You can use the APIs provided by the **mediaLibrary** module to create and delete an album and obtain images in the album.
> **NOTE**
>
> Before developing features, read [MediaLibrary Overview](medialibrary-overview.md) to learn how to obtain a **MediaLibrary** instance and request the permissions to call the APIs of **MediaLibrary**.
To ensure the application running efficiency, most **MediaLibrary** API calls are asynchronous, and both callback and promise modes are provided for these APIs. The following code samples use the promise mode. For details about the APIs, see [MediaLibrary API Reference](../reference/apis/js-apis-medialibrary.md).
## Obtaining Images and Videos in an Album
You can obtain images and videos in an album in either of the following ways:
- Call [MediaLibrary.getFileAssets](../reference/apis/js-apis-medialibrary.md#getfileassets7-1) with an album specified to obtain the media assets. For details, see [Querying Media Assets with the Specified Album Name](medialibrary-resource-guidelines#querying-media-assets-with-the-specified-album-name).
- Call [Album.getFileAssets](../reference/apis/js-apis-medialibrary.md#getfileassets7-3) to obtain an **Album** instance, so as to obtain the media assets in it. For details, see [Obtaining Images and Videos in an Album](medialibrary-resource-guidelines#obtaining-images-and-videos-in-an-album).
## Creating an Album
You can use [MediaLibrary.createAsset](../reference/apis/js-apis-medialibrary.md#createasset8-1), with the relative path set, to create an album while adding a media asset to the album. The relative path is the album name.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.WRITE_MEDIA**.
The following describes how to create an album named **myAlbum**.
**How to Develop**
1. Call **getPublicDirectory** to obtain the public directory that stores files of a certain type.
For details about the operation, see [Obtaining a Public Directory](medialibrary-filepath-guidelines.md#obtaining-a-public-directory).
2. Call **createAsset** to create an image, with the relative path set to **path + 'myAlbum/'**.
This operation creates an album and adds an image to it.
Renaming modifies the **FileAsset.albumName** attribute of the album, that is, the album name. After the modification, call [Album.commitModify](../reference/apis/js-apis-medialibrary.md#commitmodify8-3) to commit the modification to the database.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.WRITE_MEDIA**.
The following describes how to rename the album **newAlbum**.
**How to Develop**
1. Create a retrieval condition for obtaining the target album.
2. Call **getAlbums** to obtain the album list.
3. Rename the album **newAlbum**.
4. Call **Album.commitModify** to commit the modification of the attributes to the database.
User data on OpenHarmony is managed by the **mediaLibrary** module in a unified manner. You can use the APIs provided by this module to access and operate the user data.
> **NOTE**
>
> Before developing features, read [MediaLibrary Overview](medialibrary-overview.md) to learn how to obtain a **MediaLibrary** instance and request the permissions to call the APIs of **MediaLibrary**.
To ensure the application running efficiency, most **MediaLibrary** API calls are asynchronous, and both callback and promise modes are provided for these APIs. The following code samples use the promise mode. For details about the APIs, see [MediaLibrary API Reference](../reference/apis/js-apis-medialibrary.md).
## File Formats Supported by Public Directories
Before using file paths for development, learn the file formats supported by each public directory.
> **CAUTION**
>
> The following table lists only the file types that can be identified by the system. In your application development, pay attention to the file formats supported by the corresponding interfaces. <br> For example, only .jpeg and .webp can be used for image encoding, and only .jpg, .png, .gif, .bmp, .webp, and .raw can be used for image decoding.
