QT cpp delay in for loop

Question

i have a loop that fill my textBrowser widget. Now i want to have an 1sec delay in my loop. I want that he append one row and wait 1 sec before fill another row. I tried it with sleep in my loop but it doesnt work. He fill my textbrowser without any delay.

*#include <QThread>*
..
sleep(1);

my code looks like that:

 for(int i = 0; i < array.count(); i++)

   {     
     QString br = "ID-->"+array[i];
     ui->textBrowser->append(br);
   }

How can i delay my loop?

Answer 1

It is best to use events form a QTimer instead of using a loop. For an example, you can use a slot like following.

int i = 0;

void MainWindow::OnTimer()
{
    QString br = "ID-->" + array[i++];
    ui->textBrowser->append(br);
    if (i < array.count())
    {
        QTimer::singleShot(1000, this, SLOT(OnTimer()));
    }
}

You will have to keep array and i as a class variables.

But if you just want to get this done somehow, you can use following code in your loop instead of a sleep. This will block the for loop but continue to process events so the UI will get updated while iterating. But it is kind of a hack.

QEventLoop loop;
QTimer::singleShot(1000, &loop, SLOT(quit()));
loop.exec();