Media Asset Management

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 to learn how to obtain a MediaLibrary instance and request the permissions to call the APIs of MediaLibrary.

To maximize the application running efficiency, most MediaLibrary API calls are asynchronous in callback or promise mode. The following code samples use the promise mode. For details about the APIs, see MediaLibrary API Reference.

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, 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. 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.

async function example() {
    let fileKeyObj = mediaLibrary.FileKey;
    let fileType = mediaLibrary.MediaType.IMAGE;
    let option = {
        selections: fileKeyObj.MEDIA_TYPE + '= ?',
        selectionArgs: [fileType.toString()],
    };
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    const fetchFileResult = await media.getFileAssets(option);
    for (let i = 0; i < fetchFileResult.getCount(); i++) {
        fetchFileResult.getNextObject((err, fileAsset) => {
        if (err) {
            console.error('Failed ');
            return;
        }
        console.log('fileAsset.displayName ' + i + ': ' + fileAsset.displayName);
        })
    } 
}

Querying Media Assets with the Specified Date

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.

async function example() {
    let fileKeyObj = mediaLibrary.FileKey;
    let option = {
        selections: fileKeyObj.DATE_ADDED + '= ?',
        selectionArgs: ['2022-8-5'],
    };
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    const fetchFileResult = await media.getFileAssets(option);
    for (let i = 0; i < fetchFileResult.getCount(); i++) {
        fetchFileResult.getNextObject((err, fileAsset) => {
        if (err) {
            console.error('Failed ');
            return;
        }
        console.log('fileAsset.displayName ' + i + ': ' + fileAsset.displayName);
        })
    } 
}

Querying Media Assets and Sorting Them

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”.

async function example() {
    let fileKeyObj = mediaLibrary.FileKey;
    let fileType = mediaLibrary.MediaType.IMAGE;
    let option = {
        selections: fileKeyObj.MEDIA_TYPE + '= ?',
        selectionArgs: [fileType.toString()],
        order: fileKeyObj.DATE_ADDED + " DESC",
    };
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    const fetchFileResult = await media.getFileAssets(option);
    for (let i = 0; i < fetchFileResult.getCount(); i++) {
        fetchFileResult.getNextObject((err, fileAsset) => {
        if (err) {
            console.error('Failed ');
            return;
        }
        console.log('fileAsset.displayName ' + i + ': ' + fileAsset.displayName);
        })
    } 
}

Querying Media Assets with the Specified Album Name

The following describes how to query media assets in myAlbum.

To specify the album name as the retrieval condition, set selections to FileKey.ALBUM_NAME.

To specify the album name ‘myAlbum’, set selectionArgs to ‘myAlbum’.

async function example() {
    let fileKeyObj = mediaLibrary.FileKey;
    let fileType = mediaLibrary.MediaType.IMAGE;
    let option = {
        selections: fileKeyObj.ALBUM_NAME + '= ?',
        selectionArgs: ['myAlbum'],
    };
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    const fetchFileResult = await media.getFileAssets(option);
    for (let i = 0; i < fetchFileResult.getCount(); i++) {
        fetchFileResult.getNextObject((err, fileAsset) => {
        if (err) {
            console.error('Failed ');
            return;
        }
        console.log('fileAsset.displayName ' + i + ': ' + fileAsset.displayName);
        })
    } 
}

Obtaining Images and Videos in an Album

You can obtain media assets in an album in either of the following ways:

• Call MediaLibrary.getFileAssets with an album specified, as described in Querying Media Assets with the Specfied Album Name.
• Call Album.getFileAssets 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.

   let fileKeyObj = mediaLibrary.FileKey;
   let AlbumNoArgsFetchOp = {
       selections: fileKeyObj.ALBUM_NAME + '= ?',
       selectionArgs:['New Album 1']
   }

1. Create a retrieval condition for obtaining videos in the target album.

   let fileKeyObj = mediaLibrary.FileKey;
   let imageType = mediaLibrary.MediaType.VIDEO;
   let imagesFetchOp  = {
       selections: fileKeyObj.MEDIA_TYPE + '= ?',
       selectionArgs: [imageType.toString()],
   }

1. Call Album.getFileAssets to obtain the videos in the target album.

Complete sample code:

async function getCameraImagePromise() {
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    let fileKeyObj = mediaLibrary.FileKey;
    let imageType = mediaLibrary.MediaType.IMAGE;
    let imagesFetchOp = {
        selections: fileKeyObj.MEDIA_TYPE + '= ?',
        selectionArgs: [imageType.toString()],
    }
    let AlbumNoArgsFetchOp = {
        selections: fileKeyObj.ALBUM_NAME + '= ?',
        selectionArgs:['New Album 1']
    }

    let albumList = await media.getAlbums(AlbumNoArgsFetchOp);
    if (albumList.length > 0) {
        const album = albumList[0];
        let fetchFileResult = await album.getFileAssets(imagesFetchOp);
        let count = fetchFileResult.getCount();
        console.info("get mediaLibrary IMAGE number", count);
    } else {
        console.info('getAlbum list is: 0');
    }
}

