类似的操作应该可以获取用户列表:

Something like this should you get the list of users:

static Future<int> getUserAmount() async {
  final response = await FirebaseDatabase.instance
      .reference()
      .child("Users")
      .once();
  var users = [];
  reponse.value.forEach((v) => users.add(v));
  print(users);
  return users.length;
}

您可以与 users 一起检查您需要检查的内容，然后返回结果；

You can check with users what you need to check and then return a result;