Displaying a live timer in a window

[aemara]

Hi guys

I've been trying to use QTcreator to display a timer in a dialog or window. I start the timer, then use a delay function, then measure the time elapsed. My goal is to continuously display the time elapsed onto the window, as if I had a live timer, but it seems that every time I output the time elapsed to the window, it only outputs the final time ie if I use a delay of 5 seconds, then my window takes 5 seconds to open, then it displays 5 seconds; when in fact i want the window to open instantly and diplay 1,2,3,4,5.

Here's what I have so far:

void delay()
{
   QTime dieTime= QTime::currentTime().addSecs(3);
   while( QTime::currentTime() < dieTime )
   QCoreApplication::processEvents(QEventLoop::AllEvents, 100);
}
 
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
     ui->setupUi(this);
     QElapsedTimer timer;
     timer.start();
     delay();
     connect(timer.elapsed(),SIGNAL(valueChange(int)), ui->progressBar,SLOT(setValue(int)));  // but apparently timer.elapsed doesn't work as a const QObject

void delay()
{
   QTime dieTime= QTime::currentTime().addSecs(3);
   while( QTime::currentTime() < dieTime )
   QCoreApplication::processEvents(QEventLoop::AllEvents, 100);
}


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
     ui->setupUi(this);
     QElapsedTimer timer;
     timer.start();
     delay();
     connect(timer.elapsed(),SIGNAL(valueChange(int)), ui->progressBar,SLOT(setValue(int)));  // but apparently timer.elapsed doesn't work as a const QObject

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Then I tried another approach

for (int i=1; i<=3000; i++)
        while (!timer.hasExpired(3000))
    {
       ui->lineEdit->setText(QString::number(timer.elapsed())); // trying to display timer in line edit
       ui->progressBar->setValue(timer.elapsed()/30);             // trying to use a progress bar to track the time
    }

for (int i=1; i<=3000; i++)
        while (!timer.hasExpired(3000))
    {
       ui->lineEdit->setText(QString::number(timer.elapsed())); // trying to display timer in line edit
       ui->progressBar->setValue(timer.elapsed()/30);             // trying to use a progress bar to track the time
    }

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Does anyone have good pointers to help me solve this?

Thanks in advance

-Emara

[boudie]

Create a QTimer.
Connect the timeout() signal to a slot.
Set interval.
Start the timer.
Have fun.

[aemara]

I've tried that now, but now it doesn't even update the time. I changed the Second "this" to ui->progressBar, and the progress bar just shows me 24.
Do you mind expanding your answer a little bit more? I just started using QT last week so I might be doing something else wrong.

Thank you for your reply.

[boudie]

Start reading this:
http://qt-project.org/doc/qt-4.8/qtimer.html

I don't think a QElapsedTimer is the right class to use, but I might be misunderstanding your goal...

[ChrisW67]

Use QTime::start() to start recording elapsed time on a QTime object. Use QTimer (or some other mechanism) to periodically fire a slot and update a display with the current QTime::elapsed() time from the QTime object. No loops, no processEvents() calls.