像这样改变你的方法：

Stream<Service> getServicesById(List<String> ids) async* {
  for (String id in ids) {
    final DocumentSnapshot document = await FirebaseFirestore.instance
        .collection('Services')
        .doc(id)
        .get();

    yield Service.fromJson(document.data()!);
  }
}

如果您想立即返回：

Stream<List<Service>> getServicesById(List<String> ids) async* {
  List<Service> services = [];

  for (String id in ids) {
    final DocumentSnapshot document = await FirebaseFirestore.instance
        .collection('Services')
        .doc(id)
        .get();

    if (document.exists) {
      services.add(Service.fromJson(document.data()!));
    }
  }

  // Yield the list of services when the loop is done
  yield services;
}