import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;
class UndoableTextArea extends JTextArea implements UndoableEditListener, FocusListener,
KeyListener {
private UndoManager m_undoManager;
public UndoableTextArea() {
this(new String());
}
public UndoableTextArea(String text) {
super(text);
getDocument().addUndoableEditListener(this);
this.addKeyListener(this);
this.addFocusListener(this);
}
private void createUndoMananger() {
m_undoManager = new UndoManager();
m_undoManager.setLimit(10);
}
private void removeUndoMananger() {
m_undoManager.end();
}
public void focusGained(FocusEvent fe) {
createUndoMananger();
}
public void focusLost(FocusEvent fe) {
removeUndoMananger();
}
public void undoableEditHappened(UndoableEditEvent e) {
m_undoManager.addEdit(e.getEdit());
}
public void keyPressed(KeyEvent e) {
if ((e.getKeyCode() == KeyEvent.VK_Z) && (e.isControlDown())) {
try {
m_undoManager.undo();
} catch (CannotUndoException cue) {
Toolkit.getDefaultToolkit().beep();
}
}
if ((e.getKeyCode() == KeyEvent.VK_Y) && (e.isControlDown())) {
try {
m_undoManager.redo();
} catch (CannotRedoException cue) {
Toolkit.getDefaultToolkit().beep();
}
}
}
public void keyReleased(KeyEvent e) {
}
public void keyTyped(KeyEvent e) {
}
}
public class Main extends JFrame {
UndoableTextArea m_undoableTextArea = new UndoableTextArea();
public Main() {
JScrollPane sc = new JScrollPane(m_undoableTextArea);
getContentPane().setLayout(new BorderLayout(10, 10));
getContentPane()
.add(BorderLayout.NORTH, new JLabel("Press, CTRL+Z to Undo, CTRL+Y to Redo..."));
getContentPane().add(BorderLayout.CENTER, sc);
}
public static void main(String[] arg) {
Main m = new Main();
m.setVisible(true);
m.setSize(new Dimension(400, 300));
m.validate();
}
}