[Qt concurrent] Emit signal from run method do not work

[vishwajeet.dusane]

Hi Guys,

I have test() function which is executed using QtConcurrent::run method in different thread. My main thread is GUI thread. When any signal is emmited from test() function, main thread does not catch that so i tried to execute slot OnTestSignal() which executes in main thread and emit signal from there. still the signal is not emmited.

For more detail i have documented code.

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QtConcurrentRun>
#include <QCoreApplication>
#include <QTimer>

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

    // Run test in different thread
   QtConcurrent::run((*this),&MainWindow::test);

    QObject::connect(this,SIGNAL(testSignal(int)),ui->progressBar,SLOT(setValue(int)),Qt::QueuedConnection);

    /**
      * This signal is emmited and progress bar changes
      */
    emit testSignal(qrand()%100);
}

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

void MainWindow::test()
{
    qDebug() << "start :" << QThread::currentThread() ->signalsBlocked()<< " : " << thread()->signalsBlocked();
    qDebug() << "Thread : " << QThread::currentThread() << " : " << thread();

    int i;
    int j;
    while(1) {
        ++i;

        if(i > 10) {
            i =0;
            QMetaObject::invokeMethod(this,"onTestSignal",Qt::QueuedConnection);
            //emit testSignal(); /* DOES NOT WORK */

        }
    }

}

void MainWindow::onTestSignal()
{
    // Verify that test executed in different thread and this funtion is executed in main thread

    qDebug() << "onTestSignal() : " << QThread::currentThread() << " :Main Thread : " << thread();

    /**
      * Executed in main thread still signal is not been emmited, WHY ????
      */
    emit testSignal(qrand()%100);

    // Did not work
    QCoreApplication::processEvents();
}

What am i doing wrong here ? i should be getting a signal but that not happening

haws anybody faced similar issue?

[rahulvala]

#include <QtGui/QApplication>

[vishwajeet.dusane]

#include <QtGui/QApplication>

Do you actually have any suggestion on this ?

[rahulvala]

What error or warning are you getting exactly ?

[gnuton]

Hi,
Does it run test()? If yes.. I'm surprised! And I'm surprised you don't get any error message in the console!
I cannot really understand how QtConcourent could run in a different thread a class method.
MAYBE QtCuncurrent could accept static const class methods... but for sure it cannot run your a standard yourclass::test() method,
because the class object is instanced in a different thread.