如何訪問 json 中的數據

Question

這是我來自 JSON 文件的數據。

[
    {
        "id": "5",
        "msg": {
            "msg": "2121222",
            "sign": "אלמוג שטרית",
            "time": "26/6/2020 16:52",
            "title": "1212"
        }
    },
    {
        "id": "4",
        "msg": {
            "msg": "דשחדש",
            "sign": "אלמוג שטרית",
            "time": " ",
            "title": "בדיקה נ"
        }
    },
    {
        "id": "3",
        "msg": {
            "msg": "21",
            "sign": "אלמוג שטרית",
            "time": "",
            "title": "בדיקה חדשה"
        }
    },
    {
        "id": "2",
        "msg": {
            "msg": "בדיקה חדשה",
            "sign": "אלמוג שטרית",
            "time": "",
            "title": "בדיקה חדשה"
        }
    },
    {
        "id": "1",
        "msg": {
            "msg": "בדיקה",
            "sign": "",
            "time": "",
            "title": "בדיקה"
        }
    }
]

我使用 PHP 從哪個數據庫中提取這些數據。 php 代碼：

$stm = $conn->prepare($query);
$stm->execute();
$rows = $stm->fetchAll(PDO::FETCH_ASSOC);
$js = json_encode($rows, JSON_UNESCAPED_UNICODE);
print $js;

我的問題是如何將“msg”示例中包含的數據訪問到“title”中。

我在 flutter 上的代碼是：

List data;

  Future<String> getData() async {
    var response = await http.get(
        Uri.encodeFull("*myUrl*"),
        headers: {
          "Accept": "application/json"
        }
    );

    this.setState(() {
      data = json.decode(response.body);
    });

    print(data[0]["title"]);

    return "Success!";
  }

Answer 1

看看這個例子：

[
    {
        "id": "5",
        "msg": {
            "msg": "2121222",
            "sign": "אלמוג שטרית",
            "time": "26/6/2020 16:52",
            "title": "1212"
        }
    },
    {
        "id": "4",
        "msg": {
            "msg": "דשחדש",
            "sign": "אלמוג שטרית",
            "time": " ",
            "title": "בדיקה נ"
        }
    },
    {
        "id": "3",
        "msg": {
            "msg": "21",
            "sign": "אלמוג שטרית",
            "time": "",
            "title": "בדיקה חדשה"
        }
    },
    {
        "id": "2",
        "msg": {
            "msg": "בדיקה חדשה",
            "sign": "אלמוג שטרית",
            "time": "",
            "title": "בדיקה חדשה"
        }
    },
    {
        "id": "1",
        "msg": {
            "msg": "בדיקה",
            "sign": "",
            "time": "",
            "title": "בדיקה"
        }
    }
]

以下是您提供的 json 的 model class。

// To parse this JSON data, do
//
//     final yourModel = yourModelFromJson(jsonString);

import 'dart:convert';

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

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

class YourModel {
    YourModel({
        this.id,
        this.msg,
    });

    String id;
    Msg msg;

    factory YourModel.fromJson(Map<String, dynamic> json) => YourModel(
        id: json["id"],
        msg: Msg.fromJson(json["msg"]),
    );

    Map<String, dynamic> toJson() => {
        "id": id,
        "msg": msg.toJson(),
    };
}

class Msg {
    Msg({
        this.msg,
        this.sign,
        this.time,
        this.title,
    });

    String msg;
    String sign;
    String time;
    String title;

    factory Msg.fromJson(Map<String, dynamic> json) => Msg(
        msg: json["msg"],
        sign: json["sign"],
        time: json["time"],
        title: json["title"],
    );

    Map<String, dynamic> toJson() => {
        "msg": msg,
        "sign": sign,
        "time": time,
        "title": title,
    };
}

這是主界面

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:json_parsing_example/models.dart';

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

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

class _MyAppState extends State<MyApp> {
  bool _isLoading = false;
  List<YourModel> yourModel = List();

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

  @override
  void initState() {
    super.initState();
    dataLoadFunction();
  }

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

  /*   String jsonString = await loadFromAssets();
    // i have locally addded the data using the json file you can fetch the api over here.
    final yourdataModel = yourModelFromJson(jsonString);
    yourModel = yourdataModel;

    Instead of this you can use the below as the above is the sample example that i have created for you

    
     */


     /* 
     This is what you should do just add the url and its done.

      var response = await http.get(
        Uri.encodeFull("*myUrl*"),
        headers: {
          "Accept": "application/json"
        }
    );

     final yourdataModel = yourModelFromJson(response.body);
      yourModel = yourdataModel; 
     
      //just uncomment this code and add the url you are good to go.


    */

    setState(() {
      _isLoading = false;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: _isLoading
            ? CircularProgressIndicator()
            : ListView.builder(
                itemCount: yourModel.length,
                shrinkWrap: true,
                itemBuilder: (BuildContext context, int index) {
                  return Card(
                    child: Column(
                      children: <Widget>[
                        Padding(
                          padding: const EdgeInsets.only(top: 10, left: 15),
                          child: Row(
                            children: <Widget>[
                              Text('Message :'),
                              Text(yourModel[index].msg.msg),
                            ],
                          ),
                        ),
                        Divider(
                          color: Colors.grey,
                        ),
                      ],
                    ),
                  );
                },
              ),
      ),
    );
  }
}

只需查看示例並讓我知道它是否有效。

Answer 2

嘗試這個：

print(data['msg']['title'].toString());

或者這個：（如果上面的 Jason Data 不是列表）

print(data[0]['msg']['title'].toString());