I'm trying to make a request to an external API, but when the response goes through JsonDecode, and it maps the created array variable, it returns this error

I'm new to flutter, and I'm getting a weather forecast API, where you can see the code below

    List<Data> lsPrevisaoTempo = [];

  _getPrediction() async {
    SharedPreferences pref = await SharedPreferences.getInstance();

    var countyID = pref.getInt("county_id") ?? "";

    API.getPredictionTime().then((response) {
      setState(() {
        if (response.statusCode == 200) {
          var jsonResponse = jsonDecode(response.body) as Map<String, dynamic>;
          weatherForecastList = jsonResponse["${countyID}"].map<Data>((json) => Data.fromJson(json)).toList();
        }
      });
    });

Below, the receipt of the request

static Future getPredictionTime() async {
    SharedPreferences pref = await SharedPreferences.getInstance();
    var countyId = pref.getInt("county_id") ?? "";

    Map<String, String> headers = {'Content-Type': 'application/json'};

    var url =
        Uri.parse("https://apiprevmet3.inmet.gov.br/previsao/${countyId}");

    return await http.get(url, headers: headers);
  }

The Date Model below:

class Data {
  Periodo? manha;
  Periodo? tarde;
  Periodo? noite;

  Data({this.manha, this.tarde, this.noite});

  Data.fromJson(Map<String, dynamic> json) {
    manha = json['manha'] != null ? new Periodo.fromJson(json['manha']) : null;
    tarde = json['tarde'] != null ? new Periodo.fromJson(json['tarde']) : null;
    noite = json['noite'] != null ? new Periodo.fromJson(json['noite']) : null;
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.manha != null) {
      data['manha'] = this.manha!.toJson();
    }
    if (this.tarde != null) {
      data['tarde'] = this.tarde!.toJson();
    }
    if (this.noite != null) {
      data['noite'] = this.noite!.toJson();
    }
    return data;
  }
}

class Periodo {
  String? uf;
  String? entidade;
  String? resumo;
  String? tempo;
  int? tempMax;
  int? tempMin;
  String? dirVento;
  String? intVento;
  String? codIcone;
  String? icone;
  String? diaSemana;
  int? umidadeMax;
  int? umidadeMin;
  String? tempMaxTende;
  String? codTempMaxTendeIcone;
  String? tempMaxTendeIcone;
  String? tempMinTende;
  String? codTempMinTendeIcone;
  String? tempMinTendeIcone;
  String? estacao;
  String? hora;
  String? nascer;
  String? ocaso;
  String? fonte;

  Periodo(
      {this.uf,
      this.entidade,
      this.resumo,
      this.tempo,
      this.tempMax,
      this.tempMin,
      this.dirVento,
      this.intVento,
      this.codIcone,
      this.icone,
      this.diaSemana,
      this.umidadeMax,
      this.umidadeMin,
      this.tempMaxTende,
      this.codTempMaxTendeIcone,
      this.tempMaxTendeIcone,
      this.tempMinTende,
      this.codTempMinTendeIcone,
      this.tempMinTendeIcone,
      this.estacao,
      this.hora,
      this.nascer,
      this.ocaso,
      this.fonte});

  Periodo.fromJson(Map<String, dynamic> json) {
    uf = json['uf'] ?? "";
    entidade = json['entidade'] ?? "";
    resumo = json['resumo'] ?? "";
    tempo = json['tempo'] ?? "";
    tempMax = json['temp_max'] ?? 0;
    tempMin = json['temp_min'] ?? 0;
    dirVento = json['dir_vento'] ?? "";
    intVento = json['int_vento'] ?? "";
    codIcone = json['cod_icone'] ?? "";
    icone = json['icone'] ?? "";
    diaSemana = json['dia_semana'] ?? "";
    umidadeMax = json['umidade_max'] ?? 0;
    umidadeMin = json['umidade_min'] ?? 0;
    tempMaxTende = json['temp_max_tende'] ?? "";
    codTempMaxTendeIcone = json['cod_temp_max_tende_icone'] ?? "";
    tempMaxTendeIcone = json['temp_max_tende_icone'] ?? "";
    tempMinTende = json['temp_min_tende'] ?? "";
    codTempMinTendeIcone = json['cod_temp_min_tende_icone'] ?? "";
    tempMinTendeIcone = json['temp_min_tende_icone'] ?? "";
    estacao = json['estacao'] ?? "";
    hora = json['hora'] ?? "";
    nascer = json['nascer'] ?? "";
    ocaso = json['ocaso'] ?? "";
    fonte = json['fonte'] ?? "";
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['uf'] = this.uf;
    data['entidade'] = this.entidade;
    data['resumo'] = this.resumo;
    data['tempo'] = this.tempo;
    data['temp_max'] = this.tempMax;
    data['temp_min'] = this.tempMin;
    data['dir_vento'] = this.dirVento;
    data['int_vento'] = this.intVento;
    data['cod_icone'] = this.codIcone;
    data['icone'] = this.icone;
    data['dia_semana'] = this.diaSemana;
    data['umidade_max'] = this.umidadeMax;
    data['umidade_min'] = this.umidadeMin;
    data['temp_max_tende'] = this.tempMaxTende;
    data['cod_temp_max_tende_icone'] = this.codTempMaxTendeIcone;
    data['temp_max_tende_icone'] = this.tempMaxTendeIcone;
    data['temp_min_tende'] = this.tempMinTende;
    data['cod_temp_min_tende_icone'] = this.codTempMinTendeIcone;
    data['temp_min_tende_icone'] = this.tempMinTendeIcone;
    data['estacao'] = this.estacao;
    data['hora'] = this.hora;
    data['nascer'] = this.nascer;
    data['ocaso'] = this.ocaso;
    data['fonte'] = this.fonte;
    return data;
  }
}

CodePudding user response：

As I see, that you're trying to call a List specific method which is map() on a Map<String, dynamic>, you can't execute a List type method on Map<String, dynamic>.

On other hand, you call values on the Map<String, dynamic> to get a List with just the values.

so, you need to replace this:

weatherForecastList = jsonResponse["${countyID}"].map<Data>((json) => Data.fromJson(json)).toList();

with:

 weatherForecastList = jsonResponse["${countyID}"].values.toList().map((mapElement) => Data.fromJson(mapElement as Map<String, dynamic>)).toList();

CodePudding user response：

Your jsonResponse["${countyID}"] contains a Map not List, if you want to map it you need to use entries, change this:

weatherForecastList = jsonResponse["${countyID}"].map<Data>((json) => Data.fromJson(json)).toList();

to this:

weatherForecastList = jsonResponse["${countyID}"].entries.map<Data>((json) => Data.fromJson({json.key:json.value})).toList();