ChangeTrackingTest.java Source code

Introduction

Here is the source code for ChangeTrackingTest.java

Source

/*
   This program is a part of the companion code for Core Java 8th ed.
   (http://horstmann.com/corejava)
    
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
    
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
    
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

import java.awt.Color;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

/**
 * @version 1.40 2007-08-05
 * @author Cay Horstmann
 */
public class ChangeTrackingTest {
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                ColorFrame frame = new ColorFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
            }
        });
    }
}

/**
 * A frame with three text fields to set the background color.
 */
class ColorFrame extends JFrame {
    public ColorFrame() {
        setTitle("ChangeTrackingTest");

        DocumentListener listener = new DocumentListener() {
            public void insertUpdate(DocumentEvent event) {
                setColor();
            }

            public void removeUpdate(DocumentEvent event) {
                setColor();
            }

            public void changedUpdate(DocumentEvent event) {
            }
        };

        panel = new JPanel();

        panel.add(new JLabel("Red:"));
        redField = new JTextField("255", 3);
        panel.add(redField);
        redField.getDocument().addDocumentListener(listener);

        panel.add(new JLabel("Green:"));
        greenField = new JTextField("255", 3);
        panel.add(greenField);
        greenField.getDocument().addDocumentListener(listener);

        panel.add(new JLabel("Blue:"));
        blueField = new JTextField("255", 3);
        panel.add(blueField);
        blueField.getDocument().addDocumentListener(listener);

        add(panel);
        pack();
    }

    /**
     * Set the background color to the values stored in the text fields.
     */
    public void setColor() {
        try {
            int red = Integer.parseInt(redField.getText().trim());
            int green = Integer.parseInt(greenField.getText().trim());
            int blue = Integer.parseInt(blueField.getText().trim());
            panel.setBackground(new Color(red, green, blue));
        } catch (NumberFormatException e) {
            // don't set the color if the input can't be parsed
        }
    }

    private JPanel panel;
    private JTextField redField;
    private JTextField greenField;
    private JTextField blueField;
}