flutter - 如何修复 Flutter 期望类型为 'Map' 的值，但得到类型为 'List' 的值

Question

我正在开发一个使用 Flutter Web 和 RESTful API 作为后端的 Web 应用程序。
所以，我正在尝试从 api 中获取数据，使用 Flutter 模型对其进行序列化，然后返回结果。
问题是，我得到了这个结果

Expected a value of type 'Map<String, dynamic>', but got one of type 'List<dynamic>'

如何解决这个问题？
这是我的 flutter 代码:
型号

// To parse this JSON data, do
//
//     final medicalRecordsModel = medicalRecordsModelFromJson(jsonString);

import 'dart:convert';

class MedicalRecordsModel {
  MedicalRecordsModel({
    this.id,
    this.category,
    this.fileName,
    this.dateTimestamp,
    this.description,
    this.upload,
    this.patientName,
    this.age,
    this.address,
    this.userId,
    this.patientId,
    this.isActive,
  });

  final String id;
  final String category;
  final String fileName;
  final String dateTimestamp;
  final String description;
  final String upload;
  final String patientName;
  final String age;
  final String address;
  final dynamic userId;
  final int patientId;
  final bool isActive;

  factory MedicalRecordsModel.fromJson(Map<String, dynamic> json) {
    return MedicalRecordsModel(
      id: json["id"],
      category: json["category"],
      fileName: json["fileName"],
      dateTimestamp: json["dateTimestamp"],
      description: json["description"],
      upload: json["upload"],
      patientName: json["patientName"],
      age: json["age"],
      address: json["address"],
      userId: json["userId"],
      patientId: json["patientId"],
      isActive: json["isActive"],
    );
  }
}

API连接

import 'dart:convert';
import 'dart:developer';
import 'dart:async';
import 'package:app/src/constants/medical_records.dart';
import 'package:app/src/models/medical_records/medical_records.dart';
import 'package:app/src/pages/Medical-Records/medical_record.dart';
import 'package:http/http.dart' as http;

class MedicalRecordsManager {
  var client = http.Client();
  var url = ConstantMedicalRecords.medical_records_api;

  Future<MedicalRecordsModel> getRecords() async {
    var url = ConstantMedicalRecords.medical_records_api;
    log('$url');
    try {
      final response = await client.get(url);
      if (response.statusCode == 200) {
        return MedicalRecordsModel.fromJson(jsonDecode(response.body));
        // print(recordsModel);
      }
    } catch (Exception) {
      print(Exception);
      print("Error occured");
    }
  }
}

这是我想要获取的 JSON 数据

 {
        "id": "103",
        "category": "DOCUMENT",
        "fileName": "Check Up",
        "dateTimestamp": "2021-02-1012:59:46",
        "description": "string",
        "upload": "String",
        "patientName": "1",
        "age": "25",
        "address": "Earth",
        "userId": null,
        "patientId": 12,
        "isActive": true
    }

请帮我解决这个问题。

Answer 1

更改 getRecord如下

Future<MedicalRecordsModel> getRecords() async {
    var url = ConstantMedicalRecords.medical_records_api;
    log('$url');
    try {
      final response = await client.get(url);
      if (response.statusCode == 200) {
        return MedicalRecordsModel.fromJson(jsonDecode(response.body)[0]);
        // print(recordsModel);
      }
    } catch (Exception) {
      print(Exception);
      print("Error occured");
    }
  }

我想 jsonDecode给出 map 列表，因此您的 json map 是该列表的第一个元素。