Flutter：如何在 ListView.builder 中显示来自 ListView.builder 的数组数据？

Question

我有一个这样的 JSON 文件：

[
  {
    "id": 1,
    "continent": "North America",
    "country": [
      {
        "name": "United States",
        "capital": "Washington, D.C.",
        "language": [
          "English"
        ]
      },
      {
        "name": "Canada",
        "capital": "Ottawa",
        "language": [
          "English",
          "French"
        ]
      }
    ]
  },
  {
    "id": 2,
    "continent": "Europe",
    "country": [
      {
        "name": "Germany",
        "capital": "Berlin",
        "language": [
          "German"
        ]
      }
    ]
  }
]

我使用https://app.quicktype.io/ 来解析 JSON 数据。 我创建了一个ListView.builder 来显示大陆的名称。 现在我想显示每个大陆的“国家名称”、“首都”和“语言”。

所以请帮我这样做，这是主文件

import 'package:flutter/material.dart';
import 'model/continent_model.dart';
import 'services/continent_services.dart';

class ContinentPage extends StatefulWidget {
  ContinentPage() : super();
  @override
  _ContinentPageState createState() => _ContinentPageState();
}

class _ContinentPageState extends State<ContinentPage> {
  List<Continent> _continent;
  List<Country> _country;

  @override
  void initState() {
    super.initState();
    ContinentServices.getContinent().then((continents) {
      setState(() {
        _continent = continents;
      });
    });
  }

  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(),
        body: Container(
            child: ListView.builder(
                itemCount: null == _continent ? 0 : _continent.length,
                itemBuilder: (context, index) {
                  return Row(
                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
                    children: <Widget>[
                      Text(_continent[index].continent),
                      // how to create a ListView show a Column that includes:
                      // _country[index].name,
                      // _country[index].capital,
                      // _country[index].language,
                    ],
                  );
                })));
  }
}

Answer 1

您需要将第二个 listview.builder 放置在具有定义高度的容器内。

Container(
  height: 120,
  child: ListView.builder(
    shrinkWrap: true,
    scrollDirection: Axis.horizontal,
    itemCount: map.length,
    itemBuilder: (context, index) => Column(
      children: [
        Text(_country.elementAt(index).name),
        Text(_country.elementAt(index).capital),
Text(_country.elementAt(index).language),
      ],
    ),
  ),
)

Answer 2

您可以在下面复制粘贴运行完整代码
您可以使用嵌套的ListView.separated
代码sn-p

ListView.separated(
            separatorBuilder: (BuildContext context, int index) {
              return SizedBox(
                height: 10,
              );
            },
            shrinkWrap: true,
            itemCount: null == _continent ? 0 : _continent.length,
            itemBuilder: (context, index) {
              return Column(
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: <Widget>[
                  Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: <Widget>[
                        Expanded(
                            flex: 1, child: Text(_continent[index].continent)),
                        Expanded(
                          flex: 2,
                          child: Container(
                            height: 50,
                            child: ListView.separated(
                                separatorBuilder:

详细描述太长了，可以直接参考完整代码

工作演示

完整代码

import 'package:flutter/material.dart';
// To parse this JSON data, do
//
//     final continent = continentFromJson(jsonString);

import 'dart:convert';

List<Continent> continentFromJson(String str) =>
    List<Continent>.from(json.decode(str).map((x) => Continent.fromJson(x)));

String continentToJson(List<Continent> data) =>
    json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class Continent {
  Continent({
    this.id,
    this.continent,
    this.country,
  });

  int id;
  String continent;
  List<Country> country;

  factory Continent.fromJson(Map<String, dynamic> json) => Continent(
        id: json["id"],
        continent: json["continent"],
        country:
            List<Country>.from(json["country"].map((x) => Country.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "continent": continent,
        "country": List<dynamic>.from(country.map((x) => x.toJson())),
      };
}

class Country {
  Country({
    this.name,
    this.capital,
    this.language,
  });

