我得到这个问题很久以前试图解决这个问题，我看到很多地方在互联网上，但无法解决这个问题，以获得信息从API调用从控制器类.因为这种错误，我看到在docs flutter可能是因为flutter包，也是一个dart包，我得到了SDK 3.0.0这里的代码，请有人帮我实现这个项目非常感谢：
以下是模型类：

class Product {
  int? _totalSize;
  int? _typeId;
  int? _offset;
  late List<ProductModel> _products;
  List<ProductModel> get products => _products;

  Product({required totalSize, required typeId,  required offset, required products}){
    this._totalSize = totalSize;
    this._typeId = typeId;
    this._offset = offset;
    this._products = products;
  }

  factory Product.fromJson(Map<String, dynamic> json) {

    var list = json['products'] as List;
    List<ProductModel> productsList = list.map((e) => ProductModel.fromJson(e as Map<String, dynamic>)).toList();

    return Product(
        totalSize : json['total_size'] as int,
        typeId : json['type_id'] as int,
        offset : json['offset'] as int,
        products: productsList
    );
  }
}

class ProductModel {
  int? id;
  String? name;
  String? description;
  int? price;
  int? stars;
  String? img;
  String? location;
  String? createdAt;
  String? updatedAt;
  int? typeId;

  ProductModel(
      {required this.id,
        required this.name,
        required this.description,
        required this.price,
        required this.stars,
        required this.img,
        required this.location,
        required this.createdAt,
        required this.updatedAt,
        required this.typeId});

  factory ProductModel.fromJson(Map<String, dynamic> json) {
    return ProductModel(
        id: json['id'] as int,
        name: json['name'] as String,
        description: json['description'] as String,
        price: json['price'] as int,
        stars: json['stars'] as int,
        img: json['img'] as String,
        location: json['location'] as String,
        createdAt: json['createdAt'] as String,
        updatedAt: json['updatedAt'] as String,
        typeId: json['typeId'] as int
    );
  }
}

这是控制器类：

import 'dart:convert';

import 'package:get/get.dart';
import 'package:licores_app/data/repository/category_product_repo.dart';

import '../models/products_model.dart';

class CategoryProductController extends GetxController {
  final CategoryProductRepo categoryProductRepo;
  CategoryProductController({required this.categoryProductRepo});

  List<dynamic> _categoryProductList = [];

  // Get Method from Product Model
  List<dynamic> get CategoryProductList => _categoryProductList;

  // Response from repo product method
  Future<void> getCategoryProductList() async {
    Response response =  await categoryProductRepo.getCategoryProductList();

    print('got the products'); // This is right to this point

    if (response.statusCode == 200) {
      // Init to null not to repeat
      _categoryProductList = [];
      _categoryProductList.addAll(Product
          .fromJson(jsonDecode(response.body))
          .products); // --> Here the
      // Unhandled Exception: type 'Null' is not a subtype of type 'String'
      print(_categoryProductList);
      update();
    } else { // I added the curly braces but took off because I was 
       // debugging the problem still persist!
       print('not able to get product list json');
    }
  }
}

这就是错误所在：

[ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: type 'Null' is not a subtype of type 'String'
E/flutter ( 6243): #0      CategoryProductController.getCategoryProductList (package:licores_app/controllers/category_product_controller.dart:27:72)
E/flutter ( 6243): <asynchronous suspension>