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

Hi everybody,

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

header file:

Code:

---

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();
};

---

src file:

Code:

---

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();
}

---

main file:

Code:

---

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

---

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 ?

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 :

Code:

---

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
}

---

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.

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();
}

---

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.........?

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]