Code fails to paint on first click, works well on subsequent click.

Question

This code runs when I click a button:
        Graphics g = jPanel3.getGraphics();
        g.drawImage(i, 0, 0, Iob);The first time I click this button after program load, the image half flashes up where it's supposed to go, then reverts to the original background color.
Every time after that, I click and it draws the image stored in i onto jPanel3, which is what I want, but I'm stumped on why this doesn't work on the first click.
Thanks in advance.
Hans.

Answer 1

using something like
                jPanel3.paintComponents(g);or
                jPanel3.paint(g);
I don't understand how this works.
I have to make a Graphics variable g equal to something in order to initialize it and use it, why can't i make it equal to the graphics of the component I want to paint?
people keep telling me not to use getGraphics().
what should i use then?
Graphics g = ????????:if i use null, i get exceptions, what do I make it equal to if not component.getGraphics?