Flutter Json 未处理异常：类型“_InternalLinkedHashMap<String, dynamic>”不是“Iterable<dynamic>”类型的子类

Posted 2023-02-23

【中文标题】Flutter Json 未处理异常：类型“_InternalLinkedHashMap<String, dynamic>”不是“Iterable<dynamic>”类型的子类型

【英文标题】：Flutter Json Unhandled Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Iterable<dynamic>'

【发布时间】：2021-08-01 07:17:39

【问题描述】：

类类别 错误：未处理的异常：类型“_InternalLinkedHashMap”不是“Iterable”类型的子类型

  class Category 
  int id;
  String categoryName;
  String seoUrl;


  Category(this.id,this.categoryName,this.seoUrl);

  Category.fromJson(Map json)
    id = json["id"];
    categoryName = json["categoryName"];
    seoUrl = json["seoUrl"];
  

  Map toJson()
    return 
      "id": id,
      "categoryName": categoryName,
      "seoUrl": seoUrl
    ;
  

类主屏幕

错误：未处理的异常：类型“_InternalLinkedHashMap”不是类型“Iterable”的子类型

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:http_demo/data/api/category_api.dart';
import 'package:http_demo/models/category.dart';

class MainScreen extends StatefulWidget 
  @override
  State<StatefulWidget> createState() 
    return MainScreenState();
  


class MainScreenState extends State 
  List<Category> categories = List<Category>();
  List<Widget> categoryWidgets = List<Widget>();

  @override
  void initState() 
    getCategoriesFromApi();
    super.initState();
  

  @override
  Widget build(BuildContext context) 
    return Scaffold(
      appBar: AppBar(
        title: Text(
          "Alışveriş Sistemi",
          style: TextStyle(color: Colors.white),
        ),
        backgroundColor: Colors.blueGrey,
        centerTitle: true,
      ),
      body: Padding(
        padding: EdgeInsets.all(10.0),
        child: Column(
          children: <Widget>[
            SingleChildScrollView(
              scrollDirection: Axis.horizontal,
              child: Row(
                children: categoryWidgets,
              ),
            )
          ],
        ),
      ),
    );
  

  void getCategoriesFromApi() 
    CategoryApi.getCategories().then((response) 
      setState(() 
        Iterable list = json.decode(response.body);
        //categories = list.map((category) => Category.fromJson(category)).toList();
        this.categories = List<Category>.from(list.map((model)=> Category.fromJson(model)));
        getCategoryWidgets();
      );
    );
  

  List<Widget> getCategoryWidgets() 
    for (int i = 0; i < categories.length; i++) 
      categoryWidgets.add(getCategoryWidget(categories[i]));
    
    return categoryWidgets;
  

  Widget getCategoryWidget(Category category) 
    return FlatButton(
      onPressed: null,
      child: Text(
        category.categoryName,
        style: TextStyle(color: Colors.blueGrey),
      ),
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(15.0),
        side: BorderSide(color: Colors.lightGreenAccent),
      ),
    );
  

Error: Unhandled Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Iterable<dynamic>' 错误：未处理的异常：类型“_InternalLinkedHashMap”不是“Iterable”类型的子类型 错误：未处理的异常：类型“_InternalLinkedHashMap”不是“Iterable”类型的子类型 错误：未处理的异常：类型“_InternalLinkedHashMap”不是“Iterable”类型的子类型 错误：未处理的异常：类型“_InternalLinkedHashMap”不是“Iterable”类型的子类型

【参考方案1】：

请检查 JSON 转换后的响应。

void getCategoriesFromApi() 
  CategoryApi.getCategories().then((response) 
    setState(() 
      var list = json.decode(response.body);
      //categories = list.map((category) => Category.fromJson(category)).toList();
      if (list is List) 
        this.categories = list.map((e) => Category.fromJson(e)).toList();
        getCategoryWidgets();
       else 
        print('response is not list');
      
    );
  );

【讨论】：

可以分享一下response.body 吗？

我得到了文本“response is not list” import 'package:http/http.dart' as http;类 CategoryApi 静态未来 getCategories() return http.get("10.0.2.2:3000/category");

是的。您可以检查响应。打印（response.body）；

类类别 int id;字符串类别名称；字符串 seoUrl;类别(this.id,this.categoryName,this.seoUrl); Category.fromJson(Map json) id = json["id"];类别名称 = json["类别名称"]; seoUrl = json["seoUrl"]; Map toJson() return "id": id, "categoryName": categoryName, "seoUrl": seoUrl ;

我正在使用 bluestack。