Hi All,

If you are adding JButton ,JLabel or JComboBox etc dynamically or adding them during runtime For example

public class Main {

  public JPanel buttonPanel ;


  public static void main(String[] args) {
    JFrame frame = new JFrame();

    int gridSize = 3; // try 4 or 5, etc. buttons are always 50x50

    JPanel panel = new JPanel(new GridLayout(gridSize, gridSize));
    panel.setPreferredSize(new Dimension(500, 500));


   buttonPanel = new JPanel(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
   c.anchor = GridBagConstraints.CENTER;

    JButton button = new JButton();
    button.setPreferredSize(new Dimension(50, 50));
    buttonPanel.add(button, c);
   button.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e)
    {

      JPanel buttonPanel = new JPanel(new GridBagLayout());
       GridBagConstraints c = new GridBagConstraints();
      c.anchor = GridBagConstraints.CENTER;

       JButton dynamic = new JButton();
       dynamic.setPreferredSize(new Dimension(50, 50));
       buttonPanel.add(button, c);
    }
   });
    panel.add(buttonPanel);

    frame.setContentPane(panel);
    frame.pack();
    frame.setVisible(true);
  }
}

In Above example, when you clicked button then you added one more button to screen but when you run this example you will see nothing happened after clicking on a button. Whenever you add any component to screen then you have to revalidate and repaint that component.

After calling revalidate and repaint function, the code will look like :-

public class Main {

      public JPanel buttonPanel ;


      public static void main(String[] args) {
        JFrame frame = new JFrame();

        int gridSize = 3; // try 4 or 5, etc. buttons are always 50x50

        JPanel panel = new JPanel(new GridLayout(gridSize, gridSize));
        panel.setPreferredSize(new Dimension(500, 500));


       buttonPanel = new JPanel(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
       c.anchor = GridBagConstraints.CENTER;

        JButton button = new JButton();
        button.setPreferredSize(new Dimension(50, 50));
        buttonPanel.add(button, c);
       button.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e)
        {

          JPanel buttonPanel = new JPanel(new GridBagLayout());
           GridBagConstraints c = new GridBagConstraints();
          c.anchor = GridBagConstraints.CENTER;

           JButton dynamic = new JButton();
           dynamic.setPreferredSize(new Dimension(50, 50));
           buttonPanel.add(button, c);

//Just call this two function to repaint buttonPanel
           buttonPanel.revalidate();
           buttonPanel.repaint();
        }
       });
        panel.add(buttonPanel);

        frame.setContentPane(panel);
        frame.pack();
        frame.setVisible(true);
      }
    }