如何从 Flutter 中的 JSON 文件中获取所有命令 id？

Posted 2023-02-23

技术标签:

【中文标题】如何从 Flutter 中的 JSON 文件中获取所有命令 id？【英文标题】：How can i get all the commands id from a JSON file in flutter? 【发布时间】：2020-05-26 00:36:28 【问题描述】：

我是颤振的初学者，我正在尝试使用颤振从 JSON 文件中获取值。我可以获得一些设备 ID 和设备名称的值，但我真的不知道如何在命令中获取 ID。预先感谢您的帮助。

这是我的 JSON 文件：

[
    
        "id": "15622bf9-969c-4f54-bd80-265a8132c97a",
        "name": "Random-Integer-Generator01",
        "adminState": "UNLOCKED",
        "operatingState": "ENABLED",
        "lastConnected": 0,
        "lastReported": 0,
        "labels": [
            "device-random-example"
        ],
        "location": null,
        "commands": [
            
                "created": 1572962679310,
                "modified": 1572962679310,
                "id": "f07b4a42-4358-4394-bc71-76f292f8359f",
                "name": "GenerateRandomValue_Int8",
                "get": 
                    "path": "/api/v1/device/deviceId/GenerateRandomValue_Int8",
                    "responses": [
                        
                            "code": "503",
                            "description": "service unavailable"
                        
                    ],
                    "url": "http://edgex-core-command:48082/api/v1/device/15622bf9-969c-4f54-bd80-265a8132c97a/command/f07b4a42-4358-4394-bc71-76f292f8359f"
                ,
                "put": 
                    "path": "/api/v1/device/deviceId/GenerateRandomValue_Int8",
                    "parameterNames": [
                        "Min_Int8",
                        "Max_Int8"
                    ],
                    "url": "http://edgex-core-command:48082/api/v1/device/15622bf9-969c-4f54-bd80-265a8132c97a/command/f07b4a42-4358-4394-bc71-76f292f8359f"
                
            ,
            
                "created": 1572962679336,
                "modified": 1572962679336,
                "id": "86eafeb6-f359-40e7-b6c1-d35e9e9eb625",
                "name": "GenerateRandomValue_Int16",
                "get": 
                    "path": "/api/v1/device/deviceId/GenerateRandomValue_Int16",
                    "responses": [
                        
                            "code": "503",
                            "description": "service unavailable"
                        
                    ],
                    "url": "http://edgex-core-command:48082/api/v1/device/15622bf9-969c-4f54-bd80-265a8132c97a/command/86eafeb6-f359-40e7-b6c1-d35e9e9eb625"
                ,
                "put": 
                    "path": "/api/v1/device/deviceId/GenerateRandomValue_Int16",
                    "parameterNames": [
                        "Min_Int16",
                        "Max_Int16"
                    ],
                    "url": "http://edgex-core-command:48082/api/v1/device/15622bf9-969c-4f54-bd80-265a8132c97a/command/86eafeb6-f359-40e7-b6c1-d35e9e9eb625"
                
            ,
            
                "created": 1572962679337,
                "modified": 1572962679337,
                "id": "bb492384-8c72-4ab6-9a84-24a3be0b934e",
                "name": "GenerateRandomValue_Int32",
                "get": 
                    "path": "/api/v1/device/deviceId/GenerateRandomValue_Int32",
                    "responses": [
                        
                            "code": "503",
                            "description": "service unavailable"
                        
                    ],
                    "url": "http://edgex-core-command:48082/api/v1/device/15622bf9-969c-4f54-bd80-265a8132c97a/command/bb492384-8c72-4ab6-9a84-24a3be0b934e"
                ,
                "put": 
                    "path": "/api/v1/device/deviceId/GenerateRandomValue_Int32",
                    "parameterNames": [
                        "Min_Int32",
                        "Max_Int32"
                    ],
                    "url": "http://edgex-core-command:48082/api/v1/device/15622bf9-969c-4f54-bd80-265a8132c97a/command/bb492384-8c72-4ab6-9a84-24a3be0b934e"
                
            
        ]
    ,
    
        "id": "97dcd3b2-f4f1-4a1a-9520-2ff62c697945",
        "name": "Random-Boolean-Device",
        "adminState": "UNLOCKED",
        "operatingState": "ENABLED",
        "lastConnected": 0,
        "lastReported": 0,
        "labels": [
            "device-virtual-example"
        ],
        "location": null,
        "commands": [
            
                "created": 1572962679576,
                "modified": 1572962679576,
                "id": "1bc520ef-a9a4-43c7-8098-dcc5faea9ea1",
                "name": "RandomValue_Bool",
                "get": 
                    "path": "/api/v1/device/deviceId/RandomValue_Bool",
                    "responses": [
                        
                            "code": "503",
                            "description": "service unavailable"
                        
                    ],
                    "url": "http://edgex-core-command:48082/api/v1/device/97dcd3b2-f4f1-4a1a-9520-2ff62c697945/command/1bc520ef-a9a4-43c7-8098-dcc5faea9ea1"
                ,
                "put": 
                    "path": "/api/v1/device/deviceId/RandomValue_Bool",
                    "parameterNames": [
                        "RandomValue_Bool",
                        "EnableRandomization_Bool"
                    ],
                    "url": "http://edgex-core-command:48082/api/v1/device/97dcd3b2-f4f1-4a1a-9520-2ff62c697945/command/1bc520ef-a9a4-43c7-8098-dcc5faea9ea1"
                
            
        ]
    ,
]

这是我的主要颤振代码：

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

import 'GET.dart';
import 'Device.dart';

