Json在Dart中解析（颤振）

时间：2020-01-14 14:59:23

标签： json flutter dart

我是Flutter的新手，对复杂的json解析了解不多。我参考了几篇在线文章，但是没有找到合适的解决方案。我的json如下

{
    "EmployeeName":"EmployeeName",
    "Incidents" : [
        {
            "Id":"1",
            "Text":"Text",
            "Photos":[
                {
                    "PhotoUrl" : "http://myphoto.com"
                },
                {
                    "PhotoUrl" : "http://myphoto.com"
                }
            ],
            "Notes" : [
                {
                    "Note":"Note"
                },
                {
                    "Note":"Note"
                }
            ]
        }
    ]
}

任何帮助都会很棒。

4 个答案:

答案 0 :(得分：2)

这是您的json的代码示例：

员工 

class Employee{

String employeeName;
List<Incident> incidents;

Employee({this.employeeName, this.incidents});

Employee.fromJson(Map<String, dynamic> json) {
    employeeName = json['employeeName'];
    if (json['incidents'] != null) {
        incidents = new List<Incident>();
        json['incidents'].forEach((v) {
            incidents.add(new Incident.fromJson(v));
        });
    }
}

Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.employeeName != null) data['employeeName'] = this.employeeName;
    if (this.incidents != null) {
        data['incidents'] = this.incidents.map((v) => v.toJson()).toList();
    }
    return data;
}
}

事件 

class Incident{

String id;
String text;
List<Photo> photos;
List<Note> notes;

Incident({this.id, this.text, this.photos, this.notes});

Incident.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    text = json['text'];
    if (json['photos'] != null) {
        photos = new List<Photo>();
        json['photos'].forEach((v) {
            photos.add(new Photo.fromJson(v));
        });
    }
    if (json['notes'] != null) {
        notes = new List<Note>();
        json['notes'].forEach((v) {
            notes.add(new Note.fromJson(v));
        });
    }
}

Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.id != null) data['id'] = this.id;
    if (this.text != null) data['text'] = this.text;
    if (this.photos != null) {
        data['photos'] = this.photos.map((v) => v.toJson()).toList();
    }
    if (this.notes != null) {
        data['notes'] = this.notes.map((v) => v.toJson()).toList();
    }
    return data;
}
}

注释 

class Note{

String note;

Note({this.note});

Note.fromJson(Map<String, dynamic> json) {
    note = json['note'];
}

Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.note != null) data['note'] = this.note;
    return data;
}
}

照片 

class Photo{

String photoUrl;

Photo({this.photoUrl});

Photo.fromJson(Map<String, dynamic> json) {
    photoUrl = json['photoUrl'];
}

Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.photoUrl != null) data['photoUrl'] = this.photoUrl;
    return data;
}
}

答案 1 :(得分：1)

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:sample_project_for_api/Employee.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  bool _isLoading = false;

  List<Employee> emp = new List();
  @override
  void initState() {
    super.initState();
    getEmployeeDetails();
  }

  Future<String> loadPersonFromAssets() async {
    return await rootBundle.loadString('json/parse.json');
  }

  getEmployeeDetails() async {
    setState(() {
      _isLoading = true;
    });

    String jsonString = await loadPersonFromAssets();
    final employee = employeeFromJson(jsonString);
    emp.add(employee);
    print('This is the employee name : ${employee.employeeName}');
    for (int i = 0; i < employee.incidents.length; i++) {
      print('This is the employee id ${employee.incidents[i].id}');
      print('This is the employee text ${employee.incidents[i].text}');
    }
    for (int i = 0; i < employee.incidents.length; i++) {
      for (int j = 0; j < employee.incidents[i].notes.length; j++) {
        print('This are the notes : ${employee.incidents[i].notes[j].note}');
      }
    }
    setState(() {
      _isLoading = false;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      body: _isLoading == true
          ? CircularProgressIndicator()
          : Container(
              child: ListView.builder(
                itemCount: emp.length,
                itemBuilder: (context, i) {

                  return Card(
                    child: Column(
                      children: <Widget>[
                        Text(emp[i].employeeName),
                        Text(emp[i].incidents[0].id),
                        Text(emp[i].incidents[0].notes[0].note),
                      ],
                    ),
                  );
                },
              ),
            ),
    ));
  }
}

检查您要解析的JSON，我已经给您提供了简单的逻辑，说明了您如何解析。



import 'dart:convert';

Employee employeeFromJson(String str) => Employee.fromJson(json.decode(str));

String employeeToJson(Employee data) => json.encode(data.toJson());

class Employee {
    String employeeName;
    List<Incident> incidents;

    Employee({
        this.employeeName,
        this.incidents,
    });

    factory Employee.fromJson(Map<String, dynamic> json) => Employee(
        employeeName: json["EmployeeName"],
        incidents: List<Incident>.from(json["Incidents"].map((x) => Incident.fromJson(x))),
    );

