Ajouter des boutons pour un JDialog?

Je suis en train de faire un JButton sur un JDialog, mais, le bouton de couvrir l'ensemble de la JDialog, toute aide à ce sujet? C'est à quoi il ressemble:

C'est comment j'ai créer le JDialog et la JButton:

class MenuStoreHandler implements ActionListener{
    public void actionPerformed(ActionEvent e){

        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        int screenWidth = (int) dim.getWidth();
        int screenHeight = (int) dim.getHeight();

        JDialog g = new JDialog();
        g.setTitle("The Store");
        g.setSize(200, 200);
        g.setLocation(screenWidth / 2 - 150, screenHeight / 2 - 150);

        JButton b = new JButton("Buy");
        b.addActionListener( new StoreItem1Handler() );
        b.setVisible(true);
        g.add(b);

        g.setVisible(true);
    }
}

Je vais juste poster mon plein MrStan.class, elle est ici:

package Progress;
public class MrStan extends JPanel{
private Timer timer = new Timer();
public static int points;
static File h = new File("text.txt");
public ImageIcon bg = new ImageIcon("D:/MrStan/bg.png");
static JMenuBar menubar;
Formatter x;
JMenu menu;
JMenuItem menuitem;
double version = 0.3;
class todoTask extends TimerTask{
public void run(){ 
points += 1;
repaint();
}
}
public int getPoints(){
return points;
}
public void setPoints( int points ){
this.points = points;
}
public MrStan(){
setIgnoreRepaint(true);
menubar = new JMenuBar();
menu = new JMenu("Menu");
menu.setMnemonic(KeyEvent.VK_F);
menu.getAccessibleContext().setAccessibleDescription("Menu");
menubar.add(menu);
menuitem = new JMenuItem("Store (S)", new ImageIcon("coins.png"));
menuitem.setMnemonic(KeyEvent.VK_S);
menuitem.addActionListener( new MenuStoreHandler() );
menu.add(menuitem);
menuitem = new JMenuItem("Reset Points (R)", new ImageIcon("delete.png"));
menuitem.setMnemonic(KeyEvent.VK_R);
menuitem.addActionListener( new MenuResetPointHandler() );
menu.add(menuitem);
//add a separator
menu.addSeparator();
menuitem = new JMenuItem("Exit (E)", new ImageIcon("cross.png"));
menuitem.setMnemonic(KeyEvent.VK_E);
menuitem.addActionListener( new MenuExitHandler() );
menu.add(menuitem);
timer.schedule(new todoTask(), 0, 2000);
}
class MenuStoreHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
int screenWidth = (int) dim.getWidth();
int screenHeight = (int) dim.getHeight();
JDialog g = new JDialog();
g.setTitle("The Store");
g.setSize(200, 200);
g.setLocation(screenWidth / 2 - 150, screenHeight / 2 - 150);
JButton b = new JButton("Buy");
b.addActionListener( new StoreItem1Handler() );
b.setVisible(true);
g.add(b);
g.setVisible(true);
}
}
class StoreItem1Handler implements ActionListener{
public void actionPerformed(ActionEvent e){
System.out.println("Store-Button 1 pressed.");
}
}
class MenuExitHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
System.exit(1);
}
}
class MenuResetPointHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
points = 0;
repaint();
JOptionPane.showMessageDialog(null, "Points have been reset.");
}
}
public void paint(Graphics g){
g.setColor(Color.WHITE);
bg.paintIcon(this,g,0,0);
g.setColor(Color.BLACK);
g.drawString("Points: " + points, 75, 95);
g.drawString("Version: " + version, 2, 10);
}
public static void main(String[] args){
final MrStanCreateFile g = new MrStanCreateFile();
Runtime.getRuntime().addShutdownHook(new Thread(new Runnable(){
public void run(){
if(h.exists()){
g.openFile();
g.addRecords();
g.closeFile();
}else{
System.out.println(h.getName() + "does not exist, not saving.");
}
}
}, "Shutdown-thread"));
readIt();
//Create new JFrame
JFrame frame = new JFrame();
frame.setTitle("MrStan");
frame.setSize(200, 200);
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.setJMenuBar(menubar);
//Set location of JFrame
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
int screenWidth = (int) dim.getWidth();
int screenHeight = (int) dim.getHeight();
frame.setLocation(screenWidth / 2 - 200, screenHeight / 2 - 200);
//Set ContentPane to JPanel
MrStan panel = new MrStan();
frame.setContentPane(panel);
//Make the user not be able to resize
frame.setResizable(false);
//Make the JFrame visible
frame.setVisible(true);
}
public static void readIt(){
MrStanReadFile r = new MrStanReadFile();
r.openFile();
r.readFile();
r.closeFile();
}
}

Pourquoi est-ce couvrant la TOTALITÉ de mon JDialog? Je suis en utilisant la structure de base que Manager, il faut juste être bien.