

A promise which fulfils to void.

`MediaLibrary.presentPermissionsPickerAsync()`

Available only on iOS >= 14. Allows the user to update the assets that your app has access to. The system modal is only displayed if the user originally allowed only limited access to their media library, otherwise this method is a no-op.

Returns:

Promise<void>

A promise that either rejects if the method is unavailable (meaning the device is not running iOS >= 14), or resolves to void.

Note: This method doesn't inform you if the user changes which assets your app has access to. For that information, you need to subscribe for updates to the user's media library using addListener(listener). If hasIncrementalChanges is false, the user changed their permissions.

`MediaLibrary.removeAssetsFromAlbumAsync(assets, album)`

Name	Type	Description
assets	`AssetRef \| AssetRef[]`	An array of Asset or their IDs.
album	`AlbumRef`	An Album or its ID.

Removes given assets from album.

On Android, album will be automatically deleted if there are no more assets inside.

Returns:

Promise<boolean>

Returns promise which fulfils with true if the assets were successfully removed from the album.

`MediaLibrary.removeSubscription(subscription)`

Name	Type
subscription	`Subscription`

Returns:

void

`MediaLibrary.requestPermissionsAsync(writeOnly, granularPermissions)`

Name	Type	Description
writeOnly (optional)	`boolean`	-
granularPermissions (optional)	`GranularPermission[]`	A list of `GranularPermission` values. This parameter will have an effect only on Android API 33 and newer. By default, `expo-media-library` will ask for all possible permissions.

Asks the user to grant permissions for accessing media in user's media library.

Returns:

Promise<PermissionResponse>

A promise that fulfils with PermissionResponse object.

`MediaLibrary.saveToLibraryAsync(localUri)`

Name	Type	Description
localUri	`string`	A URI to the image or video file. It must contain an extension. On Android it must be a local path, so it must start with `file:///`.

Saves the file at given localUri to the user's media library. Unlike createAssetAsync(), This method doesn't return created asset. On iOS 11+, it's possible to use this method without asking for CAMERA_ROLL permission, however then yours Info.plist should have NSPhotoLibraryAddUsageDescription key.

Returns:

Promise<void>

Event Subscriptions

`MediaLibrary.addListener(listener)`

Name	Type	Description
listener	`(event: MediaLibraryAssetsChangeEvent) => void`	A callback that is fired when any assets have been inserted or deleted from the library, or when the user changes which assets they're allowing access to. On Android it's invoked with an empty object. On iOS it's invoked with `MediaLibraryAssetsChangeEvent` object.

Subscribes for updates in user's media library.

Returns:

Subscription

An Subscription object that you can call remove() on when you would like to unsubscribe the listener.

`MediaLibrary.removeAllListeners()`

Removes all listeners.

Returns:

void

Interfaces

`EXPermissionResponse`

An object obtained by permissions get and request functions.

EXPermissionResponse Properties

Name	Type	Description
canAskAgain	`boolean`	Indicates if user can be asked again for specific permission. If not, one should be directed to the Settings app in order to enable/disable the permission.
expires	`PermissionExpiration`	Determines time when the permission expires.
granted	`boolean`	A convenience boolean that indicates if the permission is granted.
status	`PermissionStatus`	Determines the status of the permission.

Types

`Album`

Name	Type	Description
approximateLocation (optional)	`Location`	Only for: iOS Apply only to albums whose type is `'moment'`. Approximated location of all assets in the moment.
assetCount	`number`	Estimated number of assets in the album.
endTime	`number`	Only for: iOS Apply only to albums whose type is `'moment'`. Latest creation timestamp of all assets in the moment.
id	`string`	Album ID.
locationNames (optional)	`string[]`	Only for: iOS Apply only to albums whose type is `'moment'`. Names of locations grouped in the moment.
startTime	`number`	Only for: iOS Apply only to albums whose type is `'moment'`. Earliest creation timestamp of all assets in the moment.
title	`string`	Album title.
type (optional)	`AlbumType`	Only for: iOS The type of the assets album.

`AlbumRef`

Literal Type: multiple types

Acceptable values are: Album | string

`AlbumType`

Literal Type: string

Acceptable values are: 'album' | 'moment' | 'smartAlbum'

`AlbumsOptions`

Name	Type	Description
includeSmartAlbums (optional)	`boolean`	-

`Asset`

Name	Type	Description
albumId (optional)	`string`	Only for: Android Album ID that the asset belongs to.
creationTime	`number`	File creation timestamp.
duration	`number`	Duration of the video or audio asset in seconds.
filename	`string`	Filename of the asset.
height	`number`	Height of the image or video.
id	`string`	Internal ID that represents an asset.
mediaSubtypes (optional)	`MediaSubtype[]`	Only for: iOS An array of media subtypes.
mediaType	`MediaTypeValue`	Media type.
modificationTime	`number`	Last modification timestamp.
uri	`string`	URI that points to the asset. `assets://` (iOS), `file://` (Android)
width	`number`	Width of the image or video.

`AssetInfo`

Type: Asset extended by:

Name	Type	Description
exif (optional)	`object`	EXIF metadata associated with the image.
isFavorite (optional)	`boolean`	Only for: iOS Whether the asset is marked as favorite.
isNetworkAsset (optional)	`boolean`	Only for: iOS This field is available only if flag `shouldDownloadFromNetwork` is set to `false`. Whether the asset is stored on the network (iCloud on iOS).
localUri (optional)	`string`	Local URI for the asset.
location (optional)	`Location`	GPS location if available.
orientation (optional)	`number`	Only for: iOS Display orientation of the image. Orientation is available only for assets whose `mediaType` is `MediaType.photo`. Value will range from 1 to 8, see EXIF orientation specification for more details.