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

class MyApp extends StatelessWidget 
  @override
  build(context) 
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'My Http App',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyListScreen(),
    );
  


class MyListScreen extends StatefulWidget 
  @override
  createState() => _MyListScreenState();


class _MyListScreenState extends State 
  var device = new List<Device>();

  _getDevice() 
    GET.getDevice().then((response) 
      setState(() 
        Iterable list = json.decode(response.body);
        device = list.map((model) => Device.fromJson(model)).toList();
      );
    );
  

  initState() 
    super.initState();
    _getDevice();
  

  dispose() 
    super.dispose();
  

  @override
  build(context) 
    return Scaffold(
        appBar: AppBar(
          title: Text("Device List"),
        ),
        body: ListView.builder(
          itemCount: device.length,
          itemBuilder: (context, index) 
            return ListTile(title: Text("Num $index "+device[index].id));
          ,
        ));

这是我的设备类：

class Device 
  //String 
  String id;
  String name;
  //String commands;

  Device(String id, String name) 
    this.id = id;
    this.name = name;
    //this.commands = commands; 
    //this.email = email;
  

  Device.fromJson(Map json)
      : id = json['id'],
        name = json['name'];
        // commands = json['commands'];
        //['commands'][0]['name'], // marche

        //email = json['email'];

  Map toJson() 
    return 'id': id, 'name': name;

【问题讨论】：

【参考方案1】：

您可以使用下面的类转换 json 并使用 device[index].commands 获取设备命令

class Device 
  String id;
  String name;
  String adminState;
  String operatingState;
  int lastConnected;
  int lastReported;
  List<String> labels;
  Null location;
  List<Commands> commands;

  Device(
      this.id,
      this.name,
      this.adminState,
      this.operatingState,
      this.lastConnected,
      this.lastReported,
      this.labels,
      this.location,
      this.commands);

  Device.fromJson(Map<String, dynamic> json) 
    id = json['id'];
    name = json['name'];
    adminState = json['adminState'];
    operatingState = json['operatingState'];
    lastConnected = json['lastConnected'];
    lastReported = json['lastReported'];
    labels = json['labels'].cast<String>();
    location = json['location'];
    if (json['commands'] != null) 
      commands = new List<Commands>();
      json['commands'].forEach((v) 
        commands.add(new Commands.fromJson(v));
      );
    
  

  Map<String, dynamic> toJson() 
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['adminState'] = this.adminState;
    data['operatingState'] = this.operatingState;
    data['lastConnected'] = this.lastConnected;
    data['lastReported'] = this.lastReported;
    data['labels'] = this.labels;
    data['location'] = this.location;
    if (this.commands != null) 
      data['commands'] = this.commands.map((v) => v.toJson()).toList();
    
    return data;
  


class Commands 
  int created;
  int modified;
  String id;
  String name;
  Get get;
  Put put;

  Commands(
      this.created, this.modified, this.id, this.name, this.get, this.put);

  Commands.fromJson(Map<String, dynamic> json) 
    created = json['created'];
    modified = json['modified'];
    id = json['id'];
    name = json['name'];
    get = json['get'] != null ? new Get.fromJson(json['get']) : null;
    put = json['put'] != null ? new Put.fromJson(json['put']) : null;
  

  Map<String, dynamic> toJson() 
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['created'] = this.created;
    data['modified'] = this.modified;
    data['id'] = this.id;
    data['name'] = this.name;
    if (this.get != null) 
      data['get'] = this.get.toJson();
    
    if (this.put != null) 
      data['put'] = this.put.toJson();
    
    return data;
  


class Get 
  String path;
  List<Responses> responses;
  String url;

  Get(this.path, this.responses, this.url);

  Get.fromJson(Map<String, dynamic> json) 
    path = json['path'];
    if (json['responses'] != null) 
      responses = new List<Responses>();
      json['responses'].forEach((v) 
        responses.add(new Responses.fromJson(v));
      );
    
    url = json['url'];
  

  Map<String, dynamic> toJson() 
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['path'] = this.path;
    if (this.responses != null) 
      data['responses'] = this.responses.map((v) => v.toJson()).toList();
    
    data['url'] = this.url;
    return data;
  


class Responses 
  String code;
  String description;

  Responses(this.code, this.description);

  Responses.fromJson(Map<String, dynamic> json) 
    code = json['code'];
    description = json['description'];
  

  Map<String, dynamic> toJson() 
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['code'] = this.code;
    data['description'] = this.description;
    return data;
  


class Put 
  String path;
  List<String> parameterNames;
  String url;

  Put(this.path, this.parameterNames, this.url);

  Put.fromJson(Map<String, dynamic> json) 
    path = json['path'];
    parameterNames = json['parameterNames'].cast<String>();
    url = json['url'];
  

  Map<String, dynamic> toJson() 
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['path'] = this.path;
    data['parameterNames'] = this.parameterNames;
    data['url'] = this.url;
    return data;

【讨论】：

感谢您的回答，我会尝试您的解决方案。

以上是关于如何从 Flutter 中的 JSON 文件中获取所有命令 id？的主要内容，如果未能解决你的问题，请参考以下文章

如何从服务器上的 php 文件中获取 json 数据到 Flutter 应用程序

从flutter中的多个嵌套json数组中获取值

在flutter中获取JSON数据返回NULL

如何从 Flutter 中的 Firebase 实时数据库中按 categoryId 获取产品？

Flutter：如何从 Firebase 通知负载中获取 Json 数据

Flutter 中如何从这个 Json 中获取数据？