Question

Here is my program.This program simply creates a frame using swings in java and create a grid first and adds button to that frame:

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

public class one {
    private static void createAndShowGUI() {
        JFrame frame = new JFrame("HelloWorldSwing");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.setSize(400,400);
        frame.getContentPane().setPreferredSize(new Dimension(500,500));
        frame.pack();
        frame.setVisible(true);
        Container pane=frame.getContentPane();
        pane.setLayout(new GridLayout(5,6));

        JButton[] buttons = new JButton[26];

        String  b[]={"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
        for(int i = 0; i<buttons.length; i++) {
            buttons[i] = new JButton(b[i]);
            buttons[i].setSize(80, 80);
            buttons[i].setActionCommand(b[i]);
            buttons[i].addActionListener(new ActionListener(){
                public void actionPerformed(ActionEvent e) {
                    String choice = e.getActionCommand();
                    JOptionPane.showMessageDialog(null, "You have clicked: "+choice);
                }
            });
            System.out.println("adding button\n");
            pane.add(buttons[i]);
        }

    }
    public static void main(final String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

The program compiles fine.But the button creation i can see only one button that is “A” and rest of the buttons i am not able to see in the pane.

Answer 1

It turns out that this seems to be a race condition and/or system dependent type issue, since it works for others. In any case, the Javadoc for java.awt.Container.add() states:

This method changes layout-related information, and therefore,
invalidates the component hierarchy. If the container has already been
displayed, the hierarchy must be validated thereafter in order to
display the added component.

You should therefore call pane.validate() after you have added all components (or, as MadProgrammer says, execute the setVisible() call after you have added all your components).