json - Flutter:从json列表中获取数据

Question

我正在通过 URL JSON 做一个与气候相关的学习项目，我得到你的数据并在应用程序中显示它们

我正在尝试从 JSON 中获取数据。当我尝试获取数据时收到错误消息:类型“_TypeError”不是类型“Widget”的子类型我想解决这个问题，感谢任何最小的帮助，谢谢。

我的 JSON:

{
  "metcheckData": {
    "forecastLocation": {
      "forecast": [
        {
          "temperature": "18",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4656",
          "uvIndex": "0",
          "totalcloud": "8",
          "lowcloud": "8",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "84",
          "windspeed": "9",
          "meansealevelpressure": "1018.02",
          "windgustspeed": "11",
          "winddirection": "28.7724",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "3",
          "weekday": "Tuesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-19T23:00:00.00"
        },
        {
          "temperature": "18",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4663",
          "uvIndex": "0",
          "totalcloud": "8",
          "lowcloud": "8",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "85",
          "windspeed": "9",
          "meansealevelpressure": "1018.26",
          "windgustspeed": "11",
          "winddirection": "29.4946",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T00:00:00.00"
        },
        {
          "temperature": "18",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4666",
          "uvIndex": "0",
          "totalcloud": "8",
          "lowcloud": "8",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "86",
          "windspeed": "9",
          "meansealevelpressure": "1018.18",
          "windgustspeed": "10",
          "winddirection": "30.0925",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T01:00:00.00"
        },
        {
          "temperature": "18",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4668",
          "uvIndex": "0",
          "totalcloud": "11",
          "lowcloud": "11",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "87",
          "windspeed": "8",
          "meansealevelpressure": "1017.79",
          "windgustspeed": "10",
          "winddirection": "30.761",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T02:00:00.00"
        },
        {
          "temperature": "17",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4671",
          "uvIndex": "0",
          "totalcloud": "12",
          "lowcloud": "12",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "87",
          "windspeed": "8",
          "meansealevelpressure": "1017.36",
          "windgustspeed": "9",
          "winddirection": "31.0844",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T03:00:00.00"
        },
        {
          "temperature": "17",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4673",
          "uvIndex": "0",
          "totalcloud": "11",
          "lowcloud": "11",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "88",
          "windspeed": "8",
          "meansealevelpressure": "1017.04",
          "windgustspeed": "9",
          "winddirection": "31.4161",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T04:00:00.00"
        },
        {
          "temperature": "17",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4671",
          "uvIndex": "0",
          "totalcloud": "11",
          "lowcloud": "11",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "89",
          "windspeed": "7",
          "meansealevelpressure": "1016.89",
          "windgustspeed": "9",
          "winddirection": "31.2326",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T05:00:00.00"
        },
        {
          "temperature": "17",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4668",
          "uvIndex": "0",
          "totalcloud": "10",
          "lowcloud": "10",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "91",
          "windspeed": "8",
          "meansealevelpressure": "1017.04",
          "windgustspeed": "9",
          "winddirection": "30.2947",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T06:00:00.00"
        },
        {
          "temperature": "17",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4664",
          "uvIndex": "0",
          "totalcloud": "9",
          "lowcloud": "9",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "92",
          "windspeed": "8",
          "meansealevelpressure": "1017.35",
          "windgustspeed": "10",
          "winddirection": "29.0404",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T07:00:00.00"
        },
        {
          "temperature": "17",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4664",
          "uvIndex": "0",
          "totalcloud": "16",
          "lowcloud": "16",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "91",
          "windspeed": "9",
          "meansealevelpressure": "1017.77",
          "windgustspeed": "10",
          "winddirection": "27.9231",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T08:00:00.00"
        },
        {
          "temperature": "18",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4673",
          "uvIndex": "1",
          "totalcloud": "32",
          "lowcloud": "32",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "86",
          "windspeed": "9",
          "meansealevelpressure": "1018.05",
          "windgustspeed": "11",
          "winddirection": "25.3295",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T09:00:00.00"
        },
        {
          "temperature": "18",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4687",
          "uvIndex": "2",
          "totalcloud": "38",
          "lowcloud": "38",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "82",
          "windspeed": "9",
          "meansealevelpressure": "1018.31",
          "windgustspeed": "10",
          "winddirection": "22.0118",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T10:00:00.00"
        },
        {
          "temperature": "19",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4702",
          "uvIndex": "3",
          "totalcloud": "36",
          "lowcloud": "36",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "76",
          "windspeed": "9",
          "meansealevelpressure": "1018.56",
