从数组中的数组解析数据并根据 FLUTTER 中映射值的条件创建新列表

Question

[
    {
        "name": "School1",
        "image": "url1",
        "place": "place1",
        "class": [
            {
                "class": "first",
                "strength": "25",
                "students": [
                    {
                        "id": "student1",
                        "dob": "mdd:mm:yyyy",
                        "age": 6,
                        "fees": 0
                    },
                    {
                        "id": "student2",
                        "dob": "mdd:mm:yyyy",
                        "age": 6,
                        "fees": 1
                    }
                ]
            },
            {
                "class": "second",
                "strength": 30,
                "students": [
                    {
                        "id": "student1",
                        "dob": "mdd:mm:yyyy",
                        "age": 6,
                        "fees": 0
                    },
                    {
                        "id": "student2",
                        "dob": "mdd:mm:yyyy",
                        "age": 6,
                        "fees": 1
                    }
                ]
            }
        ]
    },
    {
        "name": "School2",
        "image": "url2",
        "place": "place2",
        "class": [
            {
                "class": "first",
                "strength": "25",
                "students": [
                    {
                        "id": "student1",
                        "dob": "mdd:mm:yyyy",
                        "age": 6,
                        "fees": 0
                    },
                    {
                        "id": "student2",
                        "dob": "mdd:mm:yyyy",
                        "age": 6,
                        "fees": 1
                    }
                ]
            },
            {
                "class": "second",
                "strength": 30,
                "students": [
                    {
                        "id": "student1",
                        "dob": "mdd:mm:yyyy",
                        "age": 6,
                        "fees": 0
                    },
                    {
                        "id": "student2",
                        "dob": "mdd:mm:yyyy",
                        "age": 6,
                        "fees": 1
                    }
                ]
            }
        ]
    }
]

参考以上Json数据

如何在满足FLUTTER/DART中的特定条件后创建添加数据。在这里，我需要单个代码文件中的一些帮助。请帮助我。

将整个数据保存到列表中。
在列表视图中按特定学校的 ID、出生日期和年龄显示学生。
点击学生位置，在另一个屏幕上显示详细信息，如学校名称、class、强度 class、年龄、出生日期。
再创建两个列表视图，根据已付费或未付费情况（数据中已付费=1，未付费=0）显示学生姓名和学校名称。

Answer 1

你的问题需要很长的答案...

我会尽量给你一些提示。首先，根据您的 json 数据创建相应的飞镖类。

我建议你看看：https://app.quicktype.io/ 它是“用任何语言立即解析 json”，您可以将 json 代码放入 dart.

以下是我从您的 json 示例中生成的内容：

   // To parse this JSON data, do
//
//     final school = schoolFromMap(jsonString);

import 'dart:convert';

List<School> schoolFromMap(String str) => List<School>.from(json.decode(str).map((x) => School.fromMap(x)));

String schoolToMap(List<School> data) => json.encode(List<dynamic>.from(data.map((x) => x.toMap())));

class School {
    School({
        this.name,
        this.image,
        this.place,
        this.schoolClass,
    });

    final String name;
    final String image;
    final String place;
    final List<Class> schoolClass;

    School copyWith({
        String name,
        String image,
        String place,
        List<Class> schoolClass,
    }) => 
        School(
            name: name ?? this.name,
            image: image ?? this.image,
            place: place ?? this.place,
            schoolClass: schoolClass ?? this.schoolClass,
        );

    factory School.fromMap(Map<String, dynamic> json) => School(
        name: json["name"] == null ? null : json["name"],
        image: json["image"] == null ? null : json["image"],
        place: json["place"] == null ? null : json["place"],
        schoolClass: json["class"] == null ? null : List<Class>.from(json["class"].map((x) => Class.fromMap(x))),
    );

    Map<String, dynamic> toMap() => {
        "name": name == null ? null : name,
        "image": image == null ? null : image,
        "place": place == null ? null : place,
        "class": schoolClass == null ? null : List<dynamic>.from(schoolClass.map((x) => x.toMap())),
    };
}

class Class {
    Class({
        this.classClass,
        this.strength,
        this.students,
    });

    final String classClass;
    final dynamic strength;
    final List<Student> students;

    Class copyWith({
        String classClass,
        dynamic strength,
        List<Student> students,
    }) => 
        Class(
            classClass: classClass ?? this.classClass,
            strength: strength ?? this.strength,
            students: students ?? this.students,
        );

    factory Class.fromMap(Map<String, dynamic> json) => Class(
        classClass: json["class"] == null ? null : json["class"],
        strength: json["strength"],
        students: json["students"] == null ? null : List<Student>.from(json["students"].map((x) => Student.fromMap(x))),
    );

    Map<String, dynamic> toMap() => {
        "class": classClass == null ? null : classClass,
        "strength": strength,
        "students": students == null ? null : List<dynamic>.from(students.map((x) => x.toMap())),
    };
}

class Student {
    Student({
        this.id,
        this.dob,
        this.age,
        this.fees,
    });

    final String id;
    final String dob;
    final int age;
    final int fees;

    Student copyWith({
        String id,
        String dob,
        int age,
        int fees,
    }) => 
        Student(
            id: id ?? this.id,
            dob: dob ?? this.dob,
            age: age ?? this.age,
            fees: fees ?? this.fees,
        );

    factory Student.fromMap(Map<String, dynamic> json) => Student(
        id: json["id"] == null ? null : json["id"],
        dob: json["dob"] == null ? null : json["dob"],
        age: json["age"] == null ? null : json["age"],
        fees: json["fees"] == null ? null : json["fees"],
    );

    Map<String, dynamic> toMap() => {
        "id": id == null ? null : id,
        "dob": dob == null ? null : dob,
        "age": age == null ? null : age,
        "fees": fees == null ? null : fees,
    };
}

好的，现在你有了模型类。这应该回答您的第 1 点，您可以将欢迎列表保存到 json，反之亦然。

对于第 2 点，您应该使用 ListView.build()，例如使用学生列表（List items = .... ;）：

  @override
  Widget build(BuildContext context) {
    assert(items != null);
    accounts.sort((a, b) => a.id.compareTo(b.id));
    return items.isNotEmpty
        ? ListView.builder(
            padding: const EdgeInsets.all(8),
            itemCount: items.length,
            itemBuilder: (context, counter) => Card(
    child: ListTile(
      onTap: () { // Open a new page/popup to display the student widget....
      },
      title: Text(item.id ?? ''),
      subtitle: Text(item.dob ?? ''),
    ),
          )
        : Container(
            child: Text('No items'),
          );
  }
}

这是用于显示卡片列表的构建方法，显示学生的简单标题 objects。

使用 onTap() {...} 方法显示学生详细信息。

从数组中的数组解析数据并根据 FLUTTER 中映射值的条件创建新列表

Parse data from a array inside array and create new list based on condition of map value in FLUTTER

arrays

flutter

listview

dart

maplist