QScreen size returning zero

[alistair]

Hi,

I am using the following function to return screen size:

QScreen *screen = QApplication::screens().at(0);
    screenWidth = screen->availableSize().width();
    screenHeight = screen->availableSize().height();

QScreen *screen = QApplication::screens().at(0);
    screenWidth = screen->availableSize().width();
    screenHeight = screen->availableSize().height();

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I tested this code by making a push button and on the button click, it runs this code and it works. Although when I try putting this code in my constructor function, it keeps returning screenWidth = 0 and screenHeight = 0.

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    QScreen *screen = QApplication::screens().at(0);
    screenWidth = screen->availableSize().width();
    screenHeight = screen->availableSize().height();
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QScreen *screen = QApplication::screens().at(0);
    screenWidth = screen->availableSize().width();
    screenHeight = screen->availableSize().height();
}

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Any help would be greatly appreciated, thank you .