在Qt下进行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,这只是不起作用:在requestReceived(QNetworkReply* reply),replyText似乎是空的,reply->error()返回0并reply->errorString()返回"未知错误".我现在真的不知道该怎么办......

任何的想法？

Answer 1

显然有重定向,不被视为错误.
您应该使用回复属性中提供的重定向URL运行新请求,直到获得真实页面为止:

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();
}

您还应记录重定向的位置或计算重定向的数量,以避免永不结束的循环.