首先，我使用模型类创建了一个工厂，以简化将数据库列表的Map<String, dynamic>元素建模为ContainerItems的过程：

class ContainerItems {
  String Title, time, daytime, iconName;

  ContainerItems({
    required this.Title,
    required this.iconName,
    required this.time,
    required this.daytime,
  });

  factory ContainerItems.fromJson(Map<String, dynamic> json) {
    return ContainerItems(
      Title: json['title'] as String,
      time: json['time'] as String,
      daytime: json['daytime'] as String,
      iconName: json['image'] as String,
    );
  }
}

然后，可以使用此方法从数据库中获取List<ContainerItems>结果：

Future<List<ContainerItems>> methodName() async {
  List<ContainerItems> result = [];

  final documentSnapshot = await FirebaseFirestore.instance
      .collection('messdiary')
      .doc('days')
      .get();

  final documentData = documentSnapshot.data() as Map<String, dynamic>;
  final sundayList = documentData["sunday"] as List;

  sundayList.forEach((element) {
    result.add(ContainerItems.fromJson(element as Map<String, dynamic>));
  });

  return result;
}