Qt平台下使用QJson解析和构建JSON字符串

Posted 2021-10-26 小哈龙

本文转载自：Qt平台下使用QJson解析和构建JSON字符串 - 知乎

原作者总结的很好，受益很大，学习到了

开发平台基于Qt 5.8 Windows。

示例的JSON字符串和上一篇使用的是一样的。

JSON解析示例包括：

• 和风天气实时数据
• 心知天气实时数据
• 心知天气3天预报数据
• 城市空气质量AQI信息
• 全国油价信息
• 北京时间等。

JSON的构建：

• 简单的键值对
• JSON对象作为键的值
• JSON数组
• JSON数组的嵌套

QJson解析JSON示例

JSON的解析要对照JSON字符串来理解，关于JSON字符串的介绍，可以参考JSON简介

首先，解析和构建都要包含如下头文件：

#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>

示例字符串1：和风天气实时数据

这个JSON字符串中HeWeather6键的值是一个数组，数组内只有1个JSON对象，这个对象里又嵌套了几个JSON对象。

{
    "HeWeather6": [{
        "basic": {
            "cid": "CN101010700",
            "location": "昌平",
            "parent_city": "北京",
            "admin_area": "北京",
            "cnty": "中国",
            "lat": "40.21808624",
            "lon": "116.23590851",
            "tz": "+8.00"
        },
        "update": {
            "loc": "2019-07-20 10:21",
            "utc": "2019-07-20 02:21"
        },
        "status": "ok",
        "now": {
            "cloud": "96",
            "cond_code": "104",
            "cond_txt": "阴",
            "fl": "28",
            "hum": "86",
            "pcpn": "0.0",
            "pres": "995",
            "tmp": "25",
            "vis": "4",
            "wind_deg": "100",
            "wind_dir": "东风",
            "wind_sc": "1",
            "wind_spd": "4"
        }
    }]
}

字符串1解析函数

主要是JSON的多层嵌套的解析。

int Parse_HeWeather_Now_Json(void)
{
    QJsonParseError err_rpt;
    QJsonDocument  root_Doc = QJsonDocument::fromJson(he_now_json, &err_rpt);//字符串格式化为JSON

    if(err_rpt.error != QJsonParseError::NoError)
    {
        qDebug() << "JSON格式错误";
        return -1;
    }
    else    //JSON格式正确
    {
        //        qDebug() << "JSON格式正确：\\n" << root_Doc;

        QJsonObject root_Obj = root_Doc.object();
        QJsonValue weather_Value = root_Obj.value("HeWeather6");    //HeWeather6键的值，是一个数组
        if(weather_Value.isArray()) //可省略
        {
            QJsonObject weather_Obj = weather_Value.toArray().at(0).toObject();   //HeWeather6数组就含有一个元素0

            /* basic键信息 */
            QJsonObject basic_Obj = weather_Obj.value("basic").toObject();
            QString cid = basic_Obj.value("cid").toString();
            QString location = basic_Obj.value("location").toString();
            QString parent_city = basic_Obj.value("parent_city").toString();
            QString cnty = basic_Obj.value("cnty").toString();
            QString lat = basic_Obj.value("lat").toString();
            QString lon = basic_Obj.value("lon").toString();
            QString basic_info = cid + " " + parent_city + " " + cnty + " " + lat + " " + lon;
            qDebug() << basic_info;

            /* update键信息 */
            QJsonObject update_Obj = weather_Obj.value("update").toObject();
            QString loc = "当地时间:" + update_Obj.value("loc").toString();   //当地时间
            QString utc = "UTC时间:" + update_Obj.value("utc").toString();   //UTC时间
            QString status = "解析状态:" + weather_Obj.value("status").toString();    //"ok"
            qDebug() << loc + " " + utc + " " + status;

            /* now键信息*/
            QJsonObject now_Obj = weather_Obj.value("now").toObject();
            QString cond_txt = "白天天气:" + now_Obj.value("cond_txt").toString();
            QString hum = "湿度:" + now_Obj.value("hum").toString();
            QString tmp = "温度:" + now_Obj.value("tmp").toString();
            QString wind_dir = "风向:" +  now_Obj.value("wind_dir").toString();
            QString wind_sc = "风级:" + now_Obj.value("wind_sc").toString();
            qDebug() << cond_txt + " " + hum + " " + tmp + " " + wind_dir + " " + wind_sc;
        }
        qDebug() << "解析完成!";
    }
    return 0;
}

