我不明白为什么这个错误类型'Null'不是类型转换中 'int' 类型的子类型

Question

颤振3.3.9•通道稳定•https://github.com/flutter/flutter.git框架•修订b8f7f1f986(有2个语义)•2022年11月23日06:43:51 +0900发动机型号:8f2221fbefTools•Dart 2.18.5•DevTools 2.15.0

你好，致以最良好的问候，我希望你一切都好，我花了最后几个小时试图解决问题标题中的错误，我没有能够，你能给我解释一下解决它的方法吗，我已经附上了我正在使用的模型和请求的响应到一个api，提前非常感谢你

base_response_model.dart

import 'package:json_annotation/json_annotation.dart';
part 'base_response_model.g.dart';
@JsonSerializable()
class BaseResponseModel {
final int page;
@JsonKey(name: 'page_size')
final int pageSize;
final int total;
final int pages;
@JsonKey(name: 'prev_page', defaultValue: 0)
final dynamic prevPage;
@JsonKey(name: 'next_page', defaultValue: 0)
final dynamic nextPage;
BaseResponseModel({
required this.page,
required this.pageSize,
required this.total,
required this.pages,
required this.prevPage,
required this.nextPage,
});
factory BaseResponseModel.fromJson(Map<String, dynamic> json) =>
_$BaseResponseModelFromJson(json);
Map<String, dynamic> toJson() => _$BaseResponseModelToJson(this);
}

get_municipalities_by_province_response_model.dart

import 'package:delivery/app/data/models/andariego/andariego_models/municipality_model.dart';
import 'package:delivery/app/data/models/andariego/andariego_response_models/base_response_model.dart';
import 'package:json_annotation/json_annotation.dart';
part 'get_municipalities_by_province_response_model.g.dart';
@JsonSerializable()
class GetMunicipalitiesByProvinceResponseModel extends BaseResponseModel {
final List<MunicipalityModel> data;
GetMunicipalitiesByProvinceResponseModel({
required super.page,
required super.pageSize,
required super.total,
required super.pages,
required super.prevPage,
required super.nextPage,
required this.data,
});
factory GetMunicipalitiesByProvinceResponseModel.fromJson(
Map<String, dynamic> json) =>
_$GetMunicipalitiesByProvinceResponseModelFromJson(json);
@override
Map<String, dynamic> toJson() =>
_$GetMunicipalitiesByProvinceResponseModelToJson(this);
}

municipality_model.dart

import 'package:delivery/app/data/models/andariego/andariego_models/base_andariego_model.dart';
import 'package:json_annotation/json_annotation.dart';
part 'municipality_model.g.dart';
@JsonSerializable()
class MunicipalityModel extends BaseAndariegoModel {
final int parent;
MunicipalityModel({
required super.id,
required super.name,
required this.parent,
});
factory MunicipalityModel.fromJson(Map<String, dynamic> json) =>
_$MunicipalityModelFromJson(json);
@override
Map<String, dynamic> toJson() => _$MunicipalityModelToJson(this);
}

api_response.json

{
"page": 1,
"page_size": 20,
"total": 11,
"pages": 1,
"prev_page": null,
"next_page": null,
"data": [
{
"id": 1188,
"name": "Consolación del Sur",
"parent": 58
},
{
"id": 1132,
"name": "Guane",
"parent": 58
},
{
"id": 1125,
"name": "La Palma",
"parent": 58
},
{
"id": 1124,
"name": "Los Palacios",
"parent": 58
},
{
"id": 1186,
"name": "Mantua",
"parent": 58
},
{
"id": 1182,
"name": "Minas de Matahambre",
"parent": 58
},
{
"id": 1189,
"name": "Pinar del Rio",
"parent": 58
},
{
"id": 1165,
"name": "Sandino",
"parent": 58
},
{
"id": 1133,
"name": "San Juan y Martínez",
"parent": 58
},
{
"id": 1187,
"name": "San Luis",
"parent": 58
},
{
"id": 1169,
"name": "Viñales",
"parent": 58
}
]
}

生成的代码

// GENERATED CODE - DO NOT MODIFY BY HAND
part of 'base_response_model.dart';
// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************
BaseResponseModel _$BaseResponseModelFromJson(Map<String, dynamic> json) =>
BaseResponseModel(
page: json['page'] as int,
pageSize: json['page_size'] as int,
total: json['total'] as int,
pages: json['pages'] as int,
prevPage: json['prev_page'] ?? 0,
nextPage: json['next_page'] ?? 0,
);
Map<String, dynamic> _$BaseResponseModelToJson(BaseResponseModel instance) =>
<String, dynamic>{
'page': instance.page,
'page_size': instance.pageSize,
'total': instance.total,
'pages': instance.pages,
'prev_page': instance.prevPage,
'next_page': instance.nextPage,
};

// GENERATED CODE - DO NOT MODIFY BY HAND
part of 'get_municipalities_by_province_response_model.dart';
// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************
GetMunicipalitiesByProvinceResponseModel
_$GetMunicipalitiesByProvinceResponseModelFromJson(
Map<String, dynamic> json) =>
GetMunicipalitiesByProvinceResponseModel(
page: json['page'] as int,
pageSize: json['page_size'] as int,
total: json['total'] as int,
pages: json['pages'] as int,
prevPage: json['prev_page'] ?? 0,
nextPage: json['next_page'] ?? 0,
data: (json['data'] as List<dynamic>)
.map((e) => MunicipalityModel.fromJson(e as Map<String, dynamic>))
.toList(),
);
Map<String, dynamic> _$GetMunicipalitiesByProvinceResponseModelToJson(
GetMunicipalitiesByProvinceResponseModel instance) =>
<String, dynamic>{
'page': instance.page,
'page_size': instance.pageSize,
'total': instance.total,
'pages': instance.pages,
'prev_page': instance.prevPage,
'next_page': instance.nextPage,
'data': instance.data,
};

// GENERATED CODE - DO NOT MODIFY BY HAND
part of 'municipality_model.dart';
// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************
MunicipalityModel _$MunicipalityModelFromJson(Map<String, dynamic> json) =>
MunicipalityModel(
id: json['id'] as int,
name: json['name'] as String,
parent: json['parent'] as int,
);
Map<String, dynamic> _$MunicipalityModelToJson(MunicipalityModel instance) =>
<String, dynamic>{
'id': instance.id,
'name': instance.name,
'parent': instance.parent,
};

我使用的是flutter, null safety

Answer 1

看起来JSON中缺少一个字段(或null)导致该问题。行号应该指向正确的位置!