JPanel not calling paintComponent in java

Question

I have worked on this for hours upon hours and it doesn't work. I want to have a pixel appear on the screen, but the paint component doesn't work I don't understand why. The setupFrame method is called from the main method.

public static void setupFrame()
{
 JFrame frame = new JFrame("graphicsTest");
 JPanel panel = new JPanel();
 panel.setBounds(0, 0, 1080, 1080/2);
 frame.add(panel);
 frame.pack();
 frame.setSize(1080, 1080/2);
 frame.setVisible(true);
 frame.setResizable(false);
 frame.repaint();
}
@Override
public void paintComponent(Graphics g) {
 g.fillRect(0, 0, 50, 50);
} 

• Andrew Thompson: For better help sooner, edit to add a minimal reproducible example or Short, Self Contained, Correct Example.

Answer 1

You're overloading the paintComponent() in the class you've created (let's call it MyPanel) but you're creating an instance of another class:

JPanel panel = new JPanel();

So there's no instance of MyPanel here and the method is not called. You need to use the class where you've overloaded the paintComponent method:

MyPanel panel = new MyPanel();

Or (this should be equivalent):

JPanel panel = new MyPanel();