Obtaining the Thumbnail of an Image or a Video

You can call FileAsset.getThumbnail with the thumbnail size passed in to obtain the thumbnail of an image or a video. Your application can use thumbnails to offer a quick preview on images and videos.

Prerequisites

• You have obtained a MediaLibrary instance.
• You have granted the permission ohos.permission.READ_MEDIA.

Obtaining the Thumbnail of an Image

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.

async function getFirstThumbnailPromise() {
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    let fileKeyObj = mediaLibrary.FileKey;
    let imageType = mediaLibrary.MediaType.IMAGE;
    let imagesFetchOp = {
        selections: fileKeyObj.MEDIA_TYPE + '= ?',
        selectionArgs: [imageType.toString()],
    }

    let size = { width: 720, height: 720 };
    const fetchFileResult = await media.getFileAssets(imagesFetchOp);
    if (fetchFileResult != undefined) {
        const asset = await fetchFileResult.getFirstObject();
        asset.getThumbnail(size).then((pixelMap) => {
          pixelMap.getImageInfo().then((info) => {
              console.info('get Thumbnail info: ' + "width: " + info.size.width + " height: " + info.size.height);
          }).catch((err) => {
              console.info("getImageInfo failed with error:" + err);
          });
        }).catch((err) => {
            console.info("getImageInfo failed with error:" + err);
        });
    } else {
        console.info("get image failed with error");
    }
}

Creating a Media Asset

You can call MediaLibrary.createAsset to create a media asset.

Prerequisites

• You have obtained a MediaLibrary instance.
• You have granted the permission ohos.permission.WRITE_MEDIA.
• You have obtained a public directory.

The following describes how to create a file of the MediaType.FILE type.

async function example() {
    let mediaType = mediaLibrary.MediaType.FILE;
    let DIR_DOCUMENTS = mediaLibrary.DirectoryType.DIR_DOCUMENTS;
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    const path = await media.getPublicDirectory(DIR_DOCUMENTS);
    media.createAsset(mediaType, "testFile.text", path).then ((asset) => {
        console.info("createAsset successfully:"+ JSON.stringify(asset));
    }).catch((err) => {
        console.info("createAsset failed with error:"+ err);
    });
}

Moving a Media Asset to the Recycle Bin

You can use FileAsset.trash to move a media asset to the recycle bin.

By default, files in the recycle bin will be stored for 30 days before being permanently removed. During this period, you can set isTrash in trash to false to recover the files. 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.

async function example() {
    let fileKeyObj = mediaLibrary.FileKey;
    let fileType = mediaLibrary.MediaType.FILE;
    let option = {
        selections: fileKeyObj.MEDIA_TYPE + '= ?',
        selectionArgs: [fileType.toString()],
    };
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    const fetchFileResult = await media.getFileAssets(option);
    let asset = await fetchFileResult.getFirstObject();
    if (asset == undefined) {
      console.error('asset not exist');
      return;
    }
    // Void callback.
    asset.trash(true).then(() => {
        console.info("trash successfully");
    }).catch((err) => {
        console.info("trash failed with error: " + err);
    });
}

Renaming a Media Asset

To rename a media asset, modify the FileAsset.displayName attribute (which specifies the displayed file name, including the file name extension) and commit the modification through FileAsset.commitModify.

Before renaming a file, you must obtain the file, for example, by calling FetchFileResult.

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 to the database.

async function example() {
    let fileKeyObj = mediaLibrary.FileKey;
    let fileType = mediaLibrary.MediaType.FILE;
    let option = {
        selections: fileKeyObj.MEDIA_TYPE + '= ?',
        selectionArgs: [fileType.toString()],
    };
    const context = getContext(this);
    let media = mediaLibrary.getMediaLibrary(context);
    const fetchFileResult = await media.getFileAssets(option);
    let asset = await fetchFileResult.getFirstObject();
    if (asset == undefined) {
      console.error('asset not exist');
      return;
    }
    asset.displayName = 'newImage.jpg';
    // Void callback.
    asset.commitModify((err) => {
       if (err) {
           console.error('fileRename Failed ');
           return;
       }
       console.log('fileRename successful.');
    });
}

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