  String name;
  String capital;
  List<String> language;

  factory Country.fromJson(Map<String, dynamic> json) => Country(
        name: json["name"],
        capital: json["capital"],
        language: List<String>.from(json["language"].map((x) => x)),
      );

  Map<String, dynamic> toJson() => {
        "name": name,
        "capital": capital,
        "language": List<dynamic>.from(language.map((x) => x)),
      };
}

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class ContinentServices {
  Future<List<Continent>> getContinent() {
    String jsonString = '''
    [
  {
    "id": 1,
    "continent": "North America",
    "country": [
      {
        "name": "United States",
        "capital": "Washington, D.C.",
        "language": [
          "English"
        ]
      },
      {
        "name": "Canada",
        "capital": "Ottawa",
        "language": [
          "English",
          "French"
        ]
      }
    ]
  },
  {
    "id": 2,
    "continent": "Europe",
    "country": [
      {
        "name": "Germany",
        "capital": "Berlin",
        "language": [
          "German"
        ]
      }
    ]
  }
]
    ''';
    List<Continent> continentList = continentFromJson(jsonString);
    return Future.value(continentList);
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  List<Continent> _continent;

  @override
  void initState() {
    super.initState();
    ContinentServices().getContinent().then((continents) {
      setState(() {
        _continent = continents;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: ListView.separated(
            separatorBuilder: (BuildContext context, int index) {
              return SizedBox(
                height: 10,
              );
            },
            shrinkWrap: true,
            itemCount: null == _continent ? 0 : _continent.length,
            itemBuilder: (context, index) {
              return Column(
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: <Widget>[
                  Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: <Widget>[
                        Expanded(
                            flex: 1, child: Text(_continent[index].continent)),
                        Expanded(
                          flex: 2,
                          child: Container(
                            height: 50,
                            child: ListView.separated(
                                separatorBuilder:
                                    (BuildContext context, int index) {
                                  return SizedBox(
                                    width: 10,
                                  );
                                },
                                shrinkWrap: true,
                                scrollDirection: Axis.horizontal,
                                itemCount: null == _continent
                                    ? 0
                                    : _continent[index].country.length,
                                itemBuilder: (context, countryIndex) {
                                  print(_continent[index]
                                      .country[countryIndex]
                                      .name);
                                  return Row(
                                      mainAxisAlignment:
                                          MainAxisAlignment.center,
                                      crossAxisAlignment:
                                          CrossAxisAlignment.center,
                                      children: <Widget>[
                                        Container(
                                          width: 120,
                                          child: Column(
                                            children: <Widget>[
                                              Text(
                                                _continent[index]
                                                    .country[countryIndex]
                                                    .name,
                                                style: TextStyle(
                                                    color: Colors.red),
                                              ),
                                              Text(
                                                  _continent[index]
                                                      .country[countryIndex]
                                                      .capital,
                                                  style: TextStyle(
                                                      color: Colors.red)),
                                              Expanded(
                                                child: ListView.separated(
                                                    separatorBuilder:
                                                        (BuildContext context,
                                                            int index) {
                                                      return SizedBox(
                                                        width: 2,
                                                      );
                                                    },
                                                    shrinkWrap: true,
                                                    scrollDirection:
                                                        Axis.horizontal,
                                                    itemCount: null ==
                                                            _continent
                                                        ? 0
                                                        : _continent[index]
                                                            .country[
                                                                countryIndex]
                                                            .language
                                                            .length,
                                                    itemBuilder: (context,
                                                        languageIndex) {
                                                      return Row(
                                                          mainAxisAlignment:
                                                              MainAxisAlignment
                                                                  .spaceEvenly,
                                                          children: <Widget>[
                                                            Text(
                                                                _continent[index]
                                                                        .country[
                                                                            countryIndex]
                                                                        .language[
                                                                    languageIndex],
                                                                style: TextStyle(
                                                                    color: Colors
                                                                        .red)),
                                                          ]);
                                                    }),
                                              ),
                                            ],
                                          ),
                                        )
                                      ]);
                                }),
                          ),
                        )
                      ])
                ],
              );
            }));
  }
}