Delay produce in qt C++ for qt 4.8.7

[Mijaz]

I want to produce delay in my code for 500ms. I have tried following commands.
1). QThread::msleep(500);
2). delay(500);
3). sleep(500);

command (1). produce delay but when I deploy the project to my SDR board it pops error that "QThread cannot yous in this scope" because my board running qt4.8.7 not the latest. So I used 2). and 3). but they are not working.
Please guide me how I can produce a delay for qt4.8.7 version.

[jsulm]

@Mijaz It is already supported in Qt4: https://doc.qt.io/archives/qt-4.8/qthread.html#msleep
When and where do you get that error?

[JKSH]

@jsulm said in Dealy produce in qt C++ for qt 4.8.7:

It is already supported in Qt4: https://doc.qt.io/archives/qt-4.8/qthread.html#msleep

QThread::msleep() is public in Qt 5 but protected in Qt 4. So, Qt 4, QThread::msleep() must be called by a QThread subclass.

[jsulm]

@JKSH Oh, you're right it's early morning here :-)

[aha_1980]

@Mijaz all the calls you mentioned are blocking. The better way is to use a QTimer and connect a slot to the timeout() signal.

Regards

[Mijaz]

@aha_1980
I tried to use QTimer but I don't understand, how it will use for my purpose.
Will you please help me to write a simple widget program in which when I click a pushButton1 the LineEdit start blink and when click pushButton2 LineEdit stops blink.

[jsulm]

@Mijaz You have it here: https://forum.qt.io/topic/65799/how-to-display-label-for-30-seconds-and-then-hide-it/30
There is really nothing special to it:

QTimer *timer = new QTimer(this);
connect(timer, &QTimer::timeout, this, &MainWindow::toggleLineEdit);
timer->start(1000);

void MainWindow::toggleLineEdit()
{
    ui->lineEdit->setChecked(!ui->lineEdit->checked());
   ...
}

Your both buttons then simply start the timer or stop it.

[Pradeep P N]

Hi @Mijaz

You can also use QEventLoop check below methods from documentation.

• exec() : Enters the main event loop and waits until exit() is called. Returns the value that was passed to exit().
• exit() : Tells the event loop to exit with a return code.

Hope this may help you.
All the best.