Null check operator used on a null value The relevant error-causing widget was FutureBuilder<List-CodePudding

I am searching through an api. But I am having error saying null operator used on a null value. I tried all possible method I know. but it looks like I failed to solve the problem. this is my api: https://www.moharaj.com.bd/_public/search/products/hoodie

this is my json data model:

class SearchModel {
  int? id;
  String? name;
  int? merchantId;
  int? categoryId;
  int? subCategoryId;
  Null? brandId;
  Null? subSubCategoryId;
  int? productCode;
  String? shopSku;
  String? slug;
  int? stock;
  String? salePrice;
  int? discount;
  String? price;
  int? alertQuantity;
  String? purchasePrice;
  String? status;
  int? productPlacement;
  int? productPosition;
  Null? campaignId;
  String? details;
  String? thumnail;
  String? discountType;
  String? createdAt;
  String? updatedAt;
  List<ProductImage>? productImage;

  SearchModel(
      {this.id,
      this.name,
      this.merchantId,
      this.categoryId,
      this.subCategoryId,
      this.brandId,
      this.subSubCategoryId,
      this.productCode,
      this.shopSku,
      this.slug,
      this.stock,
      this.salePrice,
      this.discount,
      this.price,
      this.alertQuantity,
      this.purchasePrice,
      this.status,
      this.productPlacement,
      this.productPosition,
      this.campaignId,
      this.details,
      this.thumnail,
      this.discountType,
      this.createdAt,
      this.updatedAt,
      this.productImage});

  SearchModel.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    name = json['name'];
    merchantId = json['merchant_id'];
    categoryId = json['category_id'];
    subCategoryId = json['sub_category_id'];
    brandId = json['brand_id'];
    subSubCategoryId = json['sub_sub_category_id'];
    productCode = json['product_code'];
    shopSku = json['shop_sku'];
    slug = json['slug'];
    stock = json['stock'];
    salePrice = json['sale_price'];
    discount = json['discount'];
    price = json['price'];
    alertQuantity = json['alert_quantity'];
    purchasePrice = json['purchase_price'];
    status = json['status'];
    productPlacement = json['product_placement'];
    productPosition = json['product_position'];
    campaignId = json['campaign_id'];
    details = json['details'];
    thumnail = json['thumnail'];
    discountType = json['discount_type'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
    if (json['product_image'] != null) {
      productImage = <ProductImage>[];
      json['product_image'].forEach((v) {
        productImage!.add(new ProductImage.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['merchant_id'] = this.merchantId;
    data['category_id'] = this.categoryId;
    data['sub_category_id'] = this.subCategoryId;
    data['brand_id'] = this.brandId;
    data['sub_sub_category_id'] = this.subSubCategoryId;
    data['product_code'] = this.productCode;
    data['shop_sku'] = this.shopSku;
    data['slug'] = this.slug;
    data['stock'] = this.stock;
    data['sale_price'] = this.salePrice;
    data['discount'] = this.discount;
    data['price'] = this.price;
    data['alert_quantity'] = this.alertQuantity;
    data['purchase_price'] = this.purchasePrice;
    data['status'] = this.status;
    data['product_placement'] = this.productPlacement;
    data['product_position'] = this.productPosition;
    data['campaign_id'] = this.campaignId;
    data['details'] = this.details;
    data['thumnail'] = this.thumnail;
    data['discount_type'] = this.discountType;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    if (this.productImage != null) {
      data['product_image'] =
          this.productImage!.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class ProductImage {
  int? id;
  int? productId;
  String? productImage;
  String? createdAt;
  String? prefixUrl;
  String? updatedAt;

  ProductImage(
      {this.id,
      this.productId,
      this.productImage,
      this.createdAt,
      this.prefixUrl,
      this.updatedAt});

