qt http 下载文件

在Qt中使用HTTP协议下载文件，可以使用Qt提供的网络模块，通过QNetworkAccessManager和QNetworkRequest类实现。

具体步骤如下：

QNetworkAccessManager* manager = new QNetworkAccessManager(this);
创建QNetworkRequest对象，设置下载文件的URL地址。
QUrl url("http://example.com/downloadfile.zip");
QNetworkRequest request(url);
发送HTTP请求并接收响应数据。
QNetworkReply* reply = manager->get(request);
连接QNetworkReply的finished()信号，当HTTP请求完成后触发该信号，可以在槽函数中读取下载的文件数据。
connect(reply, &QNetworkReply::finished, this, &MyClass::downloadFinished);
在downloadFinished槽函数中读取下载的文件数据，并保存到本地文件中。
void MyClass::downloadFinished()
    QNetworkReply* reply = qobject_cast<QNetworkReply*>(sender());
    if(reply)
        if(reply->error() == QNetworkReply::NoError)
            QString fileName = "downloadfile.zip";
            QFile file(fileName);
            if(file.open(QIODevice::WriteOnly))
                file.write(reply->readAll());
                file.close();
        reply->deleteLater();
完整的代码示例：
void MyClass::downloadFile()
    QUrl url("http://example.com/downloadfile.zip");
    QNetworkRequest request(url);
    QNetworkAccessManager* manager = new QNetworkAccessManager(this);
    QNetworkReply* reply = manager->get(request);
    connect(reply, &QNetworkReply::finished, this, &MyClass::downloadFinished);
void MyClass::downloadFinished()
    QNetworkReply* reply = qobject_cast<QNetworkReply*>(sender());
    if(reply)
        if(reply->error() == QNetworkReply::NoError)
            QString fileName = "downloadfile.zip";
            QFile file(fileName);
            if(file.open(QIODevice::WriteOnly))
                file.write(reply->readAll());
                file.close();
        reply->deleteLater();
以上就是在Qt中使用HTTP协议下载文件的方法。