如何将地图列表中的项目显示到列表视图中
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【中文标题】如何将地图列表中的项目显示到列表视图中【英文标题】：How to display items from a list of maps into a listview 【发布时间】：2020-06-26 13:35:22 【问题描述】：我不知道如何从系统主题或视频请求中显示主题 ID 的值。
我从一个 http 请求获取源到这个 url：https://public.free.beeceptor.com/api
以下是回复。
"body":
"System Topics": [
"Topic ID": "2",
"Title": "Tres",
"Description": "Dos"
,
"Topic ID": "3",
"Title": "Pls Work",
"Description": "nfewtrwe"
,
"Topic ID": "4",
"Title": "Juice",
"Description": "Bar"
],
"Video Requests": [
"Topic ID": "1",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What's you first christmas like?",
"Description": "Please tell me about your Christmas?"
,
"Topic ID": "4",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "5",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "6",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "7",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "8",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "9",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": "From james"
,
"Topic ID": "10",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": "From james"
]
我想像这样将值显示到列表视图中，但直接来自 https 流。
Container(
width: 338,
height: 500.0,
child: ListView.builder(
itemCount: data == null ? 0 : data.length,
itemBuilder: (context, i)
return Container(
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(20.0),
),
height: 74.0,
margin: const EdgeInsets.only(bottom: 10.0),
width: MediaQuery.of(context).size.width,
child: Row(
children: <Widget>[
Container(
child: Text(data[i]["System Topics"]["Topic ID"]),
height: 74.0,
width: 73.0,
decoration: BoxDecoration(
color: Colors.orange,
borderRadius: BorderRadius.only(
topLeft: const Radius.circular(20.0),
bottomLeft: const Radius.circular(20.0)),
),
),
Container(
height: 74.0,
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.only(
topRight: const Radius.circular(20.0),
bottomRight: const Radius.circular(20.0)),
),
width: 265.0,
child: Center(
child: Text(
data[i],
style:
TextStyle(fontSize: 24.0, color: maincolor),
)),
)
],
),
);
,
),
),
我已经解析了 JSON，但是当我尝试将它用作这样的对象时：
文本（问题[i].body.systemTopics.topicid）
它不让我。但是，如果我这样做： questions[i].body.systemTopics 那么它不会抛出错误
【问题讨论】：
你是如何解析 json 的？我认为你需要解析到类。 如果您可以在 dartpad 中设置最小可重现代码，我们可以帮助您修复它。 【参考方案1】：编辑：更新了答案以利用提供的序列化程序 OP 并利用有状态小部件。
请注意，以下代码中的数据是不变的，但您已经对其进行了调整以处理异步 http 请求，因为我想在 dartpad here 中显示答案。
import 'package:flutter/material.dart';
import 'dart:convert';
final Color darkBlue = Color.fromARGB(255, 18, 32, 47);
void main()
runApp(MainWidget());
class MainWidget extends StatelessWidget
@override
Widget build(context)
return MaterialApp(home: Scaffold(body: Questions()));
class Questions extends StatefulWidget
@override
_QuestionsPageState createState() => _QuestionsPageState();
class _QuestionsPageState extends State<Questions>
QuestionModel data;
var users;
String url =
'https://90d53c1e-1ca3-4d5e-982e-0ff81a3ba7f5.mock.pstmn.io/profile/questions';
requestQuestionsAPI()
// final response = await http.get(Uri.encodeFull(url), headers: "Accept": "application/json");
setState(()
//data = json.decode(response.body);
// Isntead of http fecth a constant data
data = questionModelFromJson('''
"body":
"System Topics": [
"Topic ID": "2", "Title": "Tres", "Description": "Dos",
"Topic ID": "3", "Title": "Pls Work", "Description": "nfewtrwe",
"Topic ID": "4", "Title": "Juice", "Description": "Bar"
],
"Video Requests": [
"Topic ID": "1",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What's you first christmas like?",
"Description": "Please tell me about your Christmas?"