  ProductImage.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    productId = json['product_id'];
    productImage = json['product_image'];
    createdAt = json['created_at'];
    prefixUrl = json['prefix_url'];
    updatedAt = json['updated_at'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['product_id'] = this.productId;
    data['product_image'] = this.productImage;
    data['created_at'] = this.createdAt;
    data['prefix_url'] = this.prefixUrl;
    data['updated_at'] = this.updatedAt;
    return data;
  }
}

this is json service code:

import 'dart:convert';

import 'package:practice_search_app/SearchModel.dart';
import 'package:http/http.dart' as http;

class SearchService {
  static Future<List<SearchModel>> getData() async {
    final response = await http.get(Uri.parse(
        "https://www.moharaj.com.bd/_public/search/products/samsung"));
    print(response.body);
    var model;

    if (response.statusCode == 200 && response.statusCode == 201) {
      print(response.body);
      List decode = json.decode(response.body);

      model = decode.map((e) => SearchModel.fromJson(e)).toList();

      return model;
    } else {
      return model;
    }
  }
}

this is my view page:

import 'package:flutter/material.dart';
import 'package:practice_search_app/SearchModel.dart';
import 'package:practice_search_app/SearchService.dart';

class SearchResult extends StatefulWidget {
  const SearchResult({Key? key}) : super(key: key);

  @override
  _SearchResultState createState() => _SearchResultState();
}

class _SearchResultState extends State<SearchResult> {
  late Future<List<SearchModel>> getData;
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    getData = SearchService.getData();
  }

  @override
  Widget build(BuildContext context) {
    return SafeArea(
        child: Scaffold(
      body: FutureBuilder<List<SearchModel>>(
        future: getData,
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return ListView.builder(
                itemCount: snapshot.data!.length,
                itemBuilder: (context, index) {
                  var data = snapshot.data![index];
                  return ListTile(
                    title: Text(data.name.toString()),
                    subtitle: Text(data.details.toString()),
                  );
                });
          } else {
            return const Center(child: CircularProgressIndicator.adaptive());
          }
        },
      ),
    ));
  }
}

CodePudding user response：

in getData Function you have wirtten (response.statusCode == 200 && response.statusCode == 201) the && is wrong and should be replaced with || or operation. try this:

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

class SearchModel {
  int? id;
  String? name;
  int? merchantId;
  int? categoryId;
  int? subCategoryId;
  int? brandId;
  Null? subSubCategoryId;
  int? productCode;
  String? shopSku;
  String? slug;
  int? stock;
  String? salePrice;
  int? discount;
  String? price;
  int? alertQuantity;
  String? purchasePrice;
  String? status;
  int? productPlacement;
  int? productPosition;
  Null? campaignId;
  String? details;
  String? thumnail;
  String? discountType;
  String? createdAt;
  String? updatedAt;
  List<ProductImage>? productImage;

  SearchModel(
      {this.id,
      this.name,
      this.merchantId,
      this.categoryId,
      this.subCategoryId,
      this.brandId,
      this.subSubCategoryId,
      this.productCode,
      this.shopSku,
      this.slug,
      this.stock,
      this.salePrice,
      this.discount,
      this.price,
      this.alertQuantity,
      this.purchasePrice,
      this.status,
      this.productPlacement,
      this.productPosition,
      this.campaignId,
      this.details,
      this.thumnail,
      this.discountType,
      this.createdAt,
      this.updatedAt,
      this.productImage});

