需要一个“List<dynamic>”类型的值，但得到一个“_JsonMap”类型的值

Posted 2023-02-23

【中文标题】需要一个“List<dynamic>”类型的值，但得到一个“_JsonMap”类型的值

【英文标题】：Expected a value of type 'List<dynamic>', but got one of type '_JsonMap'

【发布时间】：2021-07-13 17:45:24

【问题描述】：

当我尝试 json 解码时，我收到错误 Expected a value of type 'List', but got one of type '_JsonMap'

我的代码：

  static Future<Response<Localizacao>> getLocalizacao(String cep) async 
    await Future.delayed(Duration(milliseconds: 200));
    try 
      Map<String, String> headers = 
        'Authorization': 'Token token=9e034db1f315356f30';
      String protocol = 'https://cors-anywhere.herokuapp.com/';
      String uri =
          'https://www.cepaberto.com/api/v3/cep?cep=' + cep;
      final endpoint = "&format=json";
      String url = protocol + uri + endpoint;

      final response = await http.get(url, headers: headers);

      if (response.statusCode == 200) 

        final json = response.body;

        List list = (jsonDecode(json) as List<dynamic>) ;

        final local = list.map<Localizacao>((map) => Localizacao.fromJson(map)).toList();

        return Response(true, msg: "OK", result: local[0]);
       else 
        return Response(false, msg: "Erro ao conectar no web service");
      
     catch (e) 

      return Response(false, msg: "Erro ao conectar no web service");
    
  

我尝试了其他方法，例如：

List list = convert.json.decode(response.body);
List list = convert.json.decode(json);

【参考方案1】：

找出问题所在。

我只需要添加：

final json = "[" + response.body + "]";

【参考方案2】：

试试这个

 if (response.statusCode == 200) 
        print("IF responde==200");
        final json = response.body;
        print("IF rjson");
        Map<String, dynamic> map= jsonDecode(json) ; 
        print("IF converting json");
        final local = Localizacao.fromJson(map);
        print("IF mapping list");
        return Response(true, msg: "OK", result: local);
       else 
        return Response(false, msg: "Erro ao conectar no web service");
      
     catch (e) 
      print("error in getLocalizacao: $e");
      return Response(false, msg: "Erro ao conectar no web service");
    

【讨论】：

"altitude":934.0,"cep":"82320520","latitude":"-25.3578899846","longitude":"-49.1953695819","logradouro":"Rua Ângela Budel" ,"bairro":"Butiatuvinha","cidade":"ddd":41,"ibge":"4106902","nome":"Curitiba","estado":"sigla":"PR"这是响应的返回，正文。我需要得到'纬度'和'经度'，当我按照你说的做时，我得到：期望一个'List'类型的值，但得到一个'String'类型的值

是的，因为 response.data['latitude'] 是字符串。另外，你为什么期待 List.您已经在字符串中拥有纬度、经度值