qt6 通过http查询天气的实现

步骤如下：

cmakelist 当中，增加如下配置
引入包
访问远端api
解析返回的数据
cmakelist 当中，增加如下配置，作用是引入Network库。
2. 引入包

3、访问远端api

cpp 复制代码

void Form1::on_pushButton_clicked()
{
    //根据URL(http://t.weather.itboy.net/api/weather/city/101010100)http请求查询温度信息
    QNetworkAccessManager *manager = new QNetworkAccessManager(this);   //网络管理器
    QNetworkRequest request;   //请求
    request.setUrl(QUrl("http://t.weather.itboy.net/api/weather/city/101010100"));   //设置url
    QNetworkReply *reply = manager->get(request); //发送get请求
    connect(reply, &QNetworkReply::finished, [=](){   //请求完成后的处理
        if(reply->error() == QNetworkReply::NoError)  
        {
            QByteArray data = reply->readAll();
            QJsonParseError json_error;
            QJsonDocument doc = QJsonDocument::fromJson(data, &json_error);  //解析json数据
            if(json_error.error == QJsonParseError::NoError)  
            {
                if(doc.isObject())  
                {
                    QJsonObject obj = doc.object();  //获取json对象
                    if(obj.contains("data"))  //判断是否包含data
                    {
                        QJsonValue value = obj.value("data");  //获取data数据
                        if(value.isObject())
                        {
                            QJsonObject data = value.toObject();  //获取data对象
                            if(data.contains("wendu"))   //判断是否包含wendu
                            {
                                QJsonValue wendu = data.value("wendu");   //获取温度
                                ui->label->setText("温度：" + wendu.toString());  //显示温度
                            }
                        }
                    }
                }
            }
        }
        reply->deleteLater();  //释放资源  这个很重要！！！
    });


}

这段代码是在Qt框架中，特别是使用Qt Network模块，来实现一个HTTP GET请求以查询指定城市的天气温度信息。这里详细解释每一步的作用和目的：

创建QNetworkAccessManager实例：

cpp 复制代码

QNetworkAccessManager *manager = new QNetworkAccessManager(this);

QNetworkAccessManager``是Qt中用于发送网络请求的类。这里创建了一个``QNetworkAccessManager``的实例，并将``this``（假设是某个QWidget或QObject的子类，如``Form1``）作为父对象。这样做可以确保当``Form1``被销毁时，``QNetworkAccessManager``也会被正确地销毁。
3. 设置请求：

cpp 复制代码

QNetworkRequest request; 
request.setUrl(QUrl("http://t.weather.itboy.net/api/weather/city/101010100"));

创建一个QNetworkRequest对象并设置其URL为需要查询的天气API的URL。这里假设URL是正确的，并且服务器会返回JSON格式的天气数据。
5. 发送GET请求：

cpp 复制代码

QNetworkReply *reply = manager->get(request);

通过QNetworkAccessManager的get方法发送GET请求。这个方法返回一个QNetworkReply对象的指针，该对象将用于后续处理HTTP响应。
7. 处理响应 ：

使用connect函数将QNetworkReply的finished信号连接到一个lambda表达式，该表达式在请求完成时执行。

检查错误 ：首先检查响应中是否有错误。如果没有错误（QNetworkReply::NoError），则继续处理数据。
读取并解析JSON数据 ：使用readAll方法读取响应数据，然后尝试使用QJsonDocument::fromJson方法解析这些数据为QJsonDocument对象。解析过程中，QJsonParseError对象用于捕获任何可能的解析错误。
遍历JSON对象 ：解析成功后，检查JSON文档是否是一个对象，并遍历它以查找包含温度信息的data字段。如果找到data字段，并且它是一个对象，则进一步查找wendu（温度）字段。
显示温度 ：如果找到wendu字段，将其值转换为字符串，并设置到UI的某个标签（假设为ui->label）上。

资源释放：

cpp 复制代码

reply->deleteLater();

在lambda表达式的末尾调用deleteLater方法。这是为了确保在lambda表达式执行完毕后，QNetworkReply对象能够被正确地删除。这是因为QNetworkReply对象在响应完成后仍然占用内存，直接删除可能会导致问题，而deleteLater会将其放入事件循环中稍后删除。

