Elapsed Time on a QLabel. How to do it?

[GuangZor]

void MainWindow::updateETLabel(){
        QString text = QTime::currentTime().toString("hh:mm:ss");
	setETLabelText(text);
}
 
//MainWindow constructor:
ETTimer = new QTimer(this);
connect(ETTimer,SIGNAL(timeout()),this,SLOT(updateETLabel()));
 
//StartButton:
ETTimer->start(1000);

void MainWindow::updateETLabel(){
        QString text = QTime::currentTime().toString("hh:mm:ss");
	setETLabelText(text);
}

//MainWindow constructor:
ETTimer = new QTimer(this);
connect(ETTimer,SIGNAL(timeout()),this,SLOT(updateETLabel()));

//StartButton:
ETTimer->start(1000);

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the code above not works of course, because "QTime::currentTime().toString("hh:mm:ss");" only returns the current time...

I wanna make a timer that starts from 00:00:00 and increase each second. But I dont know how to do it in QT. Please I really need your help!

[Lykurg]

Simple use:

QTime t;
t.start();
//...
t.elapsed();

QTime t;
t.start();
//...
t.elapsed();

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=> QTime::elapsed()

[GuangZor]

Thank you for the answer, but how to format the value returned by elapsed() into a "hh:mm:ss" ?
Other question, will I need to use QTimer + QTime together for this task?

[Ginsengelf]

Hi, QTime is enough, you don't need a QTimer. To format the time (it's a millisecond value) just calculate seconds, minutes, etc and build a string from these values.

Ginsengelf

[Lykurg]

QTime is enough. And it returns the seconds so you can calculate the minutes/hours etc yourself using the modulo operator.

EDIT: Ginsengelf was faster and he is right, it returns milliseconds not seconds

[GuangZor]

I dont know how to do it without a QTimer because it not shows the time elapsed every second on a QLabel. Is there any signals for this?
I think think think and I cant reach in any place. Some real code would be appreciated.

Sorry for these very basic questions, but I came from C++BUILDER and using its VCL we do this task very easy using a TTimer component (which executes a callback every second, same as QTimer) and a global "Time" object (which supports arithmetic operations, something like "00:00:00 + 00:00:01" which increases the current time)...

[Lykurg]

Ehm. for clarification: Do you want an analog clock, or do you want an elapsed time? If the second, then yes you have to combine both. QTime to get the elapsed time and a timer for calling the label update.

[ChrisW67]

Something along these lines:

#include <QtGui>
 
class mainwindow: public QMainWindow {
    Q_OBJECT
public:
    mainwindow(QWidget *p = 0): QMainWindow(p) {
        timeLabel = new QLabel(this);
        setCentralWidget(timeLabel);
        time.start();
        updateDisplay();
        connect(&timer, SIGNAL(timeout()), this, SLOT(updateDisplay()));
        timer.start(500);  // twice per second
    }
public slots:
    void updateDisplay() {
        int secs = time.elapsed() / 1000;
        int mins = (secs / 60) % 60;
        int hours = (secs / 3600);
        secs = secs % 60;
        timeLabel->setText(QString("%1:%2:%3")
                            .arg(hours, 2, 10, QLatin1Char('0'))
                            .arg(mins, 2, 10, QLatin1Char('0'))
                            .arg(secs, 2, 10, QLatin1Char('0')) );
    }
private:
    QLabel *timeLabel;
    QTime time;
    QTimer timer;
};
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    mainwindow m;
    m.show();
    return app.exec();
}
#include "main.moc"

#include <QtGui>

class mainwindow: public QMainWindow {
    Q_OBJECT
public:
    mainwindow(QWidget *p = 0): QMainWindow(p) {
        timeLabel = new QLabel(this);
        setCentralWidget(timeLabel);
        time.start();
        updateDisplay();
        connect(&timer, SIGNAL(timeout()), this, SLOT(updateDisplay()));
        timer.start(500);  // twice per second
    }
public slots:
    void updateDisplay() {
        int secs = time.elapsed() / 1000;
        int mins = (secs / 60) % 60;
        int hours = (secs / 3600);
        secs = secs % 60;
        timeLabel->setText(QString("%1:%2:%3")
                            .arg(hours, 2, 10, QLatin1Char('0'))
                            .arg(mins, 2, 10, QLatin1Char('0'))
                            .arg(secs, 2, 10, QLatin1Char('0')) );
    }
private:
    QLabel *timeLabel;
    QTime time;
    QTimer timer;
};

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

    mainwindow m;
    m.show();
    return app.exec();
}
#include "main.moc"

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[Urthas]

I think you might indeed need a QTimer whose timeout() signal is connected to a custom slot that updates the QLabel.

[GuangZor]

Thank you Chrisw67, for the code. Now its clear enough for me. Lykurg, yes I wanted to make an analog clock.

[Lykurg]

Lykurg, yes I wanted to make an analog clock.

Ok, then the elapsed time is useless. There is a good example in the docs. See Digital Clock Example.

[aamer4yu]

Thats digital

Here's Analog example

[selmi.asma]

Thanck you so much ChrisW67,you litterately saved me

[ChrisW67]

You're welcome. Welcome to Qt Centre

[teka321]

maybe better:

MyClass::MyClass(QWidget *parent) :
    QWidget(parent)
{
    QTimer *timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(updateDisplayTime()));
    timer->start(1000);
}
 
 
void MyClass::updateDisplayTime()
{
ui->labelTime->setText(QDateTime::currentDateTime().toString("dddd h:m\ndd.MM.yyyyr.") );
}

MyClass::MyClass(QWidget *parent) :
    QWidget(parent)
{
    QTimer *timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(updateDisplayTime()));
    timer->start(1000);
}


void MyClass::updateDisplayTime()
{
ui->labelTime->setText(QDateTime::currentDateTime().toString("dddd h:m\ndd.MM.yyyyr.") );
}

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