获取问题：“\u InternalLinkedHashMap”不是“List”类型的子类型

Question

我试图从API中获取数据，但一直出现此错误。

获取时出现问题：'\u InternalLinkedHashMap

请告诉我如何修复此代码。

模型飞奔

class ComprovanteModel {
  ComprovantesInfoModel jsonResponse;

  String error;

  ComprovanteModel({this.jsonResponse, this.error});

  ComprovanteModel.fromJson(Map<String, dynamic> json)
      : jsonResponse = ComprovantesInfoModel.fromJson(json['json_response']),
        error = '';

  ComprovanteModel.withError(String errorValue)
      : jsonResponse = null,
        error = errorValue;
}

class ComprovanteInfoModel {
  String clientFormalName;
  int volumes;
  int duration;
  CheckpointsModel checkpoint;

  ComprovanteInfoModel({
    this.clientFormalName,
    this.duration,
    this.volumes,
    this.checkpoint,
  });

  ComprovanteInfoModel.fromJson(Map<String, dynamic> json)
      : clientFormalName = json['client_formal_name'],
        checkpoint = CheckpointsModel.fromJson(json['checkpoint']),
        volumes = json['volumes'],
        duration = json['duration'];
}

class CheckpointModel {
  int checkpointId;
  String arrivalTime;
  int status;

  CheckpointModel({
    this.checkpointId,
    this.arrivalTime,
    this.status,
  });

  CheckpointModel.fromJson(Map<String, dynamic> json)
      : checkpointId = json['checkpoint_id'],
        arrivalTime = json['arrival_time'],
        status = json['status'];
}

class CheckpointsModel {
  List<CheckpointModel> checkpoint;

  CheckpointsModel({this.checkpoint});

  CheckpointsModel.fromJson(List<dynamic> jsonList)
      : checkpoint = jsonList.map((e) => CheckpointModel.fromJson(e)).toList();
}

API响应：

{
  "json_response": [
    {
      "client_formal_name": "",
      "deadline": null,
      "volumes": 1,
      "duration": 5,
      "depot_id": 20,
      "service_id": 109856,
      "georef_provider": "ap_geocoder",
      "checkpoint": {
        "checkpoint_id":,
        "arrival_time": "",
        "duration":,
        "status": 1,
        "event_id": 5,
        "resources": [
          {
            "content_type": "PHOTO",
            "service_event_effect_id": 58,
            "content": "em+ndG6XtE2unp",
            "content_label": "",
            "user_effect_unique_code": ""
          },
          {
            "content_type": "RECEPTOR_INFO",
            "service_event_effect_id": 61,
            "content": "{\"user_relationship_unique_code\":\"\",\"is_expected_receiver\":\"true\",\"document\":\"65979973000240\",\"name\":\"",\"description\":\"",\"id\":\"1\"}",
            "content_label": "",
            "user_effect_unique_code": "2"
          }
        ],
        "event_description": "",
        "operation_date": "",
        "obs": "",
        "is_assistant": false,
        "image": "{\"description\": \"Documento\", \"photo\": \""}"
      },
      "final_attendance_window_b": null
    }
  ]
}

我想访问检查点项目，然后访问资源项目（我认为这与检查点的过程相同）。我正在使用列表，但我认为是不正确的，我应该使用地图，但我不知道如何使用。请给我指条路。

Answer 1

>

ComprovanteModel.fromJson(Map<String, dynamic> json)
    : jsonResponse = ComprovantesInfoModel.fromJson(json['json_response']),
      error = '';

对此：

 ComprovanteModel.fromJson(Map<String, dynamic> json)
      : jsonResponse = ComprovantesInfoModel.fromJson(json['json_response'][0]), //added [0] here.
        error = '';

• 如果仔细查看您的响应，它确实有您需要的映射，但此映射实际上位于列表中，请注意“json\u response”中{}周围的方括号[]:[

您需要访问的地图位于此列表的索引[0]处，然后一切都会正常运行。

第二件事是：

 CheckpointsModel.fromJson(List<dynamic> jsonList)
      : checkpoint = jsonList.map((e) => CheckpointModel.fromJson(e)).toList();
}

>

你告诉Flutter你将传递一个类型为List的对象

来回答你的最后一个问题

我想访问检查点项，然后访问资源项（我认为这与检查点的过程相同）。

"资源"：[确实是一个地图列表。在你的代码中，你没有发布你的资源模型，但是我假设你想要一个List

class SingleResourceModel {
   String contentType;
   int serviceId;
   String content;
   String contentLabel;
   String uniqueCode;

  SingleResourceModel({
    this.contentType,
    this.serviceId,
    this.content,
    this.contentLabel,
    this.uniqueCode
  });

  SingleResourceModel.fromJson(Map<String, dynamic> json)
      : contentType = json['content_type'],
        serviceId = json['service_event_effect_id'],
        content = json['content'];
        contentLabel = json['content_label'],
        uniqueCode = json['user_effect_unique_code'];
}
class ListResourceModel {
  List<SingleResourceModel> resourcesList;

  ListResourceModel({this.resourcesList});

  ListResourceModel.fromJson(List<Map<String, dynamic>> jsonList)
      : resourcesList = jsonList.map((e) => SingleResourceModel.fromJson(e)).toList();
}

最后，您可以修改您的检查点模型，并向其添加一个列表资源模型，最终如下所示：

class CheckpointModel {
  int checkpointId;
  String arrivalTime;
  int status;
  ListResourceModel resourcesList;

  CheckpointModel({
    this.checkpointId,
    this.arrivalTime,
    this.status,
    this.resourcesList
  });

  CheckpointModel.fromJson(Map<String, dynamic> json)
      : checkpointId = json['checkpoint_id'],
        arrivalTime = json['arrival_time'],
        status = json['status'],
        resourcesList= json['resources'];    
   }

现在，你应该都准备好了。