          "windgustspeed": "10",
          "winddirection": "18.4385",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T11:00:00.00"
        },
        {
          "temperature": "20",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4712",
          "uvIndex": "4",
          "totalcloud": "31",
          "lowcloud": "31",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "72",
          "windspeed": "9",
          "meansealevelpressure": "1018.79",
          "windgustspeed": "9",
          "winddirection": "14.9684",
          "windletter": "NNE",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T12:00:00.00"
        },
        {
          "temperature": "20",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4722",
          "uvIndex": "5",
          "totalcloud": "26",
          "lowcloud": "26",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "69",
          "windspeed": "9",
          "meansealevelpressure": "1018.9",
          "windgustspeed": "8",
          "winddirection": "12.5729",
          "windletter": "W",
          "icon": "FA",
          "iconName": "Fair",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T13:00:00.00"
        },
        {
          "temperature": "21",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4739",
          "uvIndex": "10",
          "totalcloud": "1",
          "lowcloud": "1",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "68",
          "windspeed": "9",
          "meansealevelpressure": "1018.83",
          "windgustspeed": "8",
          "winddirection": "10.6461",
          "windletter": "N",
          "icon": "SU",
          "iconName": "Sunny",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T14:00:00.00"
        },
        {
          "temperature": "21",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4765",
          "uvIndex": "10",
          "totalcloud": "1",
          "lowcloud": "1",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "67",
          "windspeed": "9",
          "meansealevelpressure": "1018.59",
          "windgustspeed": "8",
          "winddirection": "9.82178",
          "windletter": "N",
          "icon": "SU",
          "iconName": "Sunny",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T15:00:00.00"
        },
        {
          "temperature": "21",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4797",
          "uvIndex": "10",
          "totalcloud": "1",
          "lowcloud": "1",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "67",
          "windspeed": "9",
          "meansealevelpressure": "1018.34",
          "windgustspeed": "8",
          "winddirection": "9.66212",
          "windletter": "N",
          "icon": "SU",
          "iconName": "Sunny",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T16:00:00.00"
        },
        {
          "temperature": "21",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4826",
          "uvIndex": "9",
          "totalcloud": "1",
          "lowcloud": "1",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "68",
          "windspeed": "9",
          "meansealevelpressure": "1017.98",
          "windgustspeed": "8",
          "winddirection": "8.49407",
          "windletter": "N",
          "icon": "SU",
          "iconName": "Sunny",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T17:00:00.00"
        },
        {
          "temperature": "20",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4844",
          "uvIndex": "9",
          "totalcloud": "1",
          "lowcloud": "1",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "70",
          "windspeed": "9",
          "meansealevelpressure": "1017.81",
          "windgustspeed": "9",
          "winddirection": "8.70691",
          "windletter": "N",
          "icon": "SU",
          "iconName": "Sunny",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "D",
          "utcTime": "2018-06-20T18:00:00.00"
        },
        {
          "temperature": "20",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4857",
          "uvIndex": "8",
          "totalcloud": "1",
          "lowcloud": "1",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "72",
          "windspeed": "10",
          "meansealevelpressure": "1017.93",
          "windgustspeed": "10",
          "winddirection": "10.5324",
          "windletter": "N",
          "icon": "SU",
          "iconName": "Sunny",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T19:00:00.00"
        },
        {
          "temperature": "19",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4872",
          "uvIndex": "2",
          "totalcloud": "1",
          "lowcloud": "1",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "74",
          "windspeed": "10",
          "meansealevelpressure": "1018.25",
          "windgustspeed": "11",
          "winddirection": "13.7294",
          "windletter": "NNE",
          "icon": "SU",
          "iconName": "Sunny",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T20:00:00.00"
        },
        {
          "temperature": "19",
          "dewpoint": "15",
          "rain": "0",
          "freezinglevel": "4889",
          "uvIndex": "1",
          "totalcloud": "1",
          "lowcloud": "1",
          "medcloud": "0",
          "highcloud": "0",
          "humidity": "78",
          "windspeed": "11",
          "meansealevelpressure": "1018.64",
          "windgustspeed": "13",
          "winddirection": "17.2073",
          "windletter": "NNE",
          "icon": "SU",
          "iconName": "Sunny",
          "chanceofrain": "0",
          "chanceofsnow": "0",
          "dayOfWeek": "4",
          "weekday": "Wednesday",
          "sunrise": "6:57",
          "sunset": "19:04",
          "dayOrNight": "N",
          "utcTime": "2018-06-20T21:00:00.00"
        },
      ],
      "continent": "",
      "country": "",
      "location": "28.0/-15.6",
      "latitude": 28.0,
      "longitude": -15.6,
      "timezone": 1
    }
  },
  "feedCreation": "2018-06-19T23:05:19.00",
  "feedCreator": "Metcheck.com",
  "feedModel": "GHX2",
  "feedModelRun": "12Z",
  "feedModelRunInitialTime": "2018-06-19T12:00:00.00",
  "feedResolution": "0.01"
}