示例字符串2：心知天气实时数据

这个字符串和上面那个一样，都是数组元素是JSON对象，对象的值又是一个JSON对象。

{
    "results": [{
        "location": {
            "id": "WX4FBXXFKE4F",
            "name": "北京",
            "country": "CN",
            "path": "北京,北京,中国",
            "timezone": "Asia/Shanghai",
            "timezone_offset": "+08:00"
        },
        "now": {
            "text": "晴",
            "code": "1",
            "temperature": "-7"
        },
        "last_update": "2018-12-06T22:05:00+08:00"
    }]
}

字符串2解析函数

int Parse_Seniverse_Now_Json(void)
{
    QJsonParseError err_rpt;
    QJsonDocument  root_Doc = QJsonDocument::fromJson(seniverse_now_json, &err_rpt);//字符串格式化为JSON
    if(err_rpt.error != QJsonParseError::NoError)
    {
        qDebug() << "JSON格式错误";
        return -1;
    }
    else    //JSON格式正确
    {
        //        qDebug() << "JSON格式正确：\\n" << root_Doc;
        QJsonObject root_Obj = root_Doc.object();
        QJsonValue result_Value = root_Obj.value("results");
        if(result_Value.isArray())
        {
            QJsonObject result_Obj = result_Value.toArray().at(0).toObject();

            QString last_update = result_Obj.value("last_update").toString();
            qDebug() << last_update;

            /* location键的值 */
            QJsonObject location_Obj = result_Obj.value("location").toObject();
            QString id = location_Obj.value("id").toString();
            QString name = location_Obj.value("name").toString();
            QString timezone = location_Obj.value("timezone").toString();
            QString path = location_Obj.value("path").toString();
            QString loc_str = id + " " + name + " " + timezone + " " + path ;
            qDebug() << loc_str;

            /* now键 */
            QJsonObject now_Obj = result_Obj.value("now").toObject();
            QString code = "天气代码: " + now_Obj.value("code").toString();
            QString temperature = "当前温度：" + now_Obj.value("temperature").toString();
            QString text = "天气：" + now_Obj.value("text").toString();
            qDebug() << code << temperature << text;
        }
    }
    return 0;
}

示例字符串3：心知3天天气预报数据

{
    "results": [{
        "location": {
            "id": "WS10730EM8EV",
            "name": "深圳",
            "country": "CN",
            "path": "深圳,深圳,广东,中国",
            "timezone": "Asia/Shanghai",
            "timezone_offset": "+08:00"
        },
        "daily": [{
            "date": "2018-12-06",
            "text_day": "阴",
            "code_day": "9",
            "text_night": "阴",
            "code_night": "9",
            "high": "25",
            "low": "16",
            "precip": "",
            "wind_direction": "无持续风向",
            "wind_direction_degree": "",
            "wind_speed": "10",
            "wind_scale": "2"
        }, {
            "date": "2018-12-07",
            "text_day": "阴",
            "code_day": "9",
            "text_night": "小雨",
            "code_night": "13",
            "high": "20",
            "low": "15",
            "precip": "",
            "wind_direction": "北",
            "wind_direction_degree": "0",
            "wind_speed": "15",
            "wind_scale": "3"
        }, {
            "date": "2018-12-08",
            "text_day": "小雨",
            "code_day": "13",
            "text_night": "小雨",
            "code_night": "13",
            "high": "17",
            "low": "12",
            "precip": "",
            "wind_direction": "东北",
            "wind_direction_degree": "45",
            "wind_speed": "15",
            "wind_scale": "3"
        }],
        "last_update": "2018-12-06T18:00:00+08:00"
    }]
}

字符串3解析函数

int Parse_Seniverse_Forecast_Json(void)
{
    QJsonParseError err_rpt;
    QJsonDocument  root_Doc = QJsonDocument::fromJson(seniverse_forcast_json, &err_rpt);//字符串格式化为JSON
    if(err_rpt.error != QJsonParseError::NoError)
    {
        qDebug() << "JSON格式错误";
        return -1;
    }
    else    //JSON格式正确
    {
        //        qDebug() << "JSON格式正确：\\n" << root_Doc;
        QJsonObject root_Obj = root_Doc.object();
        QJsonValue result_Value = root_Obj.value("results");
        if(result_Value.isArray())
        {
            QJsonObject result_Obj = result_Value.toArray().at(0).toObject();

