My QTimer is not starting in another slot/function, but it's startin from constructor

[sanjeet]

Hi everybody,

I am having one problem, i am giving you code can you find out where is problem.

header file:

class MainDialog : public QDialog
{
                Q_OBJECT
        public:
                MainDialog();
        private:
                QLabel* labelText;
                QLabel* labelImage;
                QTimer *timer;
                QPushButton* startButton;
                QPushButton* quitButton;
                QSpacerItem* vspacer;
 
                QStringList imagesStrList;
                int count;
                int listSize;
        private slots:
                void updateImages();
                void animateImage();
};

class MainDialog : public QDialog
{
                Q_OBJECT
        public:
                MainDialog();
        private:
                QLabel* labelText;
                QLabel* labelImage;
                QTimer *timer;
                QPushButton* startButton;
                QPushButton* quitButton;
                QSpacerItem* vspacer;

                QStringList imagesStrList;
                int count;
                int listSize;
        private slots:
                void updateImages();
                void animateImage();
};

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src file:

MainDialog::MainDialog() : QDialog()
{
        QVBoxLayout *mainLayout = new QVBoxLayout(this);
        QHBoxLayout *hLayout = new QHBoxLayout;
 
        labelText = new QLabel;
        labelText->setText("My Dialog ... !");
 
        labelImage = new QLabel;
 
        vspacer = new QSpacerItem(20, 150, QSizePolicy::Expanding, QSizePolicy::Minimum);
 
        startButton = new QPushButton("Start");
        quitButton = new QPushButton("Quit");
 
        hLayout->addWidget(startButton);
        hLayout->addWidget(quitButton);
 
        mainLayout->addWidget(labelText);
        mainLayout->addItem(vspacer);
        mainLayout->addLayout(hLayout);
 
        timer = new QTimer;
        imagesStrList << ":/images/1.png"
                      << ":/images/2.png"
                      << ":/images/3.png"
                      << ":/images/4.png"
                      << ":/images/5.png"
                      << ":/images/6.png";
 
                count = 0;
                listSize = imagesStrList.size();
 
        connect(timer, SIGNAL(timeout()),this, SLOT(updateImages()));
        connect(startButton, SIGNAL(clicked()),this, SLOT(animateImage()));
        connect(quitButton, SIGNAL(clicked()),this, SLOT(close()));
 
        //timer->start(400); //[COLOR="#0000FF"] it's working[/COLOR]
 
        resize(320,240);
 
}
 
void MainDialog::updateImages()
{
                qDebug("update");
          labelImage->setPixmap(QPixmap(imagesStrList.at(count++)));
          labelImage->show();
 
          if(count>=listSize){
                count=0;
          }
 
}
 
void MainDialog::animateImage()
{
        timer->start(400); //[COLOR="#FF0000"] It's not calling timer slot, I have to srart timer in this slot[/COLOR]
        for(int i=0; i<10; i++){
                qDebug("LOOP : %d",i);
                sleep(1);
        }
        timer->stop();
}

MainDialog::MainDialog() : QDialog()
{
        QVBoxLayout *mainLayout = new QVBoxLayout(this);
        QHBoxLayout *hLayout = new QHBoxLayout;

        labelText = new QLabel;
        labelText->setText("My Dialog ... !");

        labelImage = new QLabel;

        vspacer = new QSpacerItem(20, 150, QSizePolicy::Expanding, QSizePolicy::Minimum);

        startButton = new QPushButton("Start");
        quitButton = new QPushButton("Quit");

        hLayout->addWidget(startButton);
        hLayout->addWidget(quitButton);

        mainLayout->addWidget(labelText);
        mainLayout->addItem(vspacer);
        mainLayout->addLayout(hLayout);

        timer = new QTimer;
        imagesStrList << ":/images/1.png"
                      << ":/images/2.png"
                      << ":/images/3.png"
                      << ":/images/4.png"
                      << ":/images/5.png"
                      << ":/images/6.png";

                count = 0;
                listSize = imagesStrList.size();

        connect(timer, SIGNAL(timeout()),this, SLOT(updateImages()));
        connect(startButton, SIGNAL(clicked()),this, SLOT(animateImage()));
        connect(quitButton, SIGNAL(clicked()),this, SLOT(close()));

        //timer->start(400); //[COLOR="#0000FF"] it's working[/COLOR]

        resize(320,240);

}

void MainDialog::updateImages()
{
                qDebug("update");
          labelImage->setPixmap(QPixmap(imagesStrList.at(count++)));
          labelImage->show();

          if(count>=listSize){
                count=0;
          }

}

void MainDialog::animateImage()
{
        timer->start(400); //[COLOR="#FF0000"] It's not calling timer slot, I have to srart timer in this slot[/COLOR]
        for(int i=0; i<10; i++){
                qDebug("LOOP : %d",i);
                sleep(1);
        }
        timer->stop();
}

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main file:

int main(int argc, char *argv[])
{
        QApplication a(argc, argv);
 
        Q_INIT_RESOURCE(resource);
 
        MainDialog dlg;
        dlg.show();
 
return a.exec();
}

int main(int argc, char *argv[])
{
        QApplication a(argc, argv);

        Q_INIT_RESOURCE(resource);

        MainDialog dlg;
        dlg.show();

return a.exec();
}

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i have to start my timer in different slot, but it's not calling the timer slot, if i am starting the timer in constructor, it's working fine.
can you tel me where i am doing wrong ?

[Lesiok]

Because for loop in animateImage() method is blocking application event loop.
If you want to do animation for a while you have to use second QTimer to stop it. Something like this :

void MainDialog::animateImage()
{
        timer->start(400); //[COLOR="#FF0000"] It's not calling timer slot, I have to srart timer in this slot[/COLOR]
        QTimer::singleShot(10000,timer,SLOT(stop()));//stop animation after 10 seconds
}

void MainDialog::animateImage()
{
        timer->start(400); //[COLOR="#FF0000"] It's not calling timer slot, I have to srart timer in this slot[/COLOR]
        QTimer::singleShot(10000,timer,SLOT(stop()));//stop animation after 10 seconds
}

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[sanjeet]

hi Lesiok,
first of all thanks for suggesting me.
But my problem is, i have to exeucute some busy process there, i dont know how much time exactly it will take to finish.
So, i cant take second timer as single shot.
I am writing down again that part of code.

void MainDialog::animateImage()
{
 timer->start(400); // It's not calling timer slot, I have to srart timer in this slot
 
 some_busy_or_long_process();  // i dont know how much time it will take, may be 10 sec, 5 sec, 12 sec etc,
 
 timer->stop();
}

void MainDialog::animateImage()
{
 timer->start(400); // It's not calling timer slot, I have to srart timer in this slot

 some_busy_or_long_process();  // i dont know how much time it will take, may be 10 sec, 5 sec, 12 sec etc,

 timer->stop();
}

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I have to start timer before execution of that busy process and i have to stop it after finishing that busy process.
can you give me some idea.........?

[ChrisW67]

Your program cannot service the timeout() signal unless your code returns to the event loop.

You should read this: [wiki=Keeping_the_GUI_Responsive]Keeping the GUI Responsive[/wiki]