HarmonyOS 录像后，图库里找不到视频

自定义相机视频录制时，视频文件是存在应用的沙箱目录，需要在录制完成后，保存到相册后才可以在图库找到。保存视频到相册可以参考如下方法：

async  videoWriteAlbumExample2(fileUri:string) {
  console.info('createVideoAssetRequestDemo:' + fileUri);
  let context = getContext(this);
  try {
    // 需要确保fileUri对应的资源存在
    let phAccessHelper = photoAccessHelper.getPhotoAccessHelper(context);
    let assetChangeRequest: photoAccessHelper.MediaAssetChangeRequest = photoAccessHelper.MediaAssetChangeRequest.createVideoAssetRequest(context, fileUri);
    await phAccessHelper.applyChanges(assetChangeRequest);
    console.info('apply createVideoAssetRequest successfully');
    promptAction.showToast({
      message: '已保存至相册',
      duration: 2500
    });
  } catch (err) {
    console.error(`createVideoAssetRequestDemo failed with error: ${err.code}, ${err.message}`);
    promptAction.showToast({
      message: '保存失败',
      duration: 2000
    });
  }
}