QNetworkReply wait for finished

问题:

I am using Qt 4.6.3 and the following not-working code

QStringList userInfo;
QNetworkRequest netRequest(QUrl("http://api.stackoverflow.com/1.1/users/587532"));
QNetworkReply *netReply = netman->get(netRequest);

// from here onwards not working
netReply->waitForReadyRead(-1);
if (netReply->isFinished()==true)
{userInfo << do sth to reply;}
return userInfo;

as this function returns an empty QStringList, the app crashes. How to wait until the request has finished and then process the reply within one function

回答1:

You can use event loop:

QEventLoop loop;
connect(netReply, SIGNAL(finished()), &loop, SLOT(quit()));
loop.exec();
// here you have done.

Also you should consider adding some shorter then network timeout (20s?). I'm not sure if finished is called even if an error occured. So it is possible, that you have connect to error signal also.

回答2:

First I recommend you to read the relevant documentation from the Qt Documentation Reference that you can find here: http://doc.qt.nokia.com/latest/classes.html.

Looking at your code sample it seems that you already have, along side with QNetworkRequest and QNetworkReply, a QNetworkAccessManager. What you need is to connect a slot to the finished(QNetworkReply *) signal. This signal is emitted whenever a pending network reply is finished.

QNetworkAccessManager *manager = new QNetworkAccessManager(this);
connect(manager, SIGNAL(finished(QNetworkReply*)),
        this, SLOT(replyFinished(QNetworkReply*)));

manager->get(QNetworkRequest(QUrl("http://api.stackoverflow.com")));

Now, in your slot, you can read the data which was sent in response to your request. Something like:

void MyClass::MySlot(QNetworkReply *data) {
    QFile file("dataFromRequest");
    if (!file.open(QIODevice::WriteOnly))
        return;
    file.write(data->readAll());
    file.close();
}

EDIT:

To wait synchronously for a signal use QEventLoop. You have an example here

http://wiki.forum.nokia.com/index.php/How_to_wait_synchronously_for_a_Signal_in_Qt