            QString last_update = result_Obj.value("last_update").toString();
            qDebug() << last_update;
            /* location键的值 */
            QJsonObject location_Obj = result_Obj.value("location").toObject();
            QString id = location_Obj.value("id").toString();
            QString name = location_Obj.value("name").toString();
            QString timezone = location_Obj.value("timezone").toString();
            QString path = location_Obj.value("path").toString();
            QString loc_str = id + " " + name + " " + timezone + " " + path ;
            qDebug() << loc_str;

            /* daily预报天气3天，数组元素3个*/
            QJsonValue daily_Vaule = result_Obj.value("daily");
            if(daily_Vaule.isArray())
            {
                for(int idx = 0; idx <= 2; idx++)
                {
                    QJsonObject daily_Obj = daily_Vaule.toArray().at(idx).toObject();
                    QString date = " 日期：" + daily_Obj.value("date").toString();
                    QString text_day =" 白天天气：" +  daily_Obj.value("text_day").toString();
                    QString high = " 最高温度：" + daily_Obj.value("high").toString();
                    QString low = " 最低温度：" + daily_Obj.value("low").toString();
                    QString wind_direction = " 风向：" + daily_Obj.value("wind_direction").toString();
                    QString wind_scale = " 风级：" + daily_Obj.value("wind_scale").toString();
                    qDebug() << date + text_day + high + low + wind_direction + wind_scale;
                }
            }
        }
    }
    return 0;
}

示例字符串4：空气AQI质量指数

包含10个元素的数组。

{
    "status": "0",
    "citye": "changchun",
    "city": "长春",
    "citycode": "101060101",
    "aqi": "50",
    "data": [{
        "add": "长春",
        "aqi": "50",
        "pm25": "22",
        "per": "优",
        "lv": "1"
    }, {
        "add": "食品厂",
        "aqi": "54",
        "pm25": "18",
        "per": "良",
        "lv": "2"
    }, {
        "add": "客车厂",
        "aqi": "52",
        "pm25": "20",
        "per": "良",
        "lv": "2"
    }, {
        "add": "邮电学院",
        "aqi": "35",
        "pm25": "24",
        "per": "优",
        "lv": "1"
    }, {
        "add": "劳动公园",
        "aqi": "45",
        "pm25": "19",
        "per": "优",
        "lv": "1"
    }, {
        "add": "园林处",
        "aqi": "45",
        "pm25": "21",
        "per": "优",
        "lv": "1"
    }, {
        "add": "净月潭",
        "aqi": "46",
        "pm25": "30",
        "per": "优",
        "lv": "1"
    }, {
        "add": "甩湾子",
        "aqi": "51",
        "pm25": "24",
        "per": "良",
        "lv": "2"
    }, {
        "add": "经开区环卫处",
        "aqi": "48",
        "pm25": "25",
        "per": "优",
        "lv": "1"
    }, {
        "add": "高新区管委会",
        "aqi": "51",
        "pm25": "16",
        "per": "良",
        "lv": "2"
    }, {
        "add": "岱山公园",
        "aqi": "49",
        "pm25": "19",
        "per": "优",
        "lv": "1"
    }]
}

字符串4解析函数

int Parse_AQI_Json(void)
{
    QJsonParseError err_rpt;
    QJsonDocument  root_Doc = QJsonDocument::fromJson(AQI_json, &err_rpt);//字符串格式化为JSON
    if(err_rpt.error != QJsonParseError::NoError)
    {
        qDebug() << "JSON格式错误";
        return -1;
    }
    else    //JSON格式正确
    {
        //        qDebug() << "JSON格式正确：\\n" << root_Doc;
        QJsonObject root_Obj = root_Doc.object();

        QString city = root_Obj.value("city").toString();
        QString citycode = root_Obj.value("citycode").toString();
        QString citye = root_Obj.value("citye").toString();
        QString status = root_Obj.value("status").toString();
        qDebug() << city + " " + citycode + " " + citye + " " + status;

        /* data键 */
        QJsonValue data_Vaule = root_Obj.value("data");
        if(data_Vaule.isArray())
        {
            for(int idx = 0; idx <= 10; idx++)
            {
                QJsonObject data_Obj = data_Vaule.toArray().at(idx).toObject();
                QString add = "地址：" + data_Obj.value("add").toString();
                QString aqi = " AQI：" + data_Obj.value("aqi").toString();
                QString lv = " 空气质量等级：" + data_Obj.value("lv").toString();
                QString per = " 空气质量：" + data_Obj.value("per").toString();
                QString pm25 = " PM2.5等级：" + data_Obj.value("pm25").toString();
                qDebug() << add + aqi + lv + per + pm25;
            }
        }
    }
    return 0;
}

