Question

我每次调用api时，我的代码都会以某种方式返回此错误。

[ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type 'String' is not a subtype of type 'int'

昨天还好。我的Api电话总会发出。现在，每当我调用api时，该消息始终会发出。这是我的代码

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  bool _isLoading = false;
  List <Data> data = [];
  var countryController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Center(child: Text('CoronaVirus Tracker')),
        ),

        body: Column(
          children: <Widget>[
            Row(
              children: <Widget>[
                Expanded(
                  child: TextField(
                    decoration: InputDecoration(
                        border: InputBorder.none, hintText: 'Enter a Country'),
                    controller: countryController,
                  ),
                ),

                IconButton(
                    icon: Icon(Icons.search),
                    color: Colors.blue,
                    onPressed: () {
                      fetchData(countryController.text).then((newData) {
                        setState(() {
                          data = newData;
                          _isLoading = false;
                        });
                      });
                    }),
              ],
            ),

            _isLoading ? CircularProgressIndicator()
            :
            Expanded(
              child: ListView.builder(
                itemBuilder: (BuildContext context, int index) {
                  return Card(
                    child: ListTile(
                      title: Text(data[index].date.toString()),
                      subtitle: Text(data[index].cases.toString()),
                      onTap: () => {
                        Navigator.push(
                            context,
                            MaterialPageRoute(
                                builder: (context) =>
                                 Information()))
                      },
                    ),
                  );
                },
                itemCount: data.length,
              ),
            ),
          ],
        ));
  }
}

这是未来。

//The Api call
      Future <List<Data>> fetchData(String countryName) async {
        setState(() {
          _isLoading = true;
        });

    final response = await http.get('https://api.covid19api.com/live/country/malaysia/status/confirmed');
    if (response.statusCode == 200) {
      print(response.body);
      // Transform json into object
      json.decode(response.body).forEach((item){
        data.add(Data.fromJson(item));
      });
      return data;

    } else {
      // If the server did not return a 200 OK response,
      // then throw an exception.
      throw Exception('Failed to load data');
    }
  }

类构造器

class Data {
  final int date;
  final String country;
  final int cases;

  Data({this.date, this.country, this.cases});

  factory Data.fromJson(Map<String, dynamic> json) {
    return Data(
        country: json['Country'],
        date: json['Date'],
        cases: json['Confirmed']);
  }
}

我尝试了很多事情，但到目前为止，仍然没有任何效果。可以帮我吗？

Answer 1

问题是由数据模型中的日期字段引起的，从API返回的值是String，数据模型中描述的类型是int，从而导致类型转换问题，请按以下方式更新数据模型：

priceData1 == priceData2

Answer 2

我认为API的响应存在一些问题。因此，一旦尝试更改您的类构造函数代码，如下所示。希望对您有帮助。

 class Data {
  final String date;
  final String country;
  final int cases;

  Data({this.date, this.country, this.cases});

  factory Data.fromJson(Map<String, dynamic> json) {
 return Data(
    country: json['Country'],
    date: json['Date'],
    cases: json['Confirmed']);
 }
}

Answer 3

我不知道您使用的api是否更改了格式，但现在日期的类型为字符串

[
  {
    "Country": "Malaysia",
    "CountryCode": "MY",
    "Province": "",
    "City": "",
    "CityCode": "",
    "Lat": "4.21",
    "Lon": "101.98",
    "Confirmed": 4683,
    "Deaths": 76,
    "Recovered": 2108,
    "Active": 2499,
    "Date": "2020-04-13T00:00:00Z" //Is a String now
  },
...

因此，您必须将模型参数更新为字符串

final String date;

我的代码返回[ERROR：flutter / lib / ui / ui_dart_state.cc（157）]未处理的异常：类型'String'不是类型'int'的子类型

3 个答案: