问题是变量类型不匹配，因此您可以继续的一种方法是在工厂方法中将所需类型的字符串数据解析为所有在模式类中声明为非字符串的变量

factory MyClient.fromJson(Map<String, dynamic> json) {
return MyClient(
  id: int.parse(json['id']),
  clientId: int.parse(json['client_id']),
   longitude: double.parse(json['longitude']),
 );

}

这里缺少对象类型。这意味着一些数据来自API字符串。但那是声明为int。显示问题是数据不匹配。

import 'dart:convert';
import 'package:PandeetApp/services/myclient.dart';

class MyClient extends MyClientService {
  final int id, clientId, acceptedBy, pincode;
  final double latitude, longitude;
  final String perpose,
      details,
      when,
      name,
      mobile,
      email,
      orgName,
      address,
      city,
      state,
      country,
      clientIp,
      device,
      createdAt,
      updatedAt;

  MyClient({
    this.id,
    this.clientId,
    this.perpose,
    this.details,
    this.when,
    this.acceptedBy,
    this.name,
    this.mobile,
    this.email,
    this.orgName,
    this.address,
    this.city,
    this.state,
    this.country,
    this.latitude,
    this.longitude,
    this.pincode,
    this.clientIp,
    this.device,
    this.createdAt,
    this.updatedAt,
  });

  factory MyClient.fromJson(Map<String, dynamic> json) {
    return MyClient(
      id: json['id'],
      clientId: json['client_id'],
      perpose: json['perpose'],
      details: json['details'],
      when: json['when'],
      acceptedBy: json['accepted_by'],
      name: json['name'],
      mobile: json['mobile'],
      email: json['email'],
      orgName: json['org_name'],
      address: json['address'],
      city: json['city'],
      state: json['state'],
      pincode: json['pincode'],
      country: json['country'],
      latitude: json['latitude'],
      longitude: json['longitude'],
      clientIp: json['client_ip'],
      device: json['device'],
      createdAt: json['created_at'],
      updatedAt: json['updated_at'],
    );
  }

  Future<List<MyClient>> fetchClients() async {
    var datas = await super.fetchDatas();
    List dataList = json.decode(datas);
    List<MyClient> clients =
        dataList.map((req) => MyClient.fromJson(req)).toList();
    return clients;
  }
}

而不是

import 'dart:convert';
import 'package:PandeetApp/services/myclient.dart';

class MyClient extends MyClientService {
  final int id, clientId, acceptedBy;
  final double latitude, longitude;
  final String perpose,
      details,
      when,
      name,
      mobile,
      email,
      orgName,
      address,
      city,
      state,
      pincode,
      country,
      clientIp,
      device,
      createdAt,
      updatedAt;

  MyClient({
    this.id,
    this.clientId,
    this.perpose,
    this.details,
    this.when,
    this.acceptedBy,
    this.name,
    this.mobile,
    this.email,
    this.orgName,
    this.address,
    this.city,
    this.state,
    this.country,
    this.latitude,
    this.longitude,
    this.pincode,
    this.clientIp,
    this.device,
    this.createdAt,
    this.updatedAt,
  });

  factory MyClient.fromJson(Map<String, dynamic> json) {
    return MyClient(
      id: json['id'],
      clientId: json['client_id'],
      perpose: json['perpose'],
      details: json['details'],
      when: json['when'],
      acceptedBy: json['accepted_by'],
      name: json['name'],
      mobile: json['mobile'],
      email: json['email'],
      orgName: json['org_name'],
      address: json['address'],
      city: json['city'],
      state: json['state'],
      pincode: json['pincode'],
      country: json['country'],
      latitude: json['latitude'],
      longitude: json['longitude'],
      clientIp: json['client_ip'],
      device: json['device'],
      createdAt: json['created_at'],
      updatedAt: json['updated_at'],
    );
  }

  Future<List<MyClient>> fetchClients() async {
    var datas = await super.fetchDatas();
    List dataList = json.decode(datas);
    List<MyClient> clients =
        dataList.map((req) => MyClient.fromJson(req)).toList();
    return clients;
  }
}