Problem with QThread..

endla.ravi

hi..

I have a widget which is working fyn..

But in background an infinite loop should be there.When i put an infinite loop,the Widget becomes dark and finally crashes..

I think Threads can be used to solve this problem..(correct me if im wrong)

But i am unable to use QThread class ..for example if i have

mainwindow.h
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();

private:
Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H
@

mainwindow.cpp
@
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}

MainWindow::~MainWindow()
{
delete ui;
}
@

main.cpp
@
#include <QtGui/QApplication>
#include "mainwindow.h"

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();

return a.exec&#40;&#41;;

}
@

And a MyThread class like this
@
class MyThread
{
public:void run();

};

void MyThread::run()
{
}
@

Now can anyone explain how to put the widget and while(1) {} loop in two different threads,so that both are running simultaneously...

Thanking u in advance

[edit: Code highlighted / Denis Kormalev]

vcsala

Can you please use '@' tags to make the code more readable?

vcsala

I am not sure you need threads, you can call processEvents from your infinite loop, which makes your GUI items responsive.

DenisKormalev

Please use @ tags for code. I edited your post, but in further posts please use it by yourself.

I don't see any usage of your MyThread class. And it should be inherited from QThread if you want to use threading.

Smar

Usually (mis)using threads causes gui going unresponsive...

Qt already have event loop, using own events and/or signal/slot system.

http://doc.qt.nokia.com/latest/signalsandslots.html
http://doc.qt.nokia.com/latest/eventsandfilters.html

giesbert

endla.ravi what do you want to do in your infinite loop? what is it needed or? Is it background processing (could be done in a thread) or shall it make event processing (is already done by return a.exec();)?

Please specify your needs a bit more.

endla.ravi

@above,

I am actually coding for a messenger

and my client should always be in listen mode,it should be listening for messages from other clients.
But when the client i listening for messages,the client become crashes after some time.

How could i handle this?

giesbert

You can look at the examples: "here":http://doc.qt.nokia.com/4.7/network-network-chat.html

Wolf P.

You have to subclass MyThread from QThread then define in its run method what you want to do in the background. Did you read the "basic thread example":http://doc.qt.nokia.com/4.7/qthread.html#details ?

rugginoso

Maybe in your case it's better to use the QThread::run() default implementation that runs a local (for thread) event loop.
You simply have to create your QWidget and your QThread, than use QObject::moveToThread() method and call the QThread::start() method.

References:
http://labs.qt.nokia.com/2010/06/17/youre-doing-it-wrong/
http://doc.qt.nokia.com/4.7/qthread.html#start
http://doc.qt.nokia.com/4.7/qobject.html#moveToThread

dangelog

[quote]and my client should always be in listen mode,it should be listening for messages from other clients.[/quote]

Please read my article here: http://developer.qt.nokia.com/wiki/ThreadsEventsQObjects . This seems to be the another case where threads are absolutely not needed (and indeed they just make your life a lot harder).

rugginoso

[quote author="peppe" date="1292837082"]
Please read my article here: http://developer.qt.nokia.com/wiki/ThreadsEventsQObjects . This seems to be the another case where threads are absolutely not needed (and indeed they just make your life a lot harder).[/quote]

Really good article :D

Wolf P.

[quote author="Il Rugginoso" date="1292836477"] http://labs.qt.nokia.com/2010/06/17/youre-doing-it-wrong/[/quote] Thanks for the tipp! I didn't know the concepts behind the QThread class...

rugginoso

[quote author="Wolf P." date="1292842687"][quote author="Il Rugginoso" date="1292836477"] http://labs.qt.nokia.com/2010/06/17/youre-doing-it-wrong/[/quote] Thanks for the tipp! I didn't know the concepts behind the QThread class...
[/quote]

You're welcome :D