示例字符串5：北京标准时间

比较简单一个JSON对象

{
    "success": "1",
    "result": {
        "timestamp": "1542456793",
        "datetime_1": "2018-11-17 20:13:13",
        "datetime_2": "2018年11月17日 20时13分13秒",
        "week_1": "6",
        "week_2": "星期六",
        "week_3": "周六",
        "week_4": "Saturday"
    }
}

字符串5解析函数

int Parse_BJTime_Json(void)
{
    QJsonParseError err_rpt;
    QJsonDocument  root_Doc = QJsonDocument::fromJson(bj_time_json, &err_rpt);//字符串格式化为JSON
    if(err_rpt.error != QJsonParseError::NoError)
    {
        qDebug() << "JSON格式错误";
        return -1;
    }
    else    //JSON格式正确
    {
        //        qDebug() << "JSON格式正确：\\n" << root_Doc;
        QJsonObject root_Obj = root_Doc.object();

        QString success = root_Obj.value("success").toString();
        /* result键 */
        QJsonObject result_Obj = root_Obj.value("result").toObject();
        QString datetime_1 = result_Obj.value("datetime_1").toString();
        QString datetime_2 = result_Obj.value("datetime_2").toString();
        QString timestamp = result_Obj.value("timestamp").toString();
        QString week_1 = result_Obj.value("week_1").toString();
        QString week_2 = result_Obj.value("week_2").toString();
        QString week_3 = result_Obj.value("week_3").toString();
        QString week_4 = result_Obj.value("week_4").toString();
        qDebug() << datetime_1 << datetime_2;
        qDebug() << week_1 << week_2 << week_3 << week_4;
    }
    return 0;
}

示例字符串6：全国城市油价信息

这种格式的字符串也是标准的JSON字符串，[]表示数组，这个数组内包含了5个字符串：

["北京", "6.78", "7.21", "8.19", "6.45"]

但是这种不是，{}表示对象：

{"北京", "6.78", "7.21", "8.19", "6.45"}

一个数组内包含5个元素，每个元素又是一个数组，每个数组又包含5个字符串，属于数组的嵌套：

{
    "status": "0",
    "msg": "全国各省份汽柴油价格信息",
    "update": "2019-07-21",
    "data": [
        ["地区", "92号", "95号", "98号", "0号柴油"],
        ["北京", "6.78", "7.21", "8.19", "6.45"],
        ["上海", "6.74", "7.17", "7.87", "6.39"],
        ["江苏", "6.75", "7.18", "8.06", "6.37"],
        ["天津", "6.77", "7.15", "8.07", "6.41"]
    ],
    "About": "wcc",
    "Home": "www.wangchaochao.top"
}

字符串6解析函数

//解析数组嵌套的JSON字符串
int Parse_Oil_Price_Json(void)
{
    QJsonParseError err_rpt;
    QJsonDocument  root_Doc = QJsonDocument::fromJson(oil_price_json, &err_rpt);//字符串格式化为JSON
    if(err_rpt.error != QJsonParseError::NoError)
    {
        qDebug() << "JSON格式错误";
        return -1;
    }
    else    //JSON格式正确
    {
        //        qDebug() << "JSON格式正确：\\n" << root_Doc;
        QJsonObject root_Obj = root_Doc.object();

        QString msg = root_Obj.value("msg").toString();
        QString update = root_Obj.value("update").toString();
        QString status = root_Obj.value("status").toString();
        QString About = root_Obj.value("About").toString();
        QString Home = root_Obj.value("Home").toString();
        qDebug() << msg << update << status << About << Home;

        /* data键解析 */
        QJsonValue data_Value = root_Obj.value("data");
        if(data_Value.isArray())    //数组中包含5个数组，每个数组5个字符串元素
        {
            for(int idx = 0; idx <= 4; idx++)
            {
                QJsonValue price_Obj = data_Value.toArray().at(idx);
                if(price_Obj.isArray())
                {
                    QString str1 = price_Obj.toArray().at(0).toString();// 每个元素是一个字符串
                    QString str2 = price_Obj.toArray().at(1).toString();
                    QString str3 = price_Obj.toArray().at(2).toString();
                    QString str4 = price_Obj.toArray().at(3).toString();
                    QString str5 = price_Obj.toArray().at(4).toString();
                    qDebug() << str1 << str2 << str3 << str4 << str5 ;
                }
            }
        }
    }
    return 0;
}

