paintEvent problem

Dear Experts!!
I have a problem with my painter. I want to paint my form by without using paint event.
Is it possible? In some examples I saw that they use QPixmap for painting on it. Is it a good way to paint on a pixmap and locate it on my form?

Thanks

Code:

pixmap = QPixmap(100, 100);
         pixmap.fill(Qt::transparent);
 
         QRadialGradient gradient(50, 50, 50, 50, 50);
         gradient.setColorAt(0, QColor::fromRgbF(1, 0, 0, 1));
         gradient.setColorAt(1, QColor::fromRgbF(0, 0, 0, 0));
         QPainter painter(&pixmap);
         painter.fillRect(0, 0, 100, 100, gradient);
 
         channelImage = pixmap.alphaChannel();
         update();