在顫振中決議動態串列

我正在嘗試決議一個 JSON 資料，該資料進行 API 呼叫，這是一系列包裝在串列中的物件。

[
  {
    "userId": 1,
    "id": 1,
    "title": "quidem molestiae enim"
  },
  {
    "userId": 1,
    "id": 2,
    "title": "sunt qui excepturi placeat culpa"
  },
  {
    "userId": 1,
    "id": 3,
    "title": "omnis laborum odio"
  },
  {
    "userId": 1,
    "id": 4,
    "title": "non esse culpa molestiae omnis sed optio"
  },
  {
    "userId": 1,
    "id": 5,
    "title": "eaque aut omnis a"
  },
  {
    "userId": 1,
    "id": 6,
    "title": "natus impedit quibusdam illo est"
  },
  {
    "userId": 1,
    "id": 7,
    "title": "quibusdam autem aliquid et et quia"
  },
]

這是我希望在其上呈現資料的小部件。我還想知道我是否在我評論的行中正確呼叫了來自 json 回應的資料：

import 'package:flutter/material.dart';
import '../widget/list.dart';
import '../model/data.dart';
import 'package:provider/provider.dart';

class MainScreen extends StatefulWidget {
  @override
  MainScreenState createState() => MainScreenState();
}

class MainScreenState extends State<MainScreen> {

  @override
  void didChangeDependencies() {
    // TODO: implement didChangeDependencies
    Provider.of<DataModel>(context, listen: false).fetchData();
    super.didChangeDependencies();
  }

  @override
  Widget build(BuildContext context) {
    final provider = Provider.of<DataModel>(context).listData;
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
        title: Text("Profile App 2"),
      ),
      body: Padding(
        padding: const EdgeInsets.all(5.0),
        child: ListView.builder(
          itemBuilder: (builder, index) => ListWidget(
            provider[index].userId, //to fetch the userId
            provider[index].id,     //to fetch the id
            provider[index].title   //to fetch the title
          ),
          itemCount: provider.length
        ),
      ),
    );
  }
}

現在，在 DataModel 類中注釋 32:19 和 33:14 的行中拋出錯誤：

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

class Data {
  final int userId;
  final int id;
  final String title;

  Data({
    required this.userId,
    required this.id,
    required this.title
  });
}

class DataModel with ChangeNotifier {
  List<Data> _list = [];

  List<Data> get listData {
    return [..._list];
  }

  Future<void> fetchData() async {
    final url = Uri.parse('https://jsonplaceholder.typicode.com/albums');
    final response = await http.get(url);
    final extractedData = json.decode(response.body);
    print(extractedData);
    Map<String, Data> map = {};
    extractedData.forEach((value) => map.putIfAbsent(  //32:19
        value['id'], () => Data(                       //33:14
        userId: value['userId'],
        id: value['id'],
        title: value['title']
        )
      )
    );
    _list = map as List<Data>;
    notifyListeners();
  }
}   

錯誤：

E/flutter ( 9589): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: type 'int' is not a subtype of type 'String'
E/flutter ( 9589): #0      DataModel.fetchData.<anonymous closure> (package:profile_api_2/model/data.dart:33:14)
E/flutter ( 9589): #1      List.forEach (dart:core-patch/growable_array.dart:403:8)
E/flutter ( 9589): #2      DataModel.fetchData (package:profile_api_2/model/data.dart:32:19)
E/flutter ( 9589): <asynchronous suspension>

uj5u.com熱心網友回復：

改成這樣：

final provider = Provider.of<DataModel>(context, listen: true);
.
.
.
.
//inside your listview builder, do this:

provider.listData[index].userId, //to fetch the userId
itemCount: provider.listData.length

uj5u.com熱心網友回復：

嘗試_list = map.values.toList(); 而不是_list = map as List<Data>現在，您必須使用provider[index].userId代替provider.values.toList()[index].userId.

uj5u.com熱心網友回復：

請更改您id或課程userId領域的資料型別Data。出于某種原因，它無法決議其中一個id或userIdasint或兩者。請通過將資料型別String一一更改來檢查。希望它會起作用。

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