[Solved] How to connect() between wizardpage and thread

roseicollis

Hi!

I am making a GUI app with wizard structure and I have:

the main.cpp
the class MainWindow : public QMainWindow basic class
class BaseWizard : public QWizard
class BasePage : public QWizardPage
all the pages(wp1, wp2, wp3 ...) like this: class WP1 : public BasePage

And finally a thread to be able to do some background work when needed:

class WorkThread : public QThread

So what I need is: In wp2 and wp6 for example, I need to do some background work so I suppose that I have to emit a signal which has to be connected to the workthread slot which does the work... I've do that but seems that there is something wrong with the connection:

@
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
BaseWizard wizard; //this starts the app

//this is for the connection between basepage and workthread
BasePage bp;
WorkThread mt;
bp.conexion(&mt);
mt.start();

wizard.show();
return app.exec&#40;&#41;;

}
@

@
void BasePage::conexion(WorkThread *mt)
{
connect(this, SIGNAL(swp2()), mt, SLOT(recwp2()));
}

void BasePage::SendSignal()
{
emit(swp2());
}
@

@
void WorkThread::recwp2()
{
qDebug() << "hi";
//do things
}
@

and then in wp2 where I want to do the background work:
@
BasePage::SendSignal();
@

I have debugged it and when the program arrives to the emit, then nothing happens. I know that the workthread is running well because if I do this, it prints the message:

@
void WorkThread::run()
{
exec();
}

void WorkThread::exec()
{
recwp2();
}@

Thank you so much!

ckakman

Hi,

In your case, you don't need to derive your Worker class from QThread. Derive it from QObject and move it to a QThread instance. Assuming that you derived your Worker object from QObject:
@
// in the UI thread
QThread workerThread = new QThread(this);
Worker *worker = new Worker; //Don't set a parent
worker->moveToThread( workerThread );
workerThread->start();

// keep a pointer to Worker somewhere
// make connections between wizard pages and Worker object.

...

//in the destructor
QThread *wt = worker->thread();
worker->deleteLater();

wt->quit();
wt->wait();
@

You may "this page":http://doc.qt.io/qt-5/threads-technologies.html#choosing-an-appropriate-approach useful.

In your code, you seem to have reimplemented exec(). QThread::exec() runs an event loop so that the signals-slot mechanism works. You have properly rendered QThread useless by reimplementing that function. I'd suggest that you shouldn't derive from QThread until you consider yourself quite experienced with threads.

SGaist

Hi,

To add to ckakman, you are doing your connection on a page that you never show, nor put in your wizard

roseicollis

Hi,

Yeah, that works for my problem :D

Thank you!