注意：

我们图形化界面中 ui->label。
这段代码API返回的数据格式是已知的，

javascript 复制代码

{
    "message": "success感谢又拍云(upyun.com)提供CDN赞助",
    "status": 200,
    "date": "20240703",
    "time": "2024-07-03 19:15:24",
    "cityInfo": {
        "city": "北京市",
        "citykey": "101010100",
        "parent": "北京",
        "updateTime": "15:46"
    },
    "data": {
        "shidu": "51%",
        "pm25": 31.0,
        "pm10": 42.0,
        "quality": "优",
        "wendu": "28.6",
        "ganmao": "各类人群可自由活动",
        "forecast": [
            {
                "date": "03",
                "high": "高温 31℃",
                "low": "低温 17℃",
                "ymd": "2024-07-03",
                "week": "星期三",
                "sunrise": "04:50",
                "sunset": "19:46",
                "aqi": 67,
                "fx": "南风",
                "fl": "2级",
                "type": "晴",
                "notice": "愿你拥有比阳光明媚的心情"
            },
            {
                "date": "04",
                "high": "高温 30℃",
                "low": "低温 21℃",
                "ymd": "2024-07-04",
                "week": "星期四",
                "sunrise": "04:51",
                "sunset": "19:46",
                "aqi": 85,
                "fx": "东南风",
                "fl": "2级",
                "type": "小雨",
                "notice": "雨虽小，注意保暖别感冒"
            },
            {
                "date": "05",
                "high": "高温 32℃",
                "low": "低温 22℃",
                "ymd": "2024-07-05",
                "week": "星期五",
                "sunrise": "04:51",
                "sunset": "19:46",
                "aqi": 94,
                "fx": "西南风",
                "fl": "2级",
                "type": "多云",
                "notice": "阴晴之间，谨防紫外线侵扰"
            },
            {
                "date": "06",
                "high": "高温 29℃",
                "low": "低温 23℃",
                "ymd": "2024-07-06",
                "week": "星期六",
                "sunrise": "04:52",
                "sunset": "19:45",
                "aqi": 84,
                "fx": "东北风",
                "fl": "2级",
                "type": "小雨",
                "notice": "雨虽小，注意保暖别感冒"
            },
            {
                "date": "07",
                "high": "高温 32℃",
                "low": "低温 23℃",
                "ymd": "2024-07-07",
                "week": "星期日",
                "sunrise": "04:53",
                "sunset": "19:45",
                "aqi": 84,
                "fx": "南风",
                "fl": "2级",
                "type": "阴",
                "notice": "不要被阴云遮挡住好心情"
            },
            {
                "date": "08",
                "high": "高温 35℃",
                "low": "低温 23℃",
                "ymd": "2024-07-08",
                "week": "星期一",
                "sunrise": "04:53",
                "sunset": "19:45",
                "aqi": 77,
                "fx": "西南风",
                "fl": "2级",
                "type": "晴",
                "notice": "愿你拥有比阳光明媚的心情"
            },
            {
                "date": "09",
                "high": "高温 34℃",
                "low": "低温 24℃",
                "ymd": "2024-07-09",
                "week": "星期二",
                "sunrise": "04:54",
                "sunset": "19:44",
                "aqi": 62,
                "fx": "东南风",
                "fl": "1级",
                "type": "大雨",
                "notice": "出门最好穿雨衣，勿挡视线"
            },
            {
                "date": "10",
                "high": "高温 34℃",
                "low": "低温 25℃",
                "ymd": "2024-07-10",
                "week": "星期三",
                "sunrise": "04:55",
                "sunset": "19:44",
                "aqi": 61,
                "fx": "东北风",
                "fl": "2级",
                "type": "小雨",
                "notice": "雨虽小，注意保暖别感冒"
            },
            {
                "date": "11",
                "high": "高温 34℃",
                "low": "低温 26℃",
                "ymd": "2024-07-11",
                "week": "星期四",
                "sunrise": "04:55",
                "sunset": "19:44",
                "aqi": 58,
                "fx": "东南风",
                "fl": "2级",
                "type": "多云",
                "notice": "阴晴之间，谨防紫外线侵扰"
            },
            {
                "date": "12",
                "high": "高温 30℃",
                "low": "低温 25℃",
                "ymd": "2024-07-12",
                "week": "星期五",
                "sunrise": "04:56",
                "sunset": "19:43",
                "aqi": 63,
                "fx": "东南风",
                "fl": "2级",
                "type": "阴",
                "notice": "不要被阴云遮挡住好心情"
            },
            {
                "date": "13",
                "high": "高温 35℃",
                "low": "低温 25℃",
                "ymd": "2024-07-13",
                "week": "星期六",
                "sunrise": "04:57",
                "sunset": "19:43",
                "aqi": 47,
                "fx": "东南风",
                "fl": "2级",
                "type": "阴",
                "notice": "不要被阴云遮挡住好心情"
            },
            {
                "date": "14",
                "high": "高温 35℃",
                "low": "低温 25℃",
                "ymd": "2024-07-14",
                "week": "星期日",
                "sunrise": "04:57",
                "sunset": "19:42",
                "aqi": 66,
                "fx": "东南风",
                "fl": "2级",
                "type": "多云",
                "notice": "阴晴之间，谨防紫外线侵扰"
            },
            {
                "date": "15",
                "high": "高温 32℃",
                "low": "低温 23℃",
                "ymd": "2024-07-15",
                "week": "星期一",
                "sunrise": "04:58",
                "sunset": "19:42",
                "aqi": 61,
                "fx": "东风",
                "fl": "2级",
                "type": "中雨",
                "notice": "记得随身携带雨伞哦"
            },
            {
                "date": "16",
                "high": "高温 30℃",
                "low": "低温 21℃",
                "ymd": "2024-07-16",
                "week": "星期二",
                "sunrise": "04:59",
                "sunset": "19:41",
                "aqi": 54,
                "fx": "东风",
                "fl": "2级",
                "type": "中雨",
                "notice": "记得随身携带雨伞哦"
            },
            {
                "date": "17",
                "high": "高温 35℃",
                "low": "低温 23℃",
                "ymd": "2024-07-17",
                "week": "星期三",
                "sunrise": "05:00",
                "sunset": "19:40",
                "aqi": 46,
                "fx": "西南风",
                "fl": "2级",
                "type": "多云",
                "notice": "阴晴之间，谨防紫外线侵扰"
            }
        ],
        "yesterday": {
            "date": "02",
            "high": "高温 25℃",
            "low": "低温 17℃",
            "ymd": "2024-07-02",
            "week": "星期二",
            "sunrise": "04:50",
            "sunset": "19:46",
            "aqi": 25,
            "fx": "北风",
            "fl": "2级",
            "type": "小雨",
            "notice": "雨虽小，注意保暖别感冒"
        }
    }
}

由于网络请求是异步的，用户界面不会阻塞，这提供了更好的用户体验。槽函数在这里功不可没！另外感谢哈工程大学通讯专业的同学，上面代码不是我写的：)