[SOLVED] displaying QSlider value in QDebug() using QThread

bladepopper

I am implementing a simple function where slider value is constantly displayed on label and qDebug(). I already got the label updated using signal/slots, but somehow the qDebug() thread is not working properly. I expected to see the console flooded with the value of the slider. Below is my code:
SliderThread.h:
@class HorizontalSliderThread : public QThread {
Q_OBJECT
public:
HorizontalSliderThread(Ui::MainWindow *ui);//in order to call slider value in HorizontalSliderThread class
~HorizontalSliderThread();
public slots:
void process();
private:
};@
SliderThread.cpp:
@HorizontalSliderThread::HorizontalSliderThread(Ui::MainWindow *ui){
ui_global = *ui;
}
void HorizontalSliderThread::process(){
qDebug("Test Thread");
int value = ui_global.horizontalSlider_windowSize->value();
QObject::connect(ui_global.horizontalSlider_windowSize,SIGNAL(valueChanged(int)),ui_global.label_SliderWindowSize,SLOT(setNum(int)));//update value to label
qDebug()<<value; //update value in console

}@
mainwindow.h move Ui::MainWindow *ui; from private to public.

mainwindow.cpp:
@MainWindow::MainWindow(QWidget parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QThread thread = new QThread;
HorizontalSliderThread* slider = new HorizontalSliderThread(ui);
slider->moveToThread(thread);
connect(thread, SIGNAL(started()), slider, SLOT(process()));
thread->start();
}@

Current Output: qDebug() displays the value of slider once, label is updated constantly.
Expected Output: qDebug() displays the value of slider continuously, label is updated constantly.

Since label is updated when the slider is moved, then the signal/slot for this function is working, which means my thread should be working. Don't know what I'm doing wrong.

QThread implementation is reference from: http://mayaposch.wordpress.com/2011/11/01/how-to-really-truly-use-qthreads-the-full-explanation/

I am fairly new to this, especially QThread, so if there is a better way to implement this function, please let me know!

Thanks a lot.

SOLUTION: change @connect(thread, SIGNAL(started()), slider, SLOT(process()));@
to @connect(ui->horizontalSlider_windowSize,SIGNAL(valueChanged(int)), slider, SLOT(process()));@

dbzhang800

Hi, your QThread make non-sense in your code.

@
MainWindow::MainWindow(QWidget parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QThread thread = new QThread;
HorizontalSliderThread* slider = new HorizontalSliderThread(ui);
connect(thread, SIGNAL(started()), slider, SLOT(process()));
thread->start();
}
@

equals

@
MainWindow::MainWindow(QWidget parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
HorizontalSliderThread slider = new HorizontalSliderThread(ui);
slider.process();
}
@

bladepopper

Hi, I added slider->moveToThread(thread); in the mainwindow.cpp. Hope it clears things up.

Thanks.

dbzhang800

Hi, please note that, QWidget and all of its subclass can only be used in main thread.