Flutter JSON Array Parsing getting error : Exception: type '(dynamic) => xxx is not a subtype of type '(Map<String, dynamic>) => List<xxx>' of 'f'

Question

抱歉，如果它重复了这个问题，但我没有找到解决方案。

错误：

Exception: type '(dynamic) => PostalModel' is not a subtype of type '(Map<String, dynamic>) => List' of 'f'

我做了什么：

正在调用 API:

Future<PostalModel> fetchPhotos(http.Client client) async {
   final response =
    await client.get('https://api.postalpincode.in/pincode/364710');

   // Use the compute function to run parsePhotos in a separate isolate.
   return compute(parsePostalPincode, response.body);
}

正在解析JSON:

 // A function that converts a response body into a List.
 PostalModel parsePostalPincode(String responseBody) {
   print(responseBody);
   final parsed = jsonDecode(responseBody).cast<Map<String, dynamic>>();
   print('Parsed : $parsed'); //Getting Log OUTPUT
   PostalModel postalModel = parsed.map<List<PostalModel>>((json) => PostalModel.fromJson(json));
   print('Postal Model : $postalModel'); //Getting Log OUTPUT
   return postalModel;
 }

正文中的绑定数据：

body: FutureBuilder<PostalModel>(
  future: fetchPhotos(http.Client()),
  builder: (context, snapshot) {
    print('snapshot $snapshot'); // Getting Error Here
    // "AsyncSnapshot<PostalModel>(ConnectionState.done, null, Exception: type '(dynamic) => PostalModel' is not a subtype of type '(Map<String, dynamic>) => List<PostalModel>' of 'f')"
    if (snapshot.hasError) print(snapshot.error);

    return snapshot.hasData
       ? PostOfficeList(postOfficeList: snapshot.data.postOffice)
       : Center(child: CircularProgressIndicator());
  },
),

您可以从 API Link 检查 JSON 我已经从 here.

创建了一个模型 class

Answer 1

API returns JSON 数组，而不是 JSON 对象，所以是 List，而不是 Map。

即如果您的模型 class 名称是 User，则 User JSON 是 JSON 数组的第一个元素。

因此要获取第一个元素，请使用第一个索引。内部获取信息更新

return Users.fromJson(jsonresponse[0]);

Answer 2

最后，我通过以下解决方案获得了成功：

// A function that converts a response body into a List.
PostalModel parsePostalPincode(String responseBody) {
  final parsed = jsonDecode(responseBody).cast<Map<String, dynamic>>();
  print('Parsed : $parsed[0]'); 
  PostalModel postalModel = PostalModel.fromJson(parsed[0]);
  print('Postal Model : $postalModel');
  return postalModel;
}

Flutter 对新手来说太疯狂了。 :P

Flutter JSON Array Parsing getting error : Exception: type '(dynamic) => xxx is not a subtype of type '(Map<String, dynamic>) => List<xxx>' of 'f'

Flutter JSON Array Parsing getting error : Exception: type '(dynamic) => xxx is not a subtype of type '(Map<String, dynamic>) => List<xxx>' of 'f'

arrays

json

flutter

jsonparser