Java Swing dialogs

Dialog windows or dialogs are an indispensable part of most modern GUI applications. A dialog is defined as a conversation between two or more persons. In a computer application a dialog is a window which is used to "talk" to the application. A dialog is used to input data, modify data, change the application settings etc. Dialogs are important means of communication between a user and a computer program. 

In Java Swing toolkit, we can create two kinds of dialogs. Custom dialogs and standard dialogs. Custom dialogs are dialogs, created by the programmer. They are based on the JDialog class. Standard dialogs preedefined dialogs available in the Swing toolkit. For example JColorChooser or JFileChooser. These are dialogs for common programming tasks like showing text, receiving input , loading and saving files etc. They save programmer's time and enhance using some standard behaviour.

There are two basic types of dialogs. Modal and modeless. Modal dialogs block input to other top level windows. Modeless dialogs allow input to other windows. What type of dialog to use, depends on the circumstances. An open file dialog is a good example of a modal dialog. While choosing a file to open, no other operation should be permitted. A typical modeless dialog is a find text dialog. It is handy to have the ability to move the cursor in the text control and define, where to start the finding of the particular text.

A simple custom dialog

In the following example we create a simple custom dialog. It is a sample about dialog, found in most GUI applications, usually located in the help menu. 

package zetcode;

import java.awt.Dimension;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;

import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.SwingUtilities;

class AboutDialog extends JDialog {

    public AboutDialog() {

        initUI();
    }

    public final void initUI() {

        setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS));

        add(Box.createRigidArea(new Dimension(0, 10)));

        ImageIcon icon = new ImageIcon("notes.png");
        JLabel label = new JLabel(icon);
        label.setAlignmentX(0.5f);
        add(label);

        add(Box.createRigidArea(new Dimension(0, 10)));

        JLabel name = new JLabel("Notes, 1.23");
        name.setFont(new Font("Serif", Font.BOLD, 13));
        name.setAlignmentX(0.5f);
        add(name);

        add(Box.createRigidArea(new Dimension(0, 50)));

        JButton close = new JButton("Close");
        close.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent event) {
                dispose();
            }
        });

        close.setAlignmentX(0.5f);
        add(close);

        setModalityType(ModalityType.APPLICATION_MODAL);

        setTitle("About Notes");
        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        setLocationRelativeTo(null);
        setSize(300, 200);
    }
}

public class SimpleDialog extends JFrame {

    public SimpleDialog() {

        initUI();
    }

    public final void initUI() {

        JMenuBar menubar = new JMenuBar();

        JMenu file = new JMenu("File");
        file.setMnemonic(KeyEvent.VK_F);

        JMenu help = new JMenu("Help");
        help.setMnemonic(KeyEvent.VK_H);

        JMenuItem about = new JMenuItem("About");
        help.add(about);

        about.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent event) {
                AboutDialog ad = new AboutDialog();
                ad.setVisible(true);
            }
        });

        menubar.add(file);
        menubar.add(help);
        setJMenuBar(menubar);

        setTitle("Simple Dialog");
        setSize(300, 200);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                SimpleDialog sd = new SimpleDialog();
                sd.setVisible(true);
            }
        });
    }
}

Here we display the about dialog, from the menu of the main frame.

Source : http://zetcode.com