| Directory | Directory Type | Media Type | Description | Supported File Format |
| Camera/ | DIR_CAMERA | VIDEO and IMAGE | Directory for storing images and videos taken by the camera. Videos and images can be stored in this directory and its subdirectories.| .bmp / .bm / .gif / .jpg /. jpeg / .jpe / .png / .webp / .raw / .svg / .heif / .mp4 / .3gp / .mpg / .mov / .webm / .mkv |
| Videos/ | DIR_VIDEO | VIDEO | Dedicated video directory. Only videos can be stored in this directory and its subdirectories.| .mp4 / .3gp / .mpg / .mov / .webm / .mkv |
| Pictures/ | DIR_IMAGE | IMAGE | Dedicated image directory. Only images can be stored in this directory and its subdirectories.| .bmp / .bm / .gif / .jpg /. jpeg / .jpe / .png / .webp / .raw / .svg / .heif |
| Audios/ | DIR_AUDIO | AUDIO |Dedicated audio directory. Only audio files can be stored in this directory and its subdirectories.| .aac/.mp3/.flac/.wav/.ogg |
| Documents/ | DIR_DOCUMENTS | FILE |Dedicated file directory. Only files except audios, images, and videos can be stored in this directory and its subdirectories.| - |
| Download/ | DIR_DOWNLOAD | ALLTYPE |Directory for storing downloaded files. The types of files in this directory and its subdirectories are not restricted.| - |
## Obtaining a Public Directory
Different types of files are stored in different public directories. You can call [getPublicDirectory](../reference/apis/js-apis-medialibrary.md#getpublicdirectory8-1) to obtain the public directory that stores files of a certain type.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.READ_MEDIA**.
The following describes how to obtain the public directory that stores camera files.
## Copying Files Between the Application Sandbox and the Public Directory
OpenHarmony provides the application sandbox to minimize the leakage of application data and user privacy information.
Users can access files stored in the public directories through the system applications **Files** and **Gallery**. However, files in the application sandbox can be accessed only by the application itself.
### Copying a File
You can call [mediaLibrary.FileAsset.open](../reference/apis/js-apis-medialibrary.md#open8-1) to open a file in a public directory.
You can call [fileio.open](../reference/apis/js-apis-fileio.md#fileioopen7) to open a file in the application sandbox. The sandbox directory can be accessed only through the application context.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.WRITE_MEDIA**.
- You have imported the module [@ohos.fileio](../reference/apis/js-apis-fileio.md) in addition to @ohos.multimedia.mediaLibrary.
**How to Develop**
1. Call [Context.getFilesDir](../reference/apis/js-apis-Context.md#contextgetfilesdir) to obtain the directory of the application sandbox.
2. Call **MediaLibrary.getFileAssets** and **FetchFileResult.getFirstObject** to obtain the first file in the result set of the public directory.
3. Call **fileio.open** to open the file in the sandbox.
4. Call **fileAsset.open** to open the file in the public directory.
5. Call **fileio.copyfile** to copy the file.
6. Call **fileAsset.close** and **fileio.close** to close the file.
**Example 1: Copying Files from the Public Directory to the Sandbox**
console.log('content read from public file: ',content_pub);
}
```
### Reading and Writing a File
You can use **FileAsset.open** and **FileAsset.close** of [mediaLibrary](../reference/apis/js-apis-medialibrary.md) to open and close a file, and use **fileio.read** and **fileio.write** of [fileio](../reference/apis/js-apis-fileio.md) to read and write a file.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.WRITE_MEDIA**.
- You have imported the module [@ohos.fileio](../reference/apis/js-apis-fileio.md) in addition to @ohos.multimedia.mediaLibrary.
The **mediaLibrary** module provides APIs for you to access and modify media files.
- You can manage [media assets (audios, videos, image, and files)](medialibrary-resource-guidelines.md) as follows:
- Query media assets.
- Obtain an image or a video.
- Obtain the thumbnail of an image or a video.
- Create a media asset.
- Rename a media asset.
- Move a media asset to the recycle bin.
- You can manage [file paths](medialibrary-filepath-guidelines.md) as follows:
- Obtain the public directory that stores files of a certain type.
- Copy files between the application sandbox and the public directory.
- Read and write a file.
- You can manage [albums](medialibrary-album-guidelines.md) as follows:
- Obtain images and videos in an album.
- Create an album.
- Rename an album.
> **NOTE**
>
> This development guide applies only to the stage model (available from API version 9).
To access and modify personal media data, an application must obtain a **MediaLibrary** instance and request the media asset read and write permissions from the user.
Before using the **MediaLibrary** APIs to develop features, you must learn how to:
-[Obtain a MediaLibrary Instance](#obtaining-a-medialibrary-instance)
-[Request Permissions](#requesting-permissions)
## Obtaining a MediaLibrary Instance
An application must call [getMediaLibrary](../reference/apis/js-apis-medialibrary.md#medialibrarygetmedialibrary8) to obtain a **MediaLibrary** instance based on the application context. Through this instance, the application can access and modify personal media data (such as audios, videos, images, and files).
