当我使用json库处理返回值http.response时出现错误400

Question

我已成功尝试从我的 URL 检索数据。我正在尝试分离数据，以便我可以使用我不熟悉的 JSON 单独处理它......

当我更改代码时，我收到错误 400。我确信 URL 没有问题，因为它以前工作过

import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as http;

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: busNearby(),
    );
  }
}

class busNearby extends StatefulWidget {
  const busNearby({super.key});

  @override
  busNearbyState createState() => busNearbyState();
}

class busNearbyState extends State<busNearby> {
  final TextEditingController queryController = TextEditingController();
  List<Map<String, dynamic>> dataList = [];
  String busCode = '';
  late BuildContext scaffoldContext;

   String? busServiceNo;
   String? actualTime;
   String? relativeTime;


  Future<void> fetchData(String userInput) async{
    try{
      var response = await http.post(
        Uri.parse('https://laravelsyd-fypfinalver.herokuapp.com/getBusService'),

        headers: <String, String>{
          'Content-Type': 'application/json; charset=UTF-8',
        },
        body:
        json.encode({'bus_stop_id': busCode}),
      );
      hndleResponse(response);

    }catch (e){
      print("Error : $e");
    }
    print(busCode);
  }

  void hndleResponse(http.Response a) {
    if (a.statusCode >= 200 && a.statusCode < 300){
      List<dynamic> returnedData = json.decode(a.body);

      if(returnedData.isNotEmpty){
        busServiceNo = returnedData[0]['bus_service_no'];
        actualTime = returnedData[0]['eta']['time'][0];
        relativeTime = returnedData[0]['eta'][0]['relative_time'];
      }

      setState(() {});
    }else {
      print("Error:  ${a.statusCode}");
    }
    print(a.statusCode);
    print(busServiceNo);
    print(actualTime );
    print(relativeTime );

  }



  // Function to show fetched data or an error message in a bottom sheet
 void showFetchedData() {
    showModalBottomSheet(
      context: scaffoldContext,
      builder: (BuildContext context) {
        if (dataList.isEmpty) {
          return Container(
            padding: const EdgeInsets.all(16.0),
            child: const Text('No data available.'),
          );
        } else {
          return ListView.builder(
            itemCount: dataList.length,
            itemBuilder: (context, index) {
              final item = dataList[index];
              return SizedBox(
                height: 100,
                child: Card(
                  color: Colors.lightBlue[100],
                  child: Padding(
                    padding: const EdgeInsets.all(12.0),
                    child: Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text('Bus Code: ${item['bus_service_no']}'),
                        Text('Arrival Time: ${item['eta'].toString()}'),

                      ],
                    ),
                  ),
                ),
              );
            },
          );
        }
      },
    );
  }




  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Data Retrieval Example'),
      ),
      body: Center(
        child: Column(
          children: <Widget>[
            Padding(
              padding: const EdgeInsets.all(16.0),
              child: TextField(
                onChanged: (value){
                  setState(() {
                    busCode = value;
                  });
                },
                controller: queryController,
                decoration: const InputDecoration(
                  labelText: 'Enter Bus Service Code',

                ),
              ),
            ),
            Builder(
              builder: (context) {
                scaffoldContext = context;
                return ElevatedButton(
                  onPressed: () async {
                    await fetchData(queryController.text);
                    showFetchedData(); // Call this method after data is fetched
                  },
                  child: const Text('Fetch Data'),
                );
                
              },
            ),
            if (dataList.isNotEmpty) // Show fetched data if available
              Expanded(
                child: ListView.builder(
                  itemCount: dataList.length,
                  itemBuilder: (context, index) {
                    final item = dataList[index];
                    return SizedBox(
                      height: 10,
                      child: Card(
                        child: Padding(
                          padding: const EdgeInsets.all(8.0),
                          child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: [
                              Text('Bus Code: ${item['bus_service_no']}'),
                              Text('ETA (minutes): ${item['relative_time']}'),
                            ],
                          ),
                        ),
                      ),
                    );


                  },
                ),
              ),
            DataTable(
              columns: const <DataColumn>[
                DataColumn(label: Text('Service Code')),
                DataColumn(label: Text('Location')),
              ],
              rows: const <DataRow>[
                DataRow(cells: <DataCell>[
                  DataCell(Text('1076')),
                  DataCell(Text('Larkin Terminal')),
                ]),
                DataRow(cells: <DataCell>[
                  DataCell(Text('1084')),
                  DataCell(Text('Taman Universiti')),
                ]),
                DataRow(cells: <DataCell>[
                  DataCell(Text('1019')),
                  DataCell(Text('Skudai Prade')),
                ]),
                DataRow(cells: <DataCell>[
                  DataCell(Text('1052')),
                  DataCell(Text('Opposite Skudai Prade')),
                ]),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

输出：返回特定公交车站所有公交车服务的预计到达时间。绝对时间和相对时间，即26分钟和38分钟到达

[
    { 
        "route_id": 1,
        "bus_service_no": "7",
        "eta": [
                   { "time": "2020-07-10 15:17:07",
                     "relative_time": 26 },
                   { "time":"2020-07-10 15:29:21",
                     "relative_time":38 }
               ]
     }
]

我正在尝试使用json库来分别显示公交车服务号、时间和相对时间

Answer 1

当您获得 JSON 输出时，您的请求没有任何问题。如果它返回错误代码 400，这意味着问题出在您的服务器上，您必须检查是否手动返回了该状态。