  SearchModel.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    name = json['name'];
    merchantId = json['merchant_id'];
    categoryId = json['category_id'];
    subCategoryId = json['sub_category_id'];
    brandId = json['brand_id'];
    subSubCategoryId = json['sub_sub_category_id'];
    productCode = json['product_code'];
    shopSku = json['shop_sku'];
    slug = json['slug'];
    stock = json['stock'];
    salePrice = json['sale_price'];
    discount = json['discount'];
    price = json['price'];
    alertQuantity = json['alert_quantity'];
    purchasePrice = json['purchase_price'];
    status = json['status'];
    productPlacement = json['product_placement'];
    productPosition = json['product_position'];
    campaignId = json['campaign_id'];
    details = json['details'];
    thumnail = json['thumnail'];
    discountType = json['discount_type'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
    if (json['product_image'] != null) {
      productImage = <ProductImage>[];
      json['product_image'].forEach((v) {
        productImage!.add(new ProductImage.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['merchant_id'] = this.merchantId;
    data['category_id'] = this.categoryId;
    data['sub_category_id'] = this.subCategoryId;
    data['brand_id'] = this.brandId;
    data['sub_sub_category_id'] = this.subSubCategoryId;
    data['product_code'] = this.productCode;
    data['shop_sku'] = this.shopSku;
    data['slug'] = this.slug;
    data['stock'] = this.stock;
    data['sale_price'] = this.salePrice;
    data['discount'] = this.discount;
    data['price'] = this.price;
    data['alert_quantity'] = this.alertQuantity;
    data['purchase_price'] = this.purchasePrice;
    data['status'] = this.status;
    data['product_placement'] = this.productPlacement;
    data['product_position'] = this.productPosition;
    data['campaign_id'] = this.campaignId;
    data['details'] = this.details;
    data['thumnail'] = this.thumnail;
    data['discount_type'] = this.discountType;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    if (this.productImage != null) {
      data['product_image'] =
          this.productImage!.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class ProductImage {
  int? id;
  int? productId;
  String? productImage;
  String? createdAt;
  String? prefixUrl;
  String? updatedAt;

  ProductImage(
      {this.id,
      this.productId,
      this.productImage,
      this.createdAt,
      this.prefixUrl,
      this.updatedAt});

  ProductImage.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    productId = json['product_id'];
    productImage = json['product_image'];
    createdAt = json['created_at'];
    prefixUrl = json['prefix_url'];
    updatedAt = json['updated_at'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['product_id'] = this.productId;
    data['product_image'] = this.productImage;
    data['created_at'] = this.createdAt;
    data['prefix_url'] = this.prefixUrl;
    data['updated_at'] = this.updatedAt;
    return data;
  }
}

class SearchService {
  static Future<List<SearchModel>> getData() async {
    final response = await http.get(Uri.parse(
        "https://www.moharaj.com.bd/_public/search/products/samsung"));

    if (response.statusCode == 200 || response.statusCode == 201) {
      List decode = json.decode(response.body);

      final model = decode.map((e) => SearchModel.fromJson(e)).toList();

      return model;
    } else {
      return [];
    }
  }
}

void main() {
  runApp(MaterialApp(
    home: SearchResult(),
  ));
}

class SearchResult extends StatefulWidget {
  const SearchResult({Key? key}) : super(key: key);

  @override
  _SearchResultState createState() => _SearchResultState();
}

class _SearchResultState extends State<SearchResult> {
  late Future<List<SearchModel>> getData;
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    getData = SearchService.getData();
  }

  @override
  Widget build(BuildContext context) {
    return SafeArea(
        child: Scaffold(
      body: FutureBuilder<List<SearchModel>>(
        future: getData,
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return ListView.builder(
                itemCount: snapshot.data!.length,
                itemBuilder: (context, index) {
                  var data = snapshot.data![index];
                  return ListTile(
                    title: Text(data.name.toString()),
                    subtitle: Text(data.details.toString()),
                  );
                });
          } else {
            return const Center(child: CircularProgressIndicator.adaptive());
          }
        },
      ),
    ));
  }
}

CodePudding user response：

In your Json service page:

import 'dart:convert';

import 'package:practice_search_app/SearchModel.dart';
import 'package:http/http.dart' as http;

class SearchService {
  static Future<List<SearchModel>> getData() async {
    final response = await http.get(Uri.parse(
        "https://www.moharaj.com.bd/_public/search/products/samsung"));
    print(response.body);
    var model;

    if (response.statusCode == 200 && response.statusCode == 201) {
      print(response.body);
      List decode = json.decode(response.body);
// Here you parse json file in to your model.......So see instruction
      model = decode.map((e) => SearchModel.fromJson(e)).toList();

      return model;
    } else {
      return model;
    }
  }
}

Instruction: 1.In ProductImage.fromJson file you parse Map data so data can't be null so please check carefully which data is null from backend.. 2. Then use Ternary operator to check the null value then assign any empty value with in Json Model...