在v2中，

In v2, Children: list is used to list a folder's children and to list all children of the root folder, use the alias root for the folderId value.

但是，在迁移到Google Drive API v3 中指出， Children 和 Parents 集合已被删除.改为使用 files.list .

However, it's stated in Migrate to Google Drive API v3 that Children and Parents collections have been removed. Use files.list instead.

以此，尝试在 q 参数中添加 parents 属性.与此相关的 SO帖子可能会有所帮助.

With this, try adding parents property in your q parameter. This related SO post might help.