,
"Topic ID": "4",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "5",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "6",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "7",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "8",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": ""
,
"Topic ID": "9",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": "From james"
,
"Topic ID": "10",
"From Name": "New User",
"From Email": "dawdw@gmail.com",
"Title": "What is your name?",
"Description": "From james"
]
''');
);
_questions()
requestQuestionsAPI();
void initState()
super.initState();
_questions();
dispose()
super.dispose();
@override
Widget build(BuildContext context)
return MyNewWidget(questionModel: data);
class MyNewWidget extends StatefulWidget
final QuestionModel questionModel;
MyNewWidget(this.questionModel);
@override
_MyNewWidgetState createState() => _MyNewWidgetState();
class _MyNewWidgetState extends State<MyNewWidget>
@override
Widget build(BuildContext context)
print(widget.questionModel);
return MyList(
bodyElement: widget.questionModel.body,
);
class MyList extends StatelessWidget
final Body bodyElement;
MyList(this.bodyElement);
@override
Widget build(BuildContext context)
return Column(children: [
Text(
'Sytem Topics',
style: TextStyle(
fontWeight: FontWeight.bold,
fontSize: 25,
fontStyle: FontStyle.italic),
),
Divider(),
Expanded(
child: ListView.builder(
shrinkWrap: true,
itemCount: bodyElement.systemTopics.length,
itemBuilder: (context, index)
return MyListElement(
id: bodyElement.systemTopics[index].topicId,
description: bodyElement.systemTopics[index].description,
);
),
),
Text(
'Video Requests',
style: TextStyle(
fontWeight: FontWeight.bold,
fontSize: 25,
fontStyle: FontStyle.italic),
),
Divider(),
Expanded(
child: ListView.builder(
shrinkWrap: true,
itemCount: bodyElement.videoRequests.length,
itemBuilder: (context, index)
return MyListElement(
id: bodyElement.videoRequests[index].topicId,
description: bodyElement.videoRequests[index].description,
);
),
)
]);
class MyListElement extends StatelessWidget
final String id;
final String description;
MyListElement(this.id, this.description);
@override
Widget build(BuildContext context)
print('id is $id');
return Container(
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(20.0),
),
height: 74.0,
margin: const EdgeInsets.only(bottom: 10.0),
child: Row(
children: <Widget>[
Container(
alignment: Alignment.center,
child: Text(id),
height: 74.0,
width: 73.0,
decoration: BoxDecoration(
color: Colors.orange,
borderRadius: BorderRadius.only(
topLeft: const Radius.circular(20.0),
bottomLeft: const Radius.circular(20.0)),
),
),
Container(
height: 74.0,
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.only(
topRight: const Radius.circular(20.0),
bottomRight: const Radius.circular(20.0)),
),
width: 265.0,
child: Center(
child: Text(
description,
style: TextStyle(fontSize: 24.0, color: Colors.red),
)),
)
],
),
);
/// Serializers
QuestionModel questionModelFromJson(String str) =>
QuestionModel.fromJson(json.decode(str));
String questionModelToJson(QuestionModel data) => json.encode(data.toJson());
class QuestionModel
Body body;
QuestionModel(
this.body,
);
factory QuestionModel.fromJson(Map<String, dynamic> json) => QuestionModel(
body: Body.fromJson(json["body"]),
);
Map<String, dynamic> toJson() =>
"body": body.toJson(),
;
class Body
List<SystemTopic> systemTopics;
List<VideoRequest> videoRequests;
Body(
this.systemTopics,
this.videoRequests,
);
factory Body.fromJson(Map<String, dynamic> json) => Body(
systemTopics: List<SystemTopic>.from(
json["System Topics"].map((x) => SystemTopic.fromJson(x))),
videoRequests: List<VideoRequest>.from(
json["Video Requests"].map((x) => VideoRequest.fromJson(x))),
);
Map<String, dynamic> toJson() =>
"System Topics":
List<dynamic>.from(systemTopics.map((x) => x.toJson())),
"Video Requests":
List<dynamic>.from(videoRequests.map((x) => x.toJson())),
;
class SystemTopic
String topicId;
String title;
String description;
SystemTopic(
this.topicId,
this.title,
this.description,
);
factory SystemTopic.fromJson(Map<String, dynamic> json) => SystemTopic(
topicId: json["Topic ID"],
title: json["Title"],
description: json["Description"],
);
Map<String, dynamic> toJson() =>
"Topic ID": topicId,
"Title": title,
"Description": description,
;
class VideoRequest
String topicId;
String fromName;
String fromEmail;
String title;
String description;
VideoRequest(
this.topicId,
this.fromName,
this.fromEmail,
this.title,
this.description,
);
factory VideoRequest.fromJson(Map<String, dynamic> json) => VideoRequest(
topicId: json["Topic ID"],
fromName: json["From Name"],
fromEmail: json["From Email"],
title: json["Title"],
description: json["Description"],
);
Map<String, dynamic> toJson() =>
"Topic ID": topicId,
"From Name": fromName,
"From Email": fromEmail,
"Title": title,
"Description": description,
;
对应的输出如下图。
【讨论】：
感谢您的回答，但这对 StatefulWidgets 有何作用？我需要它们，因为 json 数据是从 api 检索的 如果您需要，您必须为传入的 json 编写一个 json 序列化程序。如果您的 api 具有更复杂的结构以及像 this 这样的代码生成器，有很多关于如何进行简单 json 序列化的很好的资源。当前的方法将适用于 StatefulWidget。 所以你已经写好了序列化器。您本可以早点发布它会有所帮助。 :) 无论如何，为了访问有状态小部件的实例变量，您需要像widget.data 和 widget.myvariable 等那样使用它。我会看看是否可以为有状态小部件提供相同的解决方案，但这次使用您的序列化程序.
上面显示的 ui 结果是你所期望的还是别的什么？
我希望这会有所帮助。如果这不能解决您的问题，那么我建议您编辑问题以关注您真正需要的内容。以上是关于如何将地图列表中的项目显示到列表视图中的主要内容，如果未能解决你的问题，请参考以下文章
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