QJson构建JSON示例

1.构建一个简单的键值对JSON

void Create_Simple_JSON(void)
{

    //创建JSON对象
    QJsonObject root_Obj;
    //添加键值对，值的类型自动识别，顺序不可自定义
    root_Obj.insert("CSDN", "https://blog.csdn.net/whik1194");
    root_Obj.insert("cnblogs", "https://home.cnblogs.com/u/whik/");
    root_Obj.insert("Github", "https://github.com/whik/");
    root_Obj.insert("Blog", "https://www.wangchaochao.top/");
    root_Obj.insert("status", 1);
    root_Obj.insert("enable", true);
    root_Obj.insert("update_time", "20190723");

    //创建Json文档
    QJsonDocument root_Doc;
    root_Doc.setObject(root_Obj);
    QByteArray root_str = root_Doc.toJson(QJsonDocument::Compact);  //紧凑格式
//    QByteArray root_str = root_Doc.toJson(QJsonDocument::Indented);   //标准JSON格式    QString strJson(root_str);
    QString strJson(root_str);
    qDebug() << strJson;
}

输出结果

{
    "Blog": "https://www.wangchaochao.top/",
    "CSDN": "https://blog.csdn.net/whik1194",
    "Github": "https://github.com/whik/",
    "cnblogs": "https://home.cnblogs.com/u/whik/",
    "enable": true,
    "status": 1,
    "update_time": "20190723"
}

2.构建北京时间JSON字符串

void Create_BJTime_JSON(void)
{
    QJsonObject result_Obj;
    result_Obj.insert("timestamp", "ok");
    result_Obj.insert("datetime_1", "2019-07-21 10:46:57");
    result_Obj.insert("datetime_2", "2019年07月21日 10时46分57秒");
    result_Obj.insert("week_1", "0");
    result_Obj.insert("week_2", "星期日");
    result_Obj.insert("week_3", "周日");
    result_Obj.insert("week_4", "Sunday");

    QJsonObject root_Obj;
    //添加键值对，值的类型自动识别，顺序不可自定义
    root_Obj.insert("status", "success");
    root_Obj.insert("Blog", "www.wangchaochao.top");
    root_Obj.insert("result", result_Obj);

    //创建Json文档
    QJsonDocument root_Doc;
    root_Doc.setObject(root_Obj);
    QByteArray root_str = root_Doc.toJson(QJsonDocument::Compact);  //紧凑格式
//    QByteArray root_str = root_Doc.toJson(QJsonDocument::Indented);   //标准JSON格式
//    qDebug() << root_str; //中文输出乱码
    QString strJson(root_str);
    qDebug() << strJson;
}

输出结果

{
    "status": "success",
    "result": {
        "timestamp": "ok",
        "datetime_1": "2019-07-21 10:46:57",
        "datetime_2": "2019年07月21日 10时46分57秒",
        "week_1": "0",
        "week_2": "星期日",
        "week_3": "周日",
        "week_4": "Sunday"
    },
    "Blog": "www.wangchaochao.top"
}

3.构建字符串数组

void Create_Array_Str_JSON(void)
{
    QJsonArray root_Arr;

    root_Arr.insert(0, "Sunday");
    root_Arr.insert(1, "Monday");
    root_Arr.insert(2, "Tuesday");
    root_Arr.insert(3, "Wednesday");
    root_Arr.insert(4, "Thursday");
    root_Arr.insert(5, "Friday");
    root_Arr.insert(6, "Saturday");

    //创建Json文档
    QJsonDocument root_Doc;
    root_Doc.setArray(root_Arr);
    QByteArray root_str = root_Doc.toJson(QJsonDocument::Compact);  //紧凑格式
//    QByteArray root_str = root_Doc.toJson(QJsonDocument::Indented);   //标准JSON格式
//    qDebug() << root_str; //中文输出乱码
    QString strJson(root_str);
    qDebug() << strJson;
}

输出结果

["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]

4.构建数组JSON

void Create_Array_JSON(void)
{
    QJsonObject day0_Obj;
    QJsonObject day1_Obj;
    QJsonObject day2_Obj;

    day0_Obj.insert("date", "2019-07-21");
    day0_Obj.insert("cond_txt", "多云");
    day0_Obj.insert("cond_code", "101");
    day0_Obj.insert("hum", "23");
    day0_Obj.insert("tmp_H", "31");
    day0_Obj.insert("tmp_L", "25");

    day1_Obj.insert("date", "2019-07-21");
    day1_Obj.insert("cond_txt", "阵雨");
    day1_Obj.insert("cond_code", "107");
    day1_Obj.insert("hum", "44");
    day1_Obj.insert("tmp_H", "30");
    day1_Obj.insert("tmp_L", "26");

    day2_Obj.insert("date", "2019-07-22");
    day2_Obj.insert("cond_txt", "晴");
    day2_Obj.insert("cond_code", "100");
    day2_Obj.insert("hum", "20");
    day2_Obj.insert("tmp_H", "33");
    day2_Obj.insert("tmp_L", "26");

