How to make a JPanel selectable

Question

When extending a JPanel and overriding the paintComponent() method the custom JPanel can not be selected so that it gets for example KeyEvents.
But if I make the new Class extend a JButton it gets of course selected and able to receive for example KeyEvents.
My question is therefore; what does the JButton implement that a JPanel doesn’t so that a JButton gets selectable? Or in other words; how to make a JPanel selectable?
Aleksander.

Answer 1

Try this extended code. Only the first panel added can get the Focus.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Test extends JFrame
  public Test()
    setLocation(400,300);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    JPanel panel1 = new JPanel(new BorderLayout());
    JPanel panel2 = new JPanel(new BorderLayout());
    ImagePanel imgPanel = new ImagePanel();
    panel1.setFocusable(true);
    panel2.setFocusable(true);
    panel1.setPreferredSize(new Dimension(0, 50));
    panel2.setPreferredSize(new Dimension(0, 50));
    panel1.setBorder(BorderFactory.createLineBorder(Color.RED,     4));
    panel2.setBorder(BorderFactory.createLineBorder(Color.CYAN,    4));
    imgPanel.setBorder(BorderFactory.createLineBorder(Color.BLACK, 4));
    panel1.add(new JLabel("Panel 1"), BorderLayout.CENTER);
    panel2.add(new JLabel("Panel 2"), BorderLayout.CENTER);
    getContentPane().add(panel1, BorderLayout.NORTH);
    getContentPane().add(panel2, BorderLayout.SOUTH);
    getContentPane().add(imgPanel, BorderLayout.CENTER);   
    pack();
    panel1.addKeyListener(new KeyAdapter(){
        public void keyPressed(KeyEvent ke){
            System.out.println("Panel1");}});
    panel2.addKeyListener(new KeyAdapter(){
        public void keyPressed(KeyEvent ke){
            System.out.println("Panel2");}});
  public static void main(String[] args){new Test().setVisible(true);}
class ImagePanel extends JPanel
  Image img;
  public ImagePanel()
    setFocusable(true);
    setPreferredSize(new Dimension(400,300));
    try{img = javax.imageio.ImageIO.read(new java.net.URL(getClass().getResource("Test.gif"), "Test.gif"));}
    catch(Exception e){/*handled in paintComponent()*/}
    addKeyListener(new KeyAdapter(){
      public void keyPressed(KeyEvent ke){
        System.out.println("ImagePanel");}});
  public void paintComponent(Graphics g)
    if(img != null)
      g.drawImage(img, 0,0,this.getWidth(),this.getHeight(),this);
    else
      g.drawString("This space for rent",50,50);
}