Text Undo Manager

• Undoes edits block-by-block (which by instinct are deemed as one collective edit) based on typing intervals by default
• Able to redefine the undo policy/ behaviour (i.e. how streams of characters are undone/ redone as one single edit unit) - two policy options are available: Typing-intervals and Word-boundaries
• Able to override the undo policy on how deletions are remembered with one of these options: Deletion-series, Deletion-keystroke and None.
• Able to enquiry the count of undo/ redo points created
• Able to enquiry the nature/ description of each edit on the undo/ redo lists (e.g. get to know the characters to be undone/ redone next)
• Able to set the limit of the number of edits to be remembered
• Able to reset (discard) all of the undo/ redo points
• Able to register the binding of keyboard shortcuts to the undo and redo operations with the associated JTextComponent
• Automatically integrates the undo-and-redo functionality with the associated JTextComponent without the developer's intervention

• Creating a basic TextUndoManager for a JTextComponent instance

import java.awt.BorderLayout;
import javax.swing.*;
import ngjmy.undo.TextUndoManager;

   public class BasicExample extends JFrame {

      public BasicExample() {
         JTextArea textArea = new JTextArea();
         // Creates a TextUndoManager with an edit storage capacity of 200 which integrates with textArea
         TextUndoManager undoManager = new TextUndoManager(textArea, 200);
         // Registers the default undo key (Ctrl+Z) and redo key (Ctrl+Y) with the text component
         undoManager.registerDefaultKeysMap();
         add(textArea, BorderLayout.CENTER);
    }

    /** Creates and displays the JFrame */
    public static void main