qt - Qt下的HTTP GET

Question

我有一个 n00b 问题，我似乎无法从我的 Qt 代码发出 HTTP GET 请求...

这里是应该工作的代码:

void MainWindow::requestShowPage(){
    QNetworkAccessManager *manager = new QNetworkAccessManager(this);
    connect(manager,SIGNAL(finished(QNetworkReply*)),this,SLOT(requestReceived(QNetworkReply*)));
manager->get(QNetworkRequest(QUrl("http://google.com")));
}

void MainWindow::requestReceived(QNetworkReply* reply){
    QString replyText;
    replyText.fromAscii(reply->readAll());

    ui->txt_debug->appendPlainText(replyText);
}

但问题是这不起作用:在 requestReceived(QNetworkReply* reply) 中，replyText 似乎是空的，reply->error() 返回 0 并且 reply->errorString() 返回“未知错误”。我真的不知道现在该怎么办...

有什么想法吗？

Answer 1

明显有重定向，不认为是错误。
您应该使用回复属性中提供的重定向 url 运行新请求，直到获得真实页面:

void MainWindow::requestReceived(QNetworkReply *reply)
{
    reply->deleteLater();

    if(reply->error() == QNetworkReply::NoError) {
        // Get the http status code
        int v = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
        if (v >= 200 && v < 300) // Success
        {
             // Here we got the final reply 
            QString replyText = reply->readAll();
            ui->txt_debug->appendPlainText(replyText);
        } 
        else if (v >= 300 && v < 400) // Redirection
        {
            // Get the redirection url
            QUrl newUrl = reply->attribute(QNetworkRequest::RedirectionTargetAttribute).toUrl();
            // Because the redirection url can be relative, 
            // we have to use the previous one to resolve it 
            newUrl = reply->url().resolved(newUrl);

            QNetworkAccessManager *manager = reply->manager();
            QNetworkRequest redirection(newUrl);
            QNetworkReply *newReply = manager->get(redirection);

            return; // to keep the manager for the next request
        } 
    } 
    else 
    {
        // Error
        ui->txt_debug->appendPlainText(reply->errorString());
    }

    reply->manager()->deleteLater();
}

您还应该记录重定向的位置或计算重定向的次数，以避免永无止境的循环。