qt network-programming qt4 qnetworkaccessmanager

QNetworkReply 等待完成

发布于 2024-10-28 05:06:26 字数 456 浏览 8 评论 0原文

我正在使用 Qt 4.6.3 和以下不起作用的代码

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;

，因为该函数返回一个空的 QStringList，应用程序崩溃。如何等到请求完成，然后在一个函数内处理回复

原文

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

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拥有 2024-11-04 05:06:26

您可以使用事件循环：

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

您还应该考虑添加一些比网络超时更短的时间（20 秒？）。即使发生错误，我也不确定是否会调用 finish 。因此，您也有可能连接到错误信号。

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.

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猥︴琐丶欲为 2024-11-04 05:06:26

这里的这些回复都使用旧语法，不适用于最新的QT。

等待网络请求完成：

QEventLoop loop;
connect(reply, &QNetworkReply::finished, &loop, &QEventLoop::quit);
loop.exec();

These replies here are all using old syntax and do not apply to the latest QT.

To wait for the network request to finish:

QEventLoop loop;
connect(reply, &QNetworkReply::finished, &loop, &QEventLoop::quit);
loop.exec();

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弥繁 2024-11-04 05:06:26

首先，我建议您阅读 Qt 文档参考中的相关文档，您可以在这里找到： http ://doc.qt.nokia.com/latest/classes.html。

查看您的代码示例，您似乎已经拥有了 QNetworkRequest 和 QNetworkReply 以及 QNetworkAccessManager。您需要的是将一个槽连接到 finished(QNetworkReply *) 信号。每当待处理的网络回复完成时，就会发出此信号。

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

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

现在，在您的插槽中，您可以读取响应您的请求而发送的数据。像这样的东西：

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

编辑：

要同步等待信号，请使用 QEventLoop。您在这里有一个示例

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

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

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