**How to Develop**
1. Import the **mediaLibrary** module.
2. Call **getContext** to obtain the application context.
To read and write a **MediaLibrary** instance, you must have the required permissions, as described in the table below. Before requesting the permissions, ensure that the [basic principles for permission management](../security/accesstoken-overview.md#basic-principles-for-permission-management) are met.
| ohos.permission.READ_MEDIA | Allows an application to read media files from the user's external storage.| user_grant |
| ohos.permission.WRITE_MEDIA | Allows an application to read media files from and write media files into the user's external storage.| user_grant |
| ohos.permission.MEDIA_LOCATION | Allows an application to access geographical locations in the user's media file.| user_grant |
After configuring the permissions in the **module.json5** file, the application must call [Context.requestPermissionsFromUser](../reference/apis/js-apis-ability-context.md#abilitycontextrequestpermissionsfromuser) to check for the required permissions and if they are not granted, request the permissions from the user by displaying a dialog box.
> **NOTE**<br>Even if the user has granted a permission, the application must check for the permission before calling an API protected by the permission. It should not persist the permission granted status, because the user can revoke the permission through the system application **Settings**.
**How to Develop**
1. Declare the permissions in the **module.json5** file. Add the **requestPermissions** tag under **module** in the file, and set the tag based on the project requirements. For details about the tag, see [Guide for Requesting Permissions from User](../security/accesstoken-guidelines.md).
```json
{
"module":{
"requestPermissions":[
{
"name":"ohos.permission.MEDIA_LOCATION",
"reason":"$string:reason",
"usedScene":{
"abilities":[
"MainAbility"
],
"when":"always"
}
},
{
"name":"ohos.permission.READ_MEDIA",
"reason":"$string:reason",
"usedScene":{
"abilities":[
"MainAbility"
],
"when":"always"
}
},
{
"name":"ohos.permission.WRITE_MEDIA",
"reason":"$string:reason",
"usedScene":{
"abilities":[
"MainAbility"
],
"when":"always"
}
}
]
}
}
```
2. Call **requestPermissionsFromUser** to check for the required permissions and if they are not granted, request the permissions from the user by displaying a dialog box.
Your applications can use the APIs provided by the **mediaLibrary** module to perform operations on media assets such as audios, videos, images, and files.
> **NOTE**
>
> Before developing features, read [MediaLibrary Overview](medialibrary-overview.md) to learn how to obtain a **MediaLibrary** instance and request the permissions to call the APIs of **MediaLibrary**.
To ensure the application running efficiency, most **MediaLibrary** API calls are asynchronous, and both callback and promise modes are provided for these APIs. The following code samples use the promise mode. For details about the APIs, see [MediaLibrary API Reference](../reference/apis/js-apis-medialibrary.md).
## Querying Media Assets
You can query media assets by condition such as the media type, date, or album name.
To do so, call [MediaLibrary.getFileAssets](../reference/apis/js-apis-medialibrary.md#getfileassets7-1), with a **MediaFetchOptions** object passed in to specify the conditions. In this object, **MediaFetchOptions.selections** are the retrieval conditions, and the enumerated values of **FileKey** are used as the column names of the conditions; **MediaFetchOptions.selectionArgs** are the values of the conditions. You can also specify **order** (sorting mode of the search result), **uri** (file URI), and **networkId** (network ID of the registered device) as the conditions.
To obtain the object at the specified position (for example, the first, the last, or with the specified index) in the result set, call [FetchFileResult](../reference/apis/js-apis-medialibrary.md#fetchfileresult7). In this section, **getNextObject** is used cyclically to obtain all media assets in the result set.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.READ_MEDIA**.
### Querying Media Assets with the Specified Media Type
The following describes how to obtain images.
**How to Develop**
To specify the media type as the retrieval condition, set **selections** to **FileKey.MEDIA_TYPE**.
To specify the image as the media type, set **selectionArgs** to **MediaType.IMAGE**.
The following describes how to obtain media assets that are added on the specified date. You can also use the modification date and shooting date as the retrieval conditions.
