Invisible JRadioButtons

Question

I have three different JRadioButtons that are all added to one JPanel. When I add the JPanel to the JFrame, only the lvl3 JRadioButton shows up. If I comment that line out, then none of the buttons show up. Is there something I'm doing wring? or should I use JRaduiButtonGroups?

import javax.swing.*;
import java.awt.*;
import javax.swing.event.*;
import java.awt.event.*;
import java.util.Timer;


public class CastleDefenders {
static Timer timer;
Toolkit tlkt;
private JMenuBar mb2 = new JMenuBar();
private static boolean startGame = false;
private static JFrame f = new JFrame("Castle Defenders");
private static JFrame g = new JFrame("Castle Defenders");
private JRadioButton lvl1 = new JRadioButton("Easy");
private JRadioButton lvl2 = new JRadioButton("Normal");
private JRadioButton lvl3 = new JRadioButton("Hard");
private JPanel pnl = new JPanel();
private JTextField lbl = new JTextField("Welcome to Castle Defenders!");
private JButton btn = new JButton("START");
private JMenuBar mb = new JMenuBar();
private JMenu mnuFile = new JMenu("File");
private JPanel pnl2 = new JPanel();
private JMenuItem mnuItemQuit = new JMenuItem("Quit");
private JMenu mnuHelp = new JMenu("Help");
private JMenuItem mnuItemAbout = new JMenuItem("About");

public CastleDefenders(){
    lvl1.setToolTipText("Play the game on Easy");
    lvl2.setToolTipText("Play the game on Normal");
    lvl3.setToolTipText("Play the game on Hard");
    pnl2.add(lvl1);
    pnl2.add(lvl2);
    pnl2.add(lvl3);
    tlkt = Toolkit.getDefaultToolkit();
    timer = new Timer();
    pnl2.setBounds(50, 5, 1, 10);
    btn.setBounds(220, 240, 5, 1);
    f.setJMenuBar(mb2);
    g.setJMenuBar(mb2);
    mnuFile.add(mnuItemQuit);
    mnuHelp.add(mnuItemAbout);
    mb.add(mnuFile);
    mb.add(mnuHelp);
    mb2.add(mnuFile);
    mb2.add(mnuHelp);
    pnl.add(btn);
    pnl2.add(lbl);
    lbl.setBounds(0, 240, 10, 2);
    lbl.setEditable(false);
    f.getContentPane().setLayout(new BorderLayout());
    f.getContentPane().add(pnl, BorderLayout.CENTER);       
    f.addWindowListener(new ListenCloseWdw());
    g.getContentPane().setLayout(new BorderLayout());
    g.getContentPane().add(pnl2);   
    g.addWindowListener(new ListenCloseWdw());
    mnuItemAbout.addActionListener(new GetAboutInfo());     
    btn.addActionListener(new GetButtonClick());    
    mnuItemQuit.addActionListener(new ListenMenuQuit());


}

public class GetButtonClick implements ActionListener{
    public void actionPerformed(ActionEvent e){
        startGame = true;
        //JOptionPane.showMessageDialog(null, "WIP");
    }
}
public class GetAboutInfo implements ActionListener{
    public void actionPerformed(ActionEvent e){
        JOptionPane.showMessageDialog(null, "Made By Byron Lathi");
    }
}
public class ListenCloseWdw extends WindowAdapter{
    public void windowClosing(WindowEvent e) {
        System.exit(0);
    }
}
public class ListenMenuQuit implements ActionListener{
    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}
public void launchFrameF(){
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.pack();
    f.setBounds(0, 0, 640, 680);
}
public void launchFrameG(){
    g.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    g.pack();
    g.setBounds(0, 0, 640, 680);
    g.getContentPane().add(lvl1).setBounds(1, 1, 1, 1);
    g.getContentPane().add(lvl2).setBounds(2, 2, 1, 1);
    g.getContentPane().add(lvl3).setBounds(3, 3, 1/2, 1/2);

}
public static void main(String args[]) {
    final CastleDefenders main = new CastleDefenders();
    main.launchFrameF();
    f.setVisible(true);
    do {
        System.out.print("");
    }while(startGame == false);
    if (startGame == true){
        JOptionPane.showMessageDialog(null, "We've come so far...");
        f.setVisible(false);
        main.launchFrameG();
        g.setVisible(true);
    }

}

}

Answer 1

In your code you already have those radio button in the pnl2 JPanel and this panel already added to the frame content pane. Re-adding the radio buttons again by calling getContentPane().add() method in the launchFrameG() method replace the content pane of the frame, which make your panel got replaced. Add only the last added component remain in the content pane.