    QJsonArray weather_Arr;
    weather_Arr.insert(0, day0_Obj);
    weather_Arr.insert(1, day1_Obj);
    weather_Arr.insert(2, day2_Obj);

    QJsonObject root_Obj;
    root_Obj.insert("status", "ok");
    root_Obj.insert("update", "2019-07-21 11:00");
    root_Obj.insert("Blog", "www.wangchaochao.top");
    root_Obj.insert("weather", weather_Arr);    //数组作为weather键的值

    //创建Json文档
    QJsonDocument root_Doc;
    root_Doc.setObject(root_Obj);
    QByteArray root_str = root_Doc.toJson(QJsonDocument::Compact);  //紧凑格式
//    QByteArray root_str = root_Doc.toJson(QJsonDocument::Indented);   //标准JSON格式
//    qDebug() << root_str; //中文输出乱码
    QString strJson(root_str);
    qDebug() << strJson;
}

输出结果

{
    "status": "ok",
    "weather": [{
        "date": "2019-07-21",
        "cond_txt": "多云",
        "cond_code": "101",
        "hum": "23",
        "tmp_H": "31",
        "tmp_L": "25"
    }, {
        "date": "2019-07-22",
        "cond_txt": "晴",
        "cond_code": "100",
        "hum": "20",
        "tmp_H": "33",
        "tmp_L": "26"
    }, {
        "date": "2019-07-23",
        "cond_txt": "阵雨",
        "cond_code": "107",
        "hum": "45",
        "tmp_H": "32",
        "tmp_L": "25"
    }],
    "update": "2019-07-21 11:00",
    "Blog": "www.wangchaochao.top"
}

5.构建数组嵌套的JSON字符串

void Create_Array_Nest_JSON(void)
{
    QJsonArray table_Arr = {"地区", "92号汽油", "95号汽油", "98号汽油", "0号柴油"};
    QJsonArray bj_Arr = {"北京", "6.78", "7.21", "8.19", "6.45"};
    QJsonArray sh_Arr = {"上海", "6.74", "7.17", "7.87", "6.39"};
    QJsonArray js_Arr = {"江苏", "6.75", "7.18", "8.06", "6.37"};
    QJsonArray tj_Arr = {"天津", "6.77", "7.15", "8.07", "6.41"};

    QJsonArray data_Arr;    //数组内嵌套了5个数组
    data_Arr.insert(0, table_Arr);
    data_Arr.insert(1, bj_Arr);
    data_Arr.insert(2, sh_Arr);
    data_Arr.insert(3, js_Arr);
    data_Arr.insert(4, tj_Arr);

    QJsonObject root_Obj;

    root_Obj.insert("status", "ok");
    root_Obj.insert("msg", "全国各省份汽柴油价格信息");
    root_Obj.insert("update", "2019-07-21");
    root_Obj.insert("About", "wcc");
    root_Obj.insert("Blog", "www.wangchaochao.top");
    root_Obj.insert("data", data_Arr);  //数组作为键的值

    //创建Json文档
    QJsonDocument root_Doc;
    root_Doc.setObject(root_Obj);
    QByteArray root_str = root_Doc.toJson(QJsonDocument::Compact);  //紧凑格式
//    QByteArray root_str = root_Doc.toJson(QJsonDocument::Indented);   //标准JSON格式
//    qDebug() << root_str; //中文输出乱码
    QString strJson(root_str);
    qDebug() << strJson;
}

输出结果

{
    "status": "ok",
    "msg": "全国各省份汽柴油价格信息",
    "update": "2019-07-21",
    "data": [
        ["地区", "92号汽油", "95号汽油", "98号汽油", "0号柴油"],
        ["北京", "6.78", "7.21", "8.19", "6.45"],
        ["上海", "6.74", "7.17", "7.87", "6.39"],
        ["江苏", "6.75", "7.18", "8.06", "6.37"],
        ["天津", "6.77", "7.15", "8.07", "6.41"]
    ],
    "About": "wcc",
    "Blog": "www.wangchaochao.top"
}

参考资料

• JSON官方网站：json