How do I draw on a JFrame, or any JComponent?

Question

I am trying to draw something using paint() on my JFrame. I can't get it to show though. Why?

claass DrawOn extends JFrame{
   public static void main(String args[]){
     new DrawOn();
   } 

   public DrawOn(){
     setVisible(true);
     pack();
    }

   paint(Graphics g){
     g.drawOval(10,10,100,100);
   }
}

Answer 1

You should draw in a JPanel :

JPanel panel = new JPanel()
{
    @Override
    protected void paintComponent(Graphics g)
    {
        // TODO Auto-generated method stub
        super.paintComponent(g);
        g.drawOval(10, 10, 100, 100);
    }
};

Don't forget to add the JPanel to the JFrame :

add(panel);

Code:

public DrawOn()
{

    JPanel panel = new JPanel()
    {
        @Override
        protected void paintComponent(Graphics g)
        {
            // TODO Auto-generated method stub
            super.paintComponent(g);
            g.drawOval(10, 10, 100, 100);
        }
    };

    add(panel);
    setPreferredSize(new Dimension(200, 200));
    setVisible(true);
    pack();
}

Note: You could make a class that extends JPanel instead of using an anonymous class so your code is clearer.