求大佬告知如何保存图片到相册

import photoAccessHelper from '@ohos.file.photoAccessHelper';

Image($r('app.media.icon')) 
  .height(300) 
  .width(300)

 SaveButton().onClick(async (_event: ClickEvent, result: SaveButtonOnClickResult) => { 
          if (result == SaveButtonOnClickResult.SUCCESS) { 
            try { 
              const context = getContext(this); 
              let helper = photoAccessHelper.getPhotoAccessHelper(context); 
              // onClick触发后5秒内通过createAsset接口创建图片文件，5秒后createAsset权限收回。 
              let uri = await helper.createAsset(photoAccessHelper.PhotoType.IMAGE, 'jpg'); 
              // 使用uri打开文件，可以持续写入内容，写入过程不受时间限制 
              let file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE); 
              try { 
                context.resourceManager.getMediaContent($r('app.media.startIcon').id, 0) 
                  .then(async value => { 
                    let media = value.buffer; 
                    // 写到媒体库文件中 
                    await fs.write(file.fd, media); 
                    await fs.close(file.fd); 
                    AlertDialog.show({message:'已保存至相册!'}); 
                  }); 
              } 
              catch (err) { 
                console.error("error is "+ JSON.stringify(err)) 
              } 
            } catch (error) { 
              console.error("error is "+ JSON.stringify(error)); 
            } 
          } 
          else { 
            AlertDialog.show({ message: "设置权限失败" }) 
          } 
        })

 "requestPermissions": [ { 
      "name": "\ohos.permission.WRITE_IMAGEVIDEO" 
    }]