    Map<String, dynamic> toJson() => {
        "EmployeeName": employeeName,
        "Incidents": List<dynamic>.from(incidents.map((x) => x.toJson())),
    };
}

class Incident {
    String id;
    String text;
    List<Photo> photos;
    List<Note> notes;

    Incident({
        this.id,
        this.text,
        this.photos,
        this.notes,
    });

    factory Incident.fromJson(Map<String, dynamic> json) => Incident(
        id: json["Id"],
        text: json["Text"],
        photos: List<Photo>.from(json["Photos"].map((x) => Photo.fromJson(x))),
        notes: List<Note>.from(json["Notes"].map((x) => Note.fromJson(x))),
    );

    Map<String, dynamic> toJson() => {
        "Id": id,
        "Text": text,
        "Photos": List<dynamic>.from(photos.map((x) => x.toJson())),
        "Notes": List<dynamic>.from(notes.map((x) => x.toJson())),
    };
}

class Note {
    String note;

    Note({
        this.note,
    });

    factory Note.fromJson(Map<String, dynamic> json) => Note(
        note: json["Note"],
    );

    Map<String, dynamic> toJson() => {
        "Note": note,
    };
}

class Photo {
    String photoUrl;

    Photo({
        this.photoUrl,
    });

    factory Photo.fromJson(Map<String, dynamic> json) => Photo(
        photoUrl: json["PhotoUrl"],
    );

    Map<String, dynamic> toJson() => {
        "PhotoUrl": photoUrl,
    };
}

签出要解析的模型。 并如上所述将您的json声明为文件进行解析。

这是最终输出：

I/flutter (23844): This is the employee name : EmployeeName
I/flutter (23844): This is the employee id 1
I/flutter (23844): This is the employee text Text
I/flutter (23844): This are the notes : Note
I/flutter (23844): This are the notes : Note

现在，您将如何使用它在视图中

答案 2 :(得分：1)

您可以使用 https://app.quicktype.io/ 轻松创建类。 JSON 到 Dart > 只需将您的 JSON 粘贴到其中即可享受！

答案 3 :(得分：0)

ma​​in.dart

import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_demo/CategoryListModel.dart';
import 'package:flutter_demo/GetCategoryListParser.dart';
import 'package:fluttertoast/fluttertoast.dart';

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

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

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  List<CategoryListModel> categoryList = <CategoryListModel>[];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Flutter JSON"),
      ),
      body: FutureBuilder(
        future: getCategoryList(),
        builder: (context, snapshot) {
          return categories(categoryList);
        },
      ),
    );
  }

  Widget categories(List<CategoryListModel> list) {
    if (list != null && list.length > 0) {
      return GridView.count(
        crossAxisCount: 3,
        children: List.generate(list.length, (index) {
          return Container(
            child: Column(
              children: [
                Container(
                  child: ClipRRect(
                    child: CachedNetworkImage(
                      fit: BoxFit.fill,
                      imageUrl: list[index].categoryImage,
                    ),
                  ),
                ),
                Text(
                  list[index].categoryName,
                )
              ],
            ),
          );
        }),
      );
    } else {
      return Container();
    }
  }

  Future getCategoryList() async {
    Map result = await GetCategoryListParser.callApi(url);
    if (result["errorCode"] == 0) {
      categoryList = result["value"];
    } else {
      Fluttertoast.showToast(msg: result["value"]);
    }
  }
}

GetParser.dart

import 'dart:async';
import 'dart:convert';

import 'package:flutter_demo/CategoryListModel.dart';
import 'package:http/http.dart' as http;

class GetCategoryListParser {
  static Future callApi(String url) async {
    final response = await http.get(Uri.parse(url)/*, headers: Config.httpGetHeader*/);
    final statusCode = response.statusCode;
    try {
      if (statusCode == 200) {
        Map body = json.decode(response.body);
        List categories = body["Categories"];
        List mainCategories = [];
        for (int i = 0; i < categories.length; i++) {
          Map<String, dynamic> map = categories[i];
          if (map['parent_category_id'] == 0) {
            mainCategories.add(map);
          }
        }
        categories.clear();
        categories.addAll(mainCategories);
        List<CategoryListModel> categoryModelList =
        categories.map((c) => new CategoryListModel.parseForCategories(c)).toList();
        return {
          'errorCode': 0,
          'value': categoryModelList,
        };
      } else {
        return {'errorCode': "-1", 'msg': "Status Code Error"};
      }
    } catch (e) {
      print(e);
      return {'errorCode': "-1", 'msg': "$e"};
    }
  }
}

Model.dart

class CategoryListModel {
  var categoryId, categoryName, categoryImage;

  CategoryListModel.parseForCategories(Map<String, dynamic> map) {
    if (map["id"] != null) {
      categoryId =map["id"];
    }
    if (map["name"] != null) {
      categoryName =map["name"];
    }
    if (map["image"] != null) {
      Map images =map["image"];
      if (images["src"] != null) {
        categoryImage = images["src"];
      }
    }
  }
}
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