我尝试从 REST API 加载数据，但我遇到了来自 catch 类型“Null”的消息；不是“Map”类型的子类型

Question

我的代码遇到一些错误，我无法弄清楚，我已经尝试了很多步骤，但它保持静止，我在提供程序中调用的数据正在工作，但在页面中仍然为空，这是代码。有没有办法知道哪个字段返回 null 这是我的模型。

  OrderListResponse orderListResponseFromJson(String str) =>
    OrderListResponse.fromJson(json.decode(str));

class OrderListResponse {
  OrderListResponse({
    this.status,
    this.data,
 });

 String? status;
 Data? data;

factory OrderListResponse.fromJson(Map<String, dynamic> json) =>
  OrderListResponse(
    status: json["status"],
    data: Data.fromJson(json["data"]),
  );

}

class Data {
Data({
this.records,
required this.items,
this.pages,
this.page,
});

int? records;
List<OrderItemList> items;
int? pages;
int? page;

factory Data.fromJson(Map<String, dynamic> json) => Data(
    records: json["records"],
    items: List<OrderItemList>.from(json["items"]
        .map<OrderItemList>((items) => OrderItemList.fromJson(items))),
    pages: json["pages"],
    page: json["page"],
  );
}

class OrderItemList {
 OrderItemList({
 this.id,
 this.orderNumber,
 this.total,
 this.status,
 this.type,
 this.storeId,
 this.shortDescription,
 this.orderRating,
 this.createdAt,
 this.cico,
 this.storeLogoUrl,
});

int? id;
String? orderNumber;
double? total;
Status? status;
Type? type;
int? storeId;
String? shortDescription;
int? orderRating;
DateTime? createdAt;
Cico? cico;
String? storeLogoUrl;

factory OrderItemList.fromJson(Map<String, dynamic> json) => OrderItemList(
    id: json["id"],
    orderNumber: json["orderNumber"],
    total: json["total"].toDouble(),
    status: statusValues.map[json["status"]],
    type: typeValues.map[json["type"]],
    storeId: json["storeId"] == null ? null : json["storeId"],
    shortDescription:
        json["shortDescription"] == null ? null : json["shortDescription"],
    orderRating: json["orderRating"],
    createdAt: DateTime.parse(json["createdAt"]),
    cico: json["cico"] == null ? null : Cico.fromJson(json["cico"]),
    storeLogoUrl:
        json["storeLogoUrl"] == null ? null : json["storeLogoUrl"],
  );

}

class Cico {
 Cico({
 this.type,
 this.currency,
 this.amount,
 this.total,
 });

 String? type;
 String? currency;
 int? amount;
 int? total;

factory Cico.fromJson(Map<String, dynamic> json) => Cico(
    type: json["type"] == null ? null : json["type"],
    currency: json["currency"] == null ? null : json["currency"],
    amount: json["amount"] == null ? null : json["amount"],
    total: json["total"] == null ? null : json["total"],
  );
 }

enum Status { processing, completed, canceled }

final statusValues = EnumValues({
"canceled": Status.canceled,
"completed": Status.completed,
"processing": Status.processing
});

enum Type { delivery }

final typeValues = EnumValues({"delivery": Type.delivery});

class EnumValues<T> {
  Map<String, T> map;
  Map<T, String>? reverseMap;

  EnumValues(this.map);

  Map<T, String> get reverse {
 reverseMap ??= map.map((k, v) => MapEntry(v, k));
 return reverseMap!;
 }

我有一个

REST API 获取数据：

class OrderListProvider {
 HttpHelper httpHelper = HttpHelper()..init(domain: BaseUrlDomain.wingMall);
 Future<List<OrderListResponse>?> getOrderList({required int page}) async {
 try {
  final response =
      await httpHelper.get(EndPoint.orderList, queryParam: {"page": page});
  if (response.statusCode == 200) {
    var res = response.data['data']['items'] as List;
    log("Information response data: $res");
    return res
        .map<OrderListResponse>(
            (element) => OrderListResponse.fromJson(element))
        .toList();
  }
   return null;
  } catch (error) {
  log("Information error: $error");
  rethrow;
 }
}

提供程序，用于从