How do I create a pause/wait function using Qt?

Question

I\'m playing around with Qt, and I want to create a simple pause between two commands. However it won\'t seem to let me use Sleep(int mili);, and I can\'t find

Answer 1

If you want a cross-platform method of doing this, the general pattern is to derive from QThread and create a function (static, if you'd like) in your derived class that will call one of the sleep functions in QThread.

Answer 2

Similar to some answers here, but maybe a little more lightweight

void MyClass::sleepFor(qint64 milliseconds){
    qint64 timeToExitFunction = QDateTime::currentMSecsSinceEpoch()+milliseconds;
    while(timeToExitFunction>QDateTime::currentMSecsSinceEpoch()){
        QApplication::processEvents(QEventLoop::AllEvents, 100);
    }
}

Answer 3

Small +1 to kshark27's answer to make it dynamic:

#include <QTime>

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

Answer 4

To use the standard sleep function add the following in your .cpp file:

#include <unistd.h>

As of Qt version 4.8, the following sleep functions are available:

void QThread::msleep(unsigned long msecs)
void QThread::sleep(unsigned long secs)
void QThread::usleep(unsigned long usecs)

To use them, simply add the following in your .cpp file:

#include <QThread>

Reference: QThread (via Qt documentation): http://doc.qt.io/qt-4.8/qthread.html

Otherwise, perform these steps...

Modify the project file as follows:

CONFIG += qtestlib

Note that in newer versions of Qt you will get the following error:

Project WARNING: CONFIG+=qtestlib is deprecated. Use QT+=testlib instead.

... so, instead modify the project file as follows:

QT += testlib

Then, in your .cpp file, be sure to add the following:

#include <QtTest>

And then use one of the sleep functions like so:

usleep(100);

Answer 5

I wrote a super simple delay function for an application I developed in Qt.

I would advise you to use this code rather than the sleep function as it won't let your GUI freeze.

Here is the code:

void delay()
{
    QTime dieTime= QTime::currentTime().addSecs(1);
    while (QTime::currentTime() < dieTime)
        QCoreApplication::processEvents(QEventLoop::AllEvents, 100);
}

To delay an event by n seconds - use addSecs(n).

Answer 6

we can use following method QT_Delay:

QTimer::singleShot(2000,this,SLOT(print_lcd()));

This will wait for 2 seconds before calling print_lcd().