To specify the date when the files are added as the retrieval condition, set **selections** to **FileKey.DATE_ADDED**.
To specify the date 2022-8-5, set **selectionArgs** to **2022-8-5**.
The following describes how to query images and sort them in descending order by the date when they are added. You can also sort them in ascending order.
To sort files in descending order by the date when they are added, set **order** to **FileKey.DATE_ADDED + " DESC"**.
You can obtain media assets in an album in either of the following ways:
- Call [MediaLibrary.getFileAssets](../reference/apis/js-apis-medialibrary.md#getfileassets7-1) with an album specified, as described in [Querying Media Assets with the Specfied Album Name](#querying-media-assets-with-the-specified-album-name).
- Call [Album.getFileAssets](../reference/apis/js-apis-medialibrary.md#getfileassets7-3) to obtain an **Album** instance, so as to obtain the media assets in it.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.READ_MEDIA**.
**How to Develop**
The following describes how to obtain videos in an album named **New Album 1**.
1. Create a retrieval condition for obtaining the target **Album** instance.
```ts
letfileKeyObj=mediaLibrary.FileKey;
letAlbumNoArgsFetchOp={
selections:fileKeyObj.ALBUM_NAME+'= ?',
selectionArgs:['New Album 1']
}
```
2. Create a retrieval condition for obtaining videos in the target album.
```ts
letfileKeyObj=mediaLibrary.FileKey;
letimageType=mediaLibrary.MediaType.VIDEO;
letimagesFetchOp={
selections:fileKeyObj.MEDIA_TYPE+'= ?',
selectionArgs:[imageType.toString()],
}
```
3. Call **Album.getFileAssets** to obtain the videos in the target album.
You can call [FileAsset.getThumbnail](../reference/apis/js-apis-medialibrary.md#getthumbnail8-2) with the thumbnail size passed in to obtain the thumbnail of an image or a video. Thumbnails are usually displayed on the UI.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.READ_MEDIA**.
### Obtaining the Thumbnail of an Image
Your application may need to obtain the thumbnail of an image for preview purposes.
The following describes how to obtain the thumbnail (size: 720 x 720) of the first image in the album.
**How to Develop**
1. Create a retrieval condition for obtaining images in the target album.
2. Call **getFileAssets** to obtain the images in the target album.
3. Call **getFirstObject** to obtain the first image among all the images obtained.
4. Call **getThumbnail** to obtain the thumbnail of the first image.
console.info("createAsset failed with error:"+err);
});
}
```
## Moving a Media Asset to the Recycle Bin
You can use [FileAsset.trash](../reference/apis/js-apis-medialibrary.md#trash8) to move a media asset to the recycle bin.
By default, files in the recycle bin will be stored for 30 days. During this period, you can set **isTrash** in **trash** to **false** to recover the files from the recycle bin. Application users can also recover the files through the system applications **Files** or **Gallery**.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.WRITE_MEDIA**.
The following describes how to move the first file in the result set to the recycle bin.
**How to Develop**
1. Create a retrieval condition for obtaining images in the target album.
2. Call **getFileAssets** to obtain the images in the target album.
3. Call **getFirstObject** to obtain the first image among all the images obtained.
4. Call **trash** to move the first image to the recycle bin.
Renaming modifies the **FileAsset.displayName** attribute of a file, that is, the displayed file name, including the file name extension.
After the modification, call [FileAsset.commitModify](../reference/apis/js-apis-medialibrary.md#commitmodify8-1) to commit the modification to the database.
Before renaming a file, you must call [FetchFileResult](../reference/apis/js-apis-medialibrary.md#fetchfileresult7) to obtain the file.
**Prerequisites**
- You have obtained a **MediaLibrary** instance.
- You have granted the permission **ohos.permission.WRITE_MEDIA**.
The following describes how to rename the first file in the result set as **newtitle.text**.
**How to Develop**
1. Create a retrieval condition for obtaining images in the target album.
2. Call **getFileAssets** to obtain the images in the target album.
3. Call **getFirstObject** to obtain the first image among all the images obtained.
4. Rename the image as **newImage.jpg**.
5. Call **FileAsset.commitModify** to commit the modification of the attributes to the database.
