获取数据 flutter api

Question

我想从 API 获取数据，我尝试了 postman 中的链接，它在这里工作的是：[ {“Id”：“14”，“title”：“Facebook vs instagram？”，}，{“Id”：“ 15", "title": "Facebook vs instagram?", }, { "Id": "16", "title": "Facebook vs instagram?", }, ]

但是当我尝试执行 map 时，会出现此错误：error catch type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'List' in type cast。

这是我的代码：此文件中出现此错误并打印（收到）打印与 postman 相同的数据，但 map httpservice.dart 中的问题：`

class HttpService {
  final String postsURL =
      "";

  Future<List<Post>> getPosts() async {
    var request = http.MultipartRequest("POST", Uri.parse(postsURL));

    request.fields.addAll(
      {
        'post_type': "read_user",
        'uid': "27",
      },
    );

    var headers = {
      'token': "aaa",
      'lang': "lang",
    };

    request.headers.addAll(headers);
    List<Post> Posts = [];
    try {
      http.StreamedResponse response = await request.send();

      if (response.statusCode == 200) {
        var response = await http.Response.fromStream(streamedResponse);
final result = jsonDecode(response.body) as List; 

        List<Post> posts = result
            .map(
              (dynamic item) => Post.fromJson(item),
            )
            .toList();

        return Posts;
      } else {
        print("error response $response.statusCode");
      }
    } catch (e) {
      print("error catch $e");
    }
    return Posts;
  }
}

` post_model.dart：

`

class后{

  final String Id;
  final String title;

  Post({
    required this.Id,
    required this.title,
  });

  factory Post.fromJson(Map<String, dynamic> json) {
    return Post(
       Id: json['Id'] as String,
      title: json['title'] as String,
    );
  }
}

` post.dart：

class PostsPage extends StatelessWidget {
  final HttpService httpService = HttpService();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Posts"),
      ),
      body: FutureBuilder(
        future: httpService.getPosts(),
        builder: (BuildContext context, AsyncSnapshot<List<Post>> snapshot) {
          if (snapshot.hasData) {
            List<Post> posts = snapshot.data!;
            return ListView(
              children: posts
                  .map(
                    (Post post) => ListTile(
                      title: Text(post.title),
                      subtitle: Text("${post.Id}"),
                    ),
                  )
                  .toList(),
            );
          } else {
            return Center(child: CircularProgressIndicator());
          }
        },
      ),
    );
  }
}

Answer 1

http package 默认数据为 json。 您再次尝试对响应正文进行解码，但 jsonDecode 需要字符串类型作为参数。

简单地说，您需要做的就是删除 jsonDecode

从

final result = jsonDecode(response.body) as List; 

至

final result = response.body as Map<String, dynamic>;