`AssetRef`

Literal Type: multiple types

Acceptable values are: Asset | string

`AssetsOptions`

Name	Type	Description
after (optional)	`AssetRef`	Asset ID of the last item returned on the previous page. To get the ID of the next page, pass `endCursor` as its value.
album (optional)	`AlbumRef`	Album or its ID to get assets from specific album.
createdAfter (optional)	`Date \| number`	`Date` object or Unix timestamp in milliseconds limiting returned assets only to those that were created after this date.
createdBefore (optional)	`Date \| number`	Similarly as `createdAfter`, but limits assets only to those that were created before specified date.
first (optional)	`number`	The maximum number of items on a single page. Default: `20`
mediaType (optional)	`MediaTypeValue[] \| MediaTypeValue`	An array of MediaTypeValues or a single `MediaTypeValue`. Default: `MediaType.photo`
sortBy (optional)	`SortByValue[] \| SortByValue`	An array of `SortByValue`s or a single `SortByValue` value. By default, all keys are sorted in descending order, however you can also pass a pair `[key, ascending]` where the second item is a `boolean` value that means whether to use ascending order. Note that if the `SortBy.default` key is used, then `ascending` argument will not matter. Earlier items have higher priority when sorting out the results. If empty, this method will use the default sorting that is provided by the platform.

Only for:

Android API 33+

`GranularPermission`

Literal Type: string

Determines the type of media that the app will ask the OS to get access to.

Acceptable values are: 'audio' | 'photo' | 'video'

`Location`

Name	Type	Description
latitude	`number`	-
longitude	`number`	-

`MediaLibraryAssetInfoQueryOptions`

Name	Type	Description
shouldDownloadFromNetwork (optional)	`boolean`	Whether allow the asset to be downloaded from network. Only available in iOS with iCloud assets. Default: `true`

`MediaLibraryAssetsChangeEvent`

Name	Type	Description
deletedAssets (optional)	`Asset[]`	Available only if `hasIncrementalChanges` is `true`. Array of `Asset`s that have been deleted from the library.
hasIncrementalChanges	`boolean`	Whether the media library's changes could be described as "incremental changes". `true` indicates the changes are described by the `insertedAssets`, `deletedAssets` and `updatedAssets` values. `false` indicates that the scope of changes is too large and you should perform a full assets reload (eg. a user has changed access to individual assets in the media library).
insertedAssets (optional)	`Asset[]`	Available only if `hasIncrementalChanges` is `true`. Array of `Asset`s that have been inserted to the library.
updatedAssets (optional)	`Asset[]`	Available only if `hasIncrementalChanges` is `true`. Array of `Asset`s that have been updated or completed downloading from network storage (iCloud on iOS).

`MediaSubtype`

Literal Type: string

`MediaTypeObject`

Name	Type	Description
audio	`'audio'`	-
photo	`'photo'`	-
unknown	`'unknown'`	-
video	`'video'`	-

`MediaTypeValue`

Literal Type: string

Acceptable values are: 'audio' | 'photo' | 'video' | 'unknown'

`PagedInfo`

Name	Type	Description
assets	`T[]`	A page of `Asset`s fetched by the query.
endCursor	`string`	ID of the last fetched asset. It should be passed as `after` option in order to get the next page.
hasNextPage	`boolean`	Whether there are more assets to fetch.
totalCount	`number`	Estimated total number of assets that match the query.

`PermissionExpiration`

Literal Type: multiple types

Permission expiration time. Currently, all permissions are granted permanently.

Acceptable values are: 'never' | number

`PermissionHookOptions`

Literal Type: multiple types

Acceptable values are: PermissionHookBehavior | Options

`PermissionResponse`

Type: EXPermissionResponse extended by:

Name Type Description

Name	Type	Description
accessPrivileges (optional)	`'all' \| 'limited' \| 'none'`	Indicates if your app has access to the whole or only part of the photo library. Possible values are: `'all'` if the user granted your app access to the whole photo library `'limited'` if the user granted your app access only to selected photos (only available on Android API 34+ and iOS 14.0+) `'none'` if user denied or hasn't yet granted the permission

accessPrivileges
(optional)

'all' | 'limited' | 'none'

Indicates if your app has access to the whole or only part of the photo library. Possible values are:

'all' if the user granted your app access to the whole photo library
'limited' if the user granted your app access only to selected photos (only available on Android API 34+ and iOS 14.0+)
'none' if user denied or hasn't yet granted the permission

`SortByKey`

Literal Type: string

`SortByObject`

Name	Type	Description
creationTime	`'creationTime'`	-
default	`'default'`	-
duration	`'duration'`	-
height	`'height'`	-
mediaType	`'mediaType'`	-
modificationTime	`'modificationTime'`	-
width	`'width'`	-

`SortByValue`

Literal Type: multiple types

Acceptable values are: [SortByKey, boolean] | SortByKey

`Subscription`

Name	Type	Description
remove	`() => void`	A method to unsubscribe the listener.

¥The following permissions are added automatically through this library's AndroidManifest.xml.

Android Permission	Description
`READ_EXTERNAL_STORAGE`	Allows an application to read from external storage.
`WRITE_EXTERNAL_STORAGE`	Allows an application to write to external storage.

iOS 系统

¥iOS

该库使用以下用法描述键：

¥The following usage description keys are used by this library:

Info.plist Key	Description
`NSPhotoLibraryUsageDescription`	A message that tells the user why the app is requesting access to the user’s photo library.
`NSPhotoLibraryAddUsageDescription`	A message that tells the user why the app is requesting add-only access to the user’s photo library.