如何从 Flutter 中的多行加载 json

Question

我正在尝试加载从 Web 服务获取的数据，但没有任何结果。 JSON 恢复正常，但我无法将其解码以在我的应用程序中使用。我还可以在 Web 浏览器中使用该 URL，并且 JSON 可以正常返回。我想我可能试图错误地解码和加载 JSON。 任何关于我哪里出错的帮助都会很棒。谢谢大家。

干杯，

保罗

JSON 示例：

{
   "rows":[
      {
         "JOBID":23,
         "START_DATE":1588809600000,
         "START_TIME":"07:30",
         "JOB_NAME":"Cleaner"
      },
      {
         "JOBID":23,
         "START_DATE":1588809600000,
         "START_TIME":"08:30",
         "JOB_NAME":"Manager"
      }
   ]
}

型号：

class StaffJobs {
  List<SJRows> sjRows;

  StaffJobs({this.sjRows});

  StaffJobs.fromJson(Map<String, dynamic> json) {
    if (json['rows'] != null) {
      sjRows = List<SJRows>();
      json['rows'].forEach((v) {
        sjRows.add(SJRows.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = Map<String, dynamic>();
    if (this.sjRows != null) {
      data['rows'] = this.sjRows.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class SJRows {
  int jobId;
  int startDate;
  String startTime;
  String jobName;

  SJRows(
      {this.jobId,
      this.startDate,
      this.startTime,
      this.jobName});

  SJRows.fromJson(Map<String, dynamic> json) {
    jobId = json['JOBID'];
    startDate = json['START_DATE'];
    startTime = json['START_TIME'];
    jobName = json['JOB_NAME'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = Map<String, dynamic>();
    data['JOBID'] = this.jobId;
    data['START_DATE'] = this.startDate;
    data['START_TIME'] = this.startTime;
    data['JOB_NAME'] = this.jobName;
    return data;
  }
}

在我打印作业计数的 initState 中，我得到 0。

在我在 ListTile 中显示几个字段的代码末尾附近，我不确定如何引用数据。

在我测试 response.statusCode 为 200 之后，我尝试将 response.body 打印到控制台并且所有 JSON 都在那里，所以 http.get 工作正常。

我还在控制台中看到一个错误： E/flutter (15432): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] 未处理的异常：类型“_InternalLinkedHashMap”不是类型转换中“List”类型的子类型

在我尝试加载员工职位的屏幕中，我有以下代码：

class MyJobs extends StatefulWidget {
  @override
  _MyJobsState createState() => new _MyJobsState();
}

class _MyJobsState extends State<MyJobs> {
  List<StaffJobs> jobs = List();
  bool isLoading = false;

  _getJobs() async {
    setState(() {
      isLoading = true;
    });
    final response = await http.get(Uri.encodeFull('$jobUrl'));
    if (response.statusCode == 200) {
      setState(() {
        isLoading = false;
      });
      jobs = (json.decode(response.body) as List).map((data) => StaffJobs.fromJson(data)).toList();
    } else {
      throw Exception('Failed to load jobs');
    }
  }

  @override
  void initState() {
    super.initState();
    _getJobs();
    print('Count = ${jobs.length}');
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: rmoAppBar(subText: 'My Jobs'),
      drawer: RmoMenu(),
      body: isLoading
          ? Center(child: CircularProgressIndicator())
          : Container(
              child: ListView.builder(
                itemCount: jobs.length,
                itemBuilder: (BuildContext context, int index) {
                  return ListTile(
                    title: Text(jobs[index].sjRows.jobName),    <------ Not sure how to reference data
                    subtitle: Text(jobs[index].sjRows.startTime),  <--- This doesn't compile
                  );
                },
              ),
            ),
    );
  }
}

Answer 1

你不是 正确解码。

跟随代码，同时帮助你更多。

class MyJobs extends StatefulWidget {
  @override
  _MyJobsState createState() => new _MyJobsState();
}

class _MyJobsState extends State<MyJobs> {
  StaffJobs jobs;
  bool isLoading = false;

  _getJobs() async {
    setState(() {
      isLoading = true;
    });
    final response = await http.get(Uri.encodeFull('$jobUrl'));
    if (response.statusCode == 200) {
      setState(() {
        isLoading = false;
      });
      jobs = StaffJobs.fromJson(json.decode(response.body));
    } else {
      throw Exception('Failed to load jobs');
    }

    setState(() {
      isLoading = false;
    });
  }

  @override
  void initState() {
    super.initState();
    _getJobs();
    print('Count = ${jobs.sjRows.length}');
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: rmoAppBar(subText: 'My Jobs'),
      drawer: RmoMenu(),
      body: isLoading
          ? Center(child: CircularProgressIndicator())
          : Container(
              child: ListView.builder(
                itemCount: jobs.sjRows.length,
                itemBuilder: (BuildContext context, int index) {
                  return ListTile(
                    title: Text(jobs.sjRows[index].jobName),
                    subtitle: Text(jobs.sjRows[index].startTime),
                  );
                },
              ),
            ),
    );
  }
}

class StaffJobs {
  List<SJRows> sjRows;

  StaffJobs({this.sjRows});

  StaffJobs.fromJson(Map<String, dynamic> json) {
    if (json['rows'] != null) {
      sjRows = List<SJRows>();
      json['rows'].forEach((v) {
        sjRows.add(SJRows.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = Map<String, dynamic>();
    if (this.sjRows != null) {
      data['rows'] = this.sjRows.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class SJRows {
  int jobId;
  int startDate;
  String startTime;
  String jobName;

  SJRows({this.jobId, this.startDate, this.startTime, this.jobName});

  SJRows.fromJson(Map<String, dynamic> json) {
    jobId = json['JOBID'];
    startDate = json['START_DATE'];
    startTime = json['START_TIME'];
    jobName = json['JOB_NAME'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = Map<String, dynamic>();
    data['JOBID'] = this.jobId;
    data['START_DATE'] = this.startDate;
    data['START_TIME'] = this.startTime;
    data['JOB_NAME'] = this.jobName;
    return data;
  }
}