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

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urlQNetworkReply *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：
```
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。
设置请求：
```
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。
发送GET请求：
```
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。
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：
```
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，

{"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"}}
}