MediaLibrary Development Overview

The mediaLibrary module provides APIs for you to access and modify media files.

• You can manage media assets (audios, videos, image, and files) 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 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 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. Unless otherwise specified, the MediaLibrary APIs are used in pages/index.ets or custom .ets files of the project code.

Before using the MediaLibrary APIs to develop features, you must learn how to:

• Obtain a MediaLibrary Instance
• Request Permissions

Obtaining a MediaLibrary Instance

An application must call getMediaLibrary 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.
3. Obtain a MediaLibrary instance.

import mediaLibrary from '@ohos.multimedia.mediaLibrary';

const context = getContext(this);
let media = mediaLibrary.getMediaLibrary(context);

Requesting Permissions

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 are met.

After configuring the permissions in the module.json5 file, the application must call abilityAccessCtrl.requestPermissionsFromUser to check for the required permissions and if they are not granted, request the permissions from the user by displaying a dialog box.

NOTE
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.

   {
       "module": {
           "requestPermissions": [
               {
                   "name": "ohos.permission.MEDIA_LOCATION",
                   "reason": "$string:reason",
                   "usedScene": {
                       "abilities": [
                         "EntryAbility"
                       ],
                       "when": "always"
               }
               },
               {
                   "name": "ohos.permission.READ_MEDIA",
                   "reason": "$string:reason",
                   "usedScene": {
                       "abilities": [
                           "EntryAbility"
                       ],
                       "when": "always"
                   }
               },
               {
                   "name": "ohos.permission.WRITE_MEDIA",
                   "reason": "$string:reason",
                   "usedScene": {
                       "abilities": [
                           "EntryAbility"
                       ],
                       "when": "always"
                   }
               }
           ]
       }
   }    

1. In the Ability.ts file, call requestPermissionsFromUser in the onWindowStageCreate callback to check for the required permissions and if they are not granted, request the permissions from the user by displaying a dialog box.

   import UIAbility from '@ohos.app.ability.UIAbility';
   import abilityAccessCtrl, {Permissions} from '@ohos.abilityAccessCtrl';
   
   export default class EntryAbility extends UIAbility {
       onWindowStageCreate(windowStage) {
           let list : Array<Permissions> = ['ohos.permission.READ_MEDIA', 'ohos.permission.WRITE_MEDIA'];
           let permissionRequestResult;
           let atManager = abilityAccessCtrl.createAtManager();
           atManager.requestPermissionsFromUser(this.context, list, (err, result) => {
               if (err) {
                   console.log('requestPermissionsFromUserError: ' + JSON.stringify(err));
               } else {
                   permissionRequestResult=result;
                   console.log('permissionRequestResult: ' + JSON.stringify(permissionRequestResult));
               }    
           });       
       }
   }

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