Dynamic generation of buttons in Java

Question

I am trying to dynamically generate a form. Basically, I want to load a list of items for purchase, and generate a button for each. I can confirm that the buttons are bein

Answer 1

You can use revalidate(), as shown in this example.

Addendum: Here's my variation on @mKorbel's interesting answer that shows a similar result for GridLayout. It looks like repaint() may be necessary after revalidate().

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

/** @see https://stackoverflow.com/questions/6395105 */
public class ValidateRevalidateRepaint {

    private JPanel center;
    private boolean validate = false;
    private boolean revalidate = true;
    private boolean repaint = true;

    public ValidateRevalidateRepaint() {
        center = new JPanel(new GridLayout(1, 0, 10, 10));
        JFrame f = new JFrame();
        f.setTitle("VRR");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(center, BorderLayout.CENTER);
        f.add(getRadioPanel(), BorderLayout.EAST);
        f.add(getCheckBoxPanel(), BorderLayout.SOUTH);
        makeChange(4);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private JPanel getRadioPanel() {
        JPanel panel = new JPanel(new GridLayout(0, 1));
        ButtonGroup group = new ButtonGroup();
        ActionListener l = new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                JRadioButton radio = (JRadioButton) e.getSource();
                int n = Integer.parseInt(radio.getActionCommand());
                makeChange(n);
            }
        };
        for (int j = 0; j < 4; j++) {
            String s = String.valueOf(j + 1);
            JRadioButton radio = new JRadioButton(s);
            radio.setActionCommand(s);
            radio.addActionListener(l);
            group.add(radio);
            panel.add(radio);
            if (j == 3) {
                group.setSelected(radio.getModel(), true);
            }
        }
        return panel;
    }

    private JPanel getCheckBoxPanel() {
        final String[] operations = {"validate", "revalidate", "repaint"};
        ActionListener l = new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                JCheckBox checkBox = (JCheckBox) e.getSource();
                String ac = checkBox.getActionCommand();
                boolean state = checkBox.isSelected();
                if (ac.equals("validate")) {
                    validate = state;
                }
                if (ac.equals("revalidate")) {
                    revalidate = state;
                }
                if (ac.equals("repaint")) {
                    repaint = state;
                }
            }
        };
        JPanel panel = new JPanel();
        for (int j = 0; j < operations.length; j++) {
            JCheckBox check = new JCheckBox(operations[j]);
            if (j == 0) {
                check.setSelected(false);
            } else {
                check.setSelected(true);
            }
            check.setActionCommand(operations[j]);
            check.addActionListener(l);
            panel.add(check);
        }
        return panel;
    }

    private void makeChange(int number) {
        center.removeAll();
        for (int j = 0; j < number; j++) {
            center.add(getFiller());
        }
        if (validate) {
            center.validate();
        }
        if (revalidate) {
            center.revalidate();
        }
        if (repaint) {
            center.repaint();
        }
    }

    private JPanel getFiller() {
        JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createLineBorder(Color.blue, 5));
        panel.setBackground(Color.red);
        panel.setPreferredSize(new Dimension(50, 50));
        return panel;
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new ValidateRevalidateRepaint();
            }
        });
    }
}