Image only shows after screen is reloaded (hidden and showed again)

Question

Hello everyone,
I have a class that calls a drawImage. The thing is that it was supposed to be shown when the JFrame is shown, but it isn't. It is only shown after I hide it and show it again (like after I minimize it and minimize it back.
Can anyone help me here? I need it loading without nothing being done by the user.
Here goes my class:
import java.awt.*;
import javax.swing.*;
import java.awt.geom.*;
import java.awt.image.*;
import java.applet.*;
import sun.audio.*;
import java.io.*;
public class Shapes extends JFrame
    public Image imagem;
    public Shapes(Integer resultado, Image imagem)
        super("Grafico dos Valores");
        setBounds( 0, 0, 900, 570 );
        getContentPane().setLayout(null);
        this.imagem = imagem;
        setVisible(true);
        getGraphics().drawImage(imagem, 20, 20, null);   
    public void paint(Graphics g)
        super.paint(g);
        Graphics2D g2d = ( Graphics2D ) g;
        g2d.drawImage(imagem, 20, 20, null);   
    }

Answer 1

1) Swing related questions should be posted in the Swing forum
2) Don't override the paint(...) method of JFrame
3) Don't use getGraphics to draw your image
4) If you need to do custom painting then override paintComponent(..) of JPanel or JComponent
5) Read the tutorial on [url http://java.sun.com/docs/books/tutorial/uiswing/14painting/index.html]Custom Painting