QThread signal and slots problem

[mero]

Hello,
I don't know why slot is not working...

k.h

class logoThread : public QThread
{
    Q_OBJECT
public:
    logoThread(QString param1, QString param2) { strUrl = param1; QString strChannel = param2;  }
 
    void run()
    {
        QTimer::singleShot(0, this, SLOT(doTheWork()));
 
        exec();
    }
 
public slots:
    void doTheWork()
    {
        QNetworkAccessManager accessManager;
        QNetworkReply* pReply;
        QEventLoop eventLoop;
        pReply = accessManager.get(QNetworkRequest(QUrl(strUrl)));
        QObject::connect(pReply, SIGNAL(finished()), &eventLoop, SLOT(quit()));
        eventLoop.exec();
 
        QByteArray bData = pReply->readAll();
 
        delete pReply;
qDebug() << "got img";
        emit setLogo(strChannel, bData);
 
        quit(); // not needed ?
    }
 
private:
    QString strUrl;
    QString strChannel;
 
signals:
    void setLogo(QString, QByteArray);
 
};
 
class k : public QObject
{
    Q_OBJECT
public:
...
 
public slots:
    void setLogoS(QString, QByteArray);
}

class logoThread : public QThread
{
    Q_OBJECT
public:
    logoThread(QString param1, QString param2) { strUrl = param1; QString strChannel = param2;  }

    void run()
    {
        QTimer::singleShot(0, this, SLOT(doTheWork()));

        exec();
    }

public slots:
    void doTheWork()
    {
        QNetworkAccessManager accessManager;
        QNetworkReply* pReply;
        QEventLoop eventLoop;
        pReply = accessManager.get(QNetworkRequest(QUrl(strUrl)));
        QObject::connect(pReply, SIGNAL(finished()), &eventLoop, SLOT(quit()));
        eventLoop.exec();

        QByteArray bData = pReply->readAll();

        delete pReply;
qDebug() << "got img";
        emit setLogo(strChannel, bData);

        quit(); // not needed ?
    }

private:
    QString strUrl;
    QString strChannel;

signals:
    void setLogo(QString, QByteArray);

};

class k : public QObject
{
    Q_OBJECT
public:
...

public slots:
    void setLogoS(QString, QByteArray);
}

To copy to clipboard, switch view to plain text mode 

k.cpp

void k::img()
{
....
                logoThread *logoThr = new logoThread(strU, strC);
                QObject::connect(logoThr, SIGNAL(setLogo(QString,QByteArray)), this, SLOT(setLogoS(QString,QByteArray)), Qt::QueuedConnection);
                logoThr->start();
            }
        }
    }
}
 
void k::setLogoS(QString param1, QByteArray param2)
{
    qDebug() << "slot";
// show img
}

void k::img()
{
....
                logoThread *logoThr = new logoThread(strU, strC);
                QObject::connect(logoThr, SIGNAL(setLogo(QString,QByteArray)), this, SLOT(setLogoS(QString,QByteArray)), Qt::QueuedConnection);
                logoThr->start();
            }
        }
    }
}

void k::setLogoS(QString param1, QByteArray param2)
{
    qDebug() << "slot";
// show img
}

To copy to clipboard, switch view to plain text mode 

[Lykurg]

I guess the slot is called, but you don't receive any data. That's because get() works asynchronously! Read on how to use QNetworkAccessManager correctly. (Your posted thread class looks also very very crowded and "ugly"!)

[mero]

I recieve data, but slot is not called.

[Lykurg]

I used your code (only removed the network things):

#include <QtGui>
 
 
 
class logoThread : public QThread
{
    Q_OBJECT
 
  public:
    logoThread(QString param1, QString param2)
    {
      strUrl = param1;
      strChannel = param2;
    }
 
    void run()
    {
      QTimer::singleShot(0, this, SLOT(doTheWork()));
      exec();
    }
 
  public slots:
    void doTheWork()
    {
      qDebug() << "got img";
      QByteArray bData;
      emit setLogo(strChannel, bData);
      quit(); // not needed ?
    }
 
  private:
    QString strUrl;
    QString strChannel;
 
  signals:
    void setLogo(QString, QByteArray);
};
 
class k : public QObject
{
    Q_OBJECT
  public:
    k(QObject* parent = 0) : QObject(parent) {}
 
  public slots:
    void setLogoS(QString, QByteArray)
    {
      qDebug() << __FUNCTION__ << "reached";
    }
};
 
int main(int argc, char** argv)
{
  QApplication app(argc, argv);
 
  k test;
  logoThread* logoThr = new logoThread("foo", "bar");
  QObject::connect(logoThr, SIGNAL(setLogo(QString, QByteArray)), &test, SLOT(setLogoS(QString, QByteArray)), Qt::QueuedConnection);
  logoThr->start();
 
  return app.exec();
}
 
 
#include "main.moc"

#include <QtGui>



class logoThread : public QThread
{
    Q_OBJECT

  public:
    logoThread(QString param1, QString param2)
    {
      strUrl = param1;
      strChannel = param2;
    }

    void run()
    {
      QTimer::singleShot(0, this, SLOT(doTheWork()));
      exec();
    }

  public slots:
    void doTheWork()
    {
      qDebug() << "got img";
      QByteArray bData;
      emit setLogo(strChannel, bData);
      quit(); // not needed ?
    }

  private:
    QString strUrl;
    QString strChannel;

  signals:
    void setLogo(QString, QByteArray);
};

class k : public QObject
{
    Q_OBJECT
  public:
    k(QObject* parent = 0) : QObject(parent) {}

  public slots:
    void setLogoS(QString, QByteArray)
    {
      qDebug() << __FUNCTION__ << "reached";
    }
};

int main(int argc, char** argv)
{
  QApplication app(argc, argv);

  k test;
  logoThread* logoThr = new logoThread("foo", "bar");
  QObject::connect(logoThr, SIGNAL(setLogo(QString, QByteArray)), &test, SLOT(setLogoS(QString, QByteArray)), Qt::QueuedConnection);
  logoThr->start();

  return app.exec();
}


#include "main.moc"

To copy to clipboard, switch view to plain text mode 

and the slot is called! So the error must be somewhere else in your original code. Try to strip your code down to locate the error.

[wysota]

The slot will be called in context of the main thread, not the thread represented by the QThread object which is probably not what you want as your thread is otherwise idle. If you main thread is blocked, the slot will not be called.

[Zmrca]

The slot will be called in context of the main thread, not the thread represented by the QThread object which is probably not what you want as your thread is otherwise idle. If you main thread is blocked, the slot will not be called.

I agree with what wysota said. I met the same proble with using a thread to connect with Http server. And slots are called ,but reply->readAll() return empty. That issues makes me almost crazy.
Finally, I rethink about if thread really send out request.
I think NetworkAccessManager just put data and request into a queue which only main thread can send it out. So I recommand you use a QTimer in your class logoThread instead of thread ,and if so, the request can been sent and datas can be read correctly.I did so , and got datas from Http server. I think that may help you.

[squidge]

Have you looked at the documentation for moveToThread?

[mero]

Have you looked at the documentation for moveToThread?

yes, but I don't know where use it ;/

[mero]

I used your code (only removed the network things): and the slot is called! So the error must be somewhere else in your original code. Try to strip your code down to locate the error.

Thank you - Yes, error was somewhere else in code.