flutter - 将项目映射到嵌套数组中并将其存储在列表中

Question

这是我的代码

 final List<Dummy> loadedItems = [];
   //dummy data
 final requiredData = {"vendor":"Avatar" ,"grocery_category":[{"category_name":"Fruits", "sub_categories":[{"category_name":"Apple", "items":[{"item_name":"redApple", "item_price":"250"}]}]}]};

loadedItems.add(Dummy(
      title: requiredData['vendor'],
      subtitle: (requiredData['grocery_category'] as List<dynamic>).map((item) {
        Dummy2(item['category_name']);
      }).toList()
    ));

楷模

class Dummy {
  final String title;
  final List<Dummy2> subtitle;

  Dummy({this.title, this.subtitle});
}

class Dummy2 {
  final String subTitle;
  Dummy2(this.subTitle);
}

如果我这样打印

print(loadedItems[0].title);

输出是

Avatar

同样，如果我这样打印，

print(loadedItems[0].subtitle);

输出是

null

我不知道我在做什么错...到目前为止，我已经尝试过，但是找不到为什么会这样。请给我一个解决方案。提前致谢!

Answer 1

您提供的json:

{
    "vendor": "Avatar",
    "grocery_category": [{
        "category_name": "Fruits",
        "sub_categories": [{
            "category_name": "Apple",
            "items": [{
                "item_name": "redApple",
                "item_price": "250"
            }]
        }]
    }]
}

查看此模型以获取json:

// To parse this JSON data, do
//
//     final groceryModel = groceryModelFromJson(jsonString);

import 'dart:convert';

GroceryModel groceryModelFromJson(String str) => GroceryModel.fromJson(json.decode(str));

String groceryModelToJson(GroceryModel data) => json.encode(data.toJson());

class GroceryModel {
    GroceryModel({
        this.vendor,
        this.groceryCategory,
    });

    String vendor;
    List<GroceryCategory> groceryCategory;

    factory GroceryModel.fromJson(Map<String, dynamic> json) => GroceryModel(
        vendor: json["vendor"],
        groceryCategory: List<GroceryCategory>.from(json["grocery_category"].map((x) => GroceryCategory.fromJson(x))),
    );

    Map<String, dynamic> toJson() => {
        "vendor": vendor,
        "grocery_category": List<dynamic>.from(groceryCategory.map((x) => x.toJson())),
    };
}

class GroceryCategory {
    GroceryCategory({
        this.categoryName,
        this.subCategories,
    });

    String categoryName;
    List<SubCategory> subCategories;

    factory GroceryCategory.fromJson(Map<String, dynamic> json) => GroceryCategory(
        categoryName: json["category_name"],
        subCategories: List<SubCategory>.from(json["sub_categories"].map((x) => SubCategory.fromJson(x))),
    );

    Map<String, dynamic> toJson() => {
        "category_name": categoryName,
        "sub_categories": List<dynamic>.from(subCategories.map((x) => x.toJson())),
    };
}

class SubCategory {
    SubCategory({
        this.categoryName,
        this.items,
    });

    String categoryName;
    List<Item> items;

    factory SubCategory.fromJson(Map<String, dynamic> json) => SubCategory(
        categoryName: json["category_name"],
        items: List<Item>.from(json["items"].map((x) => Item.fromJson(x))),
    );

    Map<String, dynamic> toJson() => {
        "category_name": categoryName,
        "items": List<dynamic>.from(items.map((x) => x.toJson())),
    };
}

class Item {
    Item({
        this.itemName,
        this.itemPrice,
    });

    String itemName;
    String itemPrice;

    factory Item.fromJson(Map<String, dynamic> json) => Item(
        itemName: json["item_name"],
        itemPrice: json["item_price"],
    );

    Map<String, dynamic> toJson() => {
        "item_name": itemName,
        "item_price": itemPrice,
    };
}

主页

import 'package:flutter/material.dart';
import 'package:json_parsing_example/models.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: Login());
  }
}

class Login extends StatefulWidget {
  @override
  _LoginState createState() => _LoginState();
}

class _LoginState extends State<Login> {
  List<Grocery> items = List();

  @override
  void initState() {
    super.initState();
    getData();
  }

  getData() async {
    String data =
        await DefaultAssetBundle.of(context).loadString("json/parse.json");

    final grocery = groceryFromJson(data);

    items.add(grocery);
    print(items[0].vendor);
    print(items[0].groceryCategory[0].categoryName);
    print(items[0].groceryCategory[0].subCategories[0].categoryName);
    print(items[0].groceryCategory[0].subCategories[0].items[0].itemName);
    print(items[0].groceryCategory[0].subCategories[0].items[0].itemPrice);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(body: Text('Example'));
  }
}

让我知道是否有效。您可以访问其中的项目。