MediaLibrary

• Introduction
• Directory Structure
• Usage Guidelines
  • Query AudioAsset
  • Create Album
  • Copy ImageAsset
• Repositories Involved

Introduction

Figure 1 medialibrary architecture

The medialibrary_standard repository provides a set of easy-to-use APIs for getting media file metadata information. MediaLibrary APIs can only be used internally, not exposed to public application currently.

The various capabilities can be categorized as below:

• Query for audio, video and image files metadata information
• Query for image and video albums
• File operations like create, rename, copy and delete media file
• Album operations like create, rename and delete album

Directory Structure

The structure of the repository directory is as follows:

/foundation/multimedia/medialibrary_standard    # Medialibrary code
├── frameworks                                  # Framework code
│   ├── innerkitsimpl                           # Internal Native API implementation
│   │   └── media_library                       # Native MediaLibrary implementation
│   └── kitsimpl                                # External JS API implementation
│       └── medialibrary                        # External MediaLibrary NAPI implementation
├── interfaces                                  # Interfaces
│   ├── innerkits                               # Internal Native APIs
│   └── kits                                    # External JS APIs
├── LICENSE                                     # License file
├── ohos.build                                  # Build file
├── sa_profile                                  # Service configuration profile
└── services                                    # Service implementation

Usage Guidelines

Query AudioAsset

We can use APIs like GetMediaAssets, GetAudioAssets, GetVideoAssets and GetImageAssets to query for different file metadata information. The following steps describe how to use the GetAudioAssets API to obtain audio related metadata.

1. Use GetMediaLibraryClientInstance API to obtain the Medialibrary instance

   IMediaLibraryClient* mediaLibClientInstance = IMediaLibraryClient::GetMediaLibraryClientInstance();
   

2. Set the scanning directory for audio files in selection string. The selection value will be a relative path to a media root directory i.e. "/storage/media/local/files". It will check for audio files recursively in the given directory.

   string selection = "audios/audio1";
   

3. Use the GetAudioAssets API to query for audio files. The input argument selectionArgs does not have any use case currently. The API returns a list of AudioAsset.

   vector<string> selectionArgs;
   vector<unique_ptr<AudioAsset>> audioAssets = mediaLibClientInstance->GetAudioAssets(selection, selectionArgs);
   

4. We can obtain audio metadata for each file from the list.

   for (size_t i = 0; i < audioAssets.size(); i++) {
       cout << audioAssets[i]->uri_ << endl;
       cout << audioAssets[i]->size_ << endl;
       cout << audioAssets[i]->dateAdded_ << endl;
       cout << audioAssets[i]->dateModified_ << endl;
       cout << audioAssets[i]->albumName_ << endl;
       cout << audioAssets[i]->duration_ << endl;
       cout << audioAssets[i]->artist_ << endl;
   }
   

Create Album

MediaLibrary offers APIs for application to perform album operations like create, modify and delete. Below are the steps on how to create a new album.

1. Use GetMediaLibraryInstance API to obtain the Medialibrary instance

   IMediaLibraryClient* mediaLibClientInstance = IMediaLibraryClient::GetMediaLibraryClientInstance();
   

2. Specify the album type. It can be either ASSET_GENERIC_ALBUM, ASSET_IMAGEALBUM or ASSET_VIDEOALBUM.

   AssetType assetType = ASSET_VIDEOALBUM;
   

3. Create a new AlbumAsset object and provide a new album name. Below album "new_video" will get created in the path "/storage/media/local/files/videos".

   AlbumAsset albumAsset;
   albumAsset.albumName_ = "videos/new_video";
   

4. Use CreateMediaAlbumAsset API to create the new album in the device. The return value will be boolean, which states whether the album creation succeeded or failed.

   bool errCode = mediaLibClientInstance->CreateMediaAlbumAsset(assetType, albumAsset);
   

Copy ImageAsset

File operations are supported via APIs like CreateMediaAsset, ModifyMediaAsset, CopyMediaAsset, DeleteMediaAsset. The example below explains the usage of CopyMediaAsset API.

1. Use GetMediaLibraryInstance API to obtain the Medialibrary instance

   IMediaLibraryClient* mediaLibClientInstance = IMediaLibraryClient::GetMediaLibraryClientInstance();
   

2. Specify the asset type. It can be either ASSET_MEDIA, ASSET_IMAGE, ASSET_AUDIO or ASSET_VIDEO.

   AssetType assetType = ASSET_IMAGE;
   

3. Define the source and target ImageAsset. The target asset must specify the new album name where the source asset will be copied.

   MediaAsset srcMediaAsset;
   MediaAsset dstMediaAsset;
   
   srcMediaAsset.name_ = "image1.jpg";
   srcMediaAsset.uri_ = "/storage/media/local/files/images/001/image1.jpg";
   
   dstMediaAsset.albumName_ = "images/new_image";
   

4. Use CopyMediaAsset API to copy the source asset to target asset's album name location. The boolean return value denotes the status of the file operation. The source file "image1.jpg" will get copied to "/storage/media/local/files/images/new_image".

   bool errCode = mediaLibClientInstance->CopyMediaAsset(assetType, srcMediaAsset, dstMediaAsset);
   

Repositories Involved

multimedia/medialibrary_standard