HarmonyOS如何把图片保存到手机相册

import photoAccessHelper from '@ohos.file.photoAccessHelper'; 
import fs from '@ohos.file.fs'; 
@Entry 
@Component 
struct Index { 
  @State message: string = 'Hello World' 
  build() { 
    Row() { 
      Column() { 
        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" }) 
          } 
        }) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
}

async pickerSave(buffer: ArrayBuffer | string): Promise<void> { 
  const photoSaveOptions = new picker.PhotoSaveOptions(); // 创建文件管理器保存选项实例 
  photoSaveOptions.newFileNames = ['PhotoViewPicker ' + new Date().getTime() + 'jpg'] // 保存文件名（可选） 
  const photoViewPicker = new picker.PhotoViewPicker; 
  photoViewPicker.save(photoSaveOptions) 
  .then(async (photoSvaeResult) => { 
  console.info('PhotoViewPicker.save successfully,photoSvaeResult uri:' + JSON.stringify(photoSvaeResult)); 
  let uri = photoSvaeResult[0]; 
  let file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE); 
  await fs.write(file.fd, buffer); 
  await fs.close(file.fd); 
  promptAction.showToast({ 
    message: $r('app.string.image_request_success'), 
    duration: 2000 
  }) 
}) 
}