我的 Dart 代码

 @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: new AppBar(
        title: new Text("G.C. - WEATHER"),
        centerTitle: true,
        backgroundColor: Colors.blue[700],
      ),
      body: new Container(
        child: new RefreshIndicator(
          onRefresh: _autoRefresh,
            child: new ListView(
              children: <Widget>[
                new FutureBuilder<List<Post>>(
                  future: fetchPosts(),
                  builder: (context, snapshot) {
                    if (snapshot.hasData){
                      List<Post> posts = snapshot.data;
                      return new Column(
                          children: posts.map((post) => new Column(
                            children: <Widget>[
                              new Text(post.temperature),
                            ],
                          )).toList()
                      );
                    }
                    else if(snapshot.hasError)
                    {
                      return snapshot.error;
                    }
                    return new Center(
                      child: new Column(
                        children: <Widget>[
                          new Padding(padding: new EdgeInsets.all(50.0)),
                          new CircularProgressIndicator(),
                        ],
                      ),
                    );
                  },
                ),
                
              ],
            ),
        ),
      ),
    );
  }
}

在我的 DART 代码中获取数据发布

Future<List<Post>> fetchPosts() async {
  http.Response response = await http.get('http://ws1.metcheck.com/ENGINE/v9_0/json.asp?lat=28&lon=-15.6&lid=62228&Fc=No');
  List responseJson = json.decode(response.body);
  return responseJson.map((m) => new Post.fromJson(m)).toList();
}

class Post {
  final String temperature, rain, humidity, sunrise, sunset, updateDate;

  Post({
    this.temperature,
    this.rain,
    this.humidity,
    this.sunrise,
    this.sunset,
    this.updateDate,
  });

  factory Post.fromJson(Map<String, dynamic> json) {
    return new Post(
      temperature: json['metcheckData']['forecastLocation']['forecast']['temperature'].toString(),
      rain: json['metcheckData']['forecastLocation']['forecast']['rain'].toString(),
      humidity:json['metcheckData']['forecastLocation']['forecast']['humidity'].toString(),
      sunrise: json['metcheckData']['forecastLocation']['forecast']['sunrise'].toString(),
      sunset: json['metcheckData']['forecastLocation']['forecast']['sunset'].toString(),
      updateDate: json['metcheckData']['forecastLocation']['forecast']['utcTime'].toString(),
    );
  }
}

Answer 1

查看您的 json 和代码后，我发现您的 json 的根不是 JsonArray，而是 JsonObject。您尝试获取的列表在 ['metcheckData']['forecastLocation']['forecast']

中

在这里，我对您的代码进行了更改，并且可以正常工作..

Future<List<Post>> fetchPosts() async {
  http.Response response = await http.get(
      'http://ws1.metcheck.com/ENGINE/v9_0/json.asp?lat=28&lon=-15.6&lid=62228&Fc=No');
  var responseJson = json.decode(response.body);
  return (responseJson['metcheckData']['forecastLocation']['forecast'] as List)
      .map((p) => Post.fromJson(p))
      .toList();
}

class Post {
  final String temperature, rain, humidity, sunrise, sunset, updateDate;

  Post({
    this.temperature,
    this.rain,
    this.humidity,
    this.sunrise,
    this.sunset,
    this.updateDate,
  });

  factory Post.fromJson(Map<String, dynamic> json) {
    return new Post(
      temperature: json['temperature'].toString(),
      rain: json['rain'].toString(),
      humidity: json['humidity'].toString(),
      sunrise: json['sunrise'].toString(),
      sunset: json['sunset'].toString(),
      updateDate: json['utcTime'].toString(),
    );
  }
}