Question

我已经尝试使用retrofit的给定教程尝试在Flutter中进行翻新。

当我尝试实现JsonHelper数据以检索帖子时，我的代码正常工作。但这不适用于我的服务器数据。

这是我从服务器检索的数据

{
    "data": [
        {
            "id": 2,
            "title": "Officiis explicabo et sed modi minus.",
            "body": "Et nihil error est tenetur optio eum. Magni molestias esse corrupti cumque excepturi aut autem.\n\nQuas pariatur aut assumenda. Optio est ullam nihil. Deleniti culpa qui fugit aspernatur qui non dolor. Deleniti et vel quasi maiores libero aut.\n\nAut repellendus occaecati sit et quasi. Aut qui quia cupiditate et totam modi nam officia. Nulla molestiae iste error et sapiente est amet sequi.\n\nVelit non voluptatem voluptas quod dolorem. Eos nesciunt perferendis quo ut dignissimos aliquid ex. Maiores sed tempore et. Molestiae dolores sed rerum.",
            "created_at": 1576508819,
            "featured_image": null,
            "user": {
                "username": "mikayla22",
                "user_since": "2019-12-16"
            },
            "categories": [
                "General",
                "Technology"
            ],
            "language": "English",
            "votes": 0
        },
    ]
}

我根据改造结果创建了podo，并在Flutter中实现了Class

Podo：

part 'post_api_service.g.dart';

@RestApi(baseUrl: "http://142")
abstract class RestClient {
  factory RestClient(Dio dio) = _RestClient;
  @GET("/posts")
  Future<Task<List<Post>>> getPosts();

}
@JsonSerializable()
class Post{
  int id;
  String title;
  String body;
  int created_at;
  String featured_image;
  User user;
  Categories categories;
  String language;
  int votes;
  Post({this.id, this.title, this.body, this.featured_image, this.categories, this.created_at, this.language, this.user, this.votes});

  factory Post.fromJson(Map<String, dynamic> json) => _$PostFromJson(json);
  Map<String, dynamic> toJson() => _$PostToJson(this);
}

class User{
  String username;
  String user_since;

  User({this.username, this.user_since});
  factory User.from(Map<String, dynamic> json) => _$UserFromJson(json);
  Map<String, dynamic> toJson() => _$UserToJson(this);
}

class Categories{
  List<String> categories;

  Categories({this.categories});

  factory Categories.from(Map<String, dynamic> json) => _$CategoriesFromJson(json);
  Map<String, dynamic> toJson() => _$CategoriesToJson(this);
}

class Task<T>{
  T data;

  Task({this.data});

  factory Task.fromJson(Map<String, dynamic> json) => _$TaskFromJson(json);
  Map<String, dynamic> toJson() => _$TaskToJson(this);
}

这是我的

Service.g.dart：

User _$UserFromJson(Map<String, dynamic> json){
  return User(
      username: json['username'] as String,
      user_since: json['user_since'] as String
  );
}

Map<String, dynamic> _$UserToJson(User instance) => <String, dynamic>{
  'username' : instance.username,
  'user_since' : instance.user_since
};

Categories _$CategoriesFromJson(Map<String, dynamic> json){
  return Categories(
      categories: json['categories'] as List<String>
  );
}

Map<String, dynamic> _$CategoriesToJson(Categories instance) => <String, dynamic>{
  'categories' : instance.categories
};

Task _$TaskFromJson(Map<String, dynamic> json){
  return Task(
      data: json['data']
  );
}

Map<String, dynamic> _$TaskToJson(Task instance) => <String, dynamic>{
  'data' : instance.data
};


Post _$PostFromJson(Map<String, dynamic> json){
  return Post(
      id: json['id'] as int,
      user: json['user'] as User,
      categories: json['categories'] as Categories,
      body: json['body'] as String,
      created_at: json['created_at'] as int,
      featured_image: json['featured_image'] as String,
      language: json['language'] as String,
      votes: json['votes'] as int,
      title: json['title'] as String
  );
}

Map<String, dynamic> _$PostToJson(Post instance) => <String, dynamic>{
  'id' : instance.id,
  'user' : instance.user,
  'categories' : instance.categories,
  'body' : instance.body,
  'created_at' : instance.created_at,
  'featured_image' : instance.featured_image,
  'language' : instance.language,
  'votes': instance.votes,
  'title': instance.title
};

class _RestClient implements RestClient {
  _RestClient(this._dio, {this.baseUrl}) {
    ArgumentError.checkNotNull(_dio, '_dio');
    this.baseUrl ??= 'http://142';
  }

  final Dio _dio;

  String baseUrl;

  @override
  getPosts() async {
    const _extra = <String, dynamic>{};
    final queryParameters = <String, dynamic>{};
    final _data = <String, dynamic>{};
    final Response<Map<String, dynamic>> _result = await _dio.request('/posts',
        queryParameters: queryParameters,
        options: RequestOptions(
            method: 'GET',
            headers: <String, dynamic>{},
            extra: _extra,
            baseUrl: baseUrl),
        data: _data);
    final value = Task<List<Post>>.fromJson(_result.data);
    return Future.value(value);
  }
}

但是当我尝试获取数据时

builder: (context, snapshot) {
    if (snapshot.connectionState == ConnectionState.done) {
        print(snapshot.data);
        List<Post> posts = snapshot.data.data;
        return _buildPosts(context, posts);
    } else {
        return Center(
            child: CircularProgressIndicator(),
        );
    }
},

如果您有任何问题，请问我，我将通过代码进行解释。但是请与输出混淆。

Answer 1

我认为这是问题所在

    final value = Task<List<Post>>.fromJson(_result.data);

您需要从JSON逐元素解析元素才能发布。可以使用地图完成以下操作：

    final value = List<Post>.from(_result.data.map((i) => Post.fromJson(i)));

数据显示为空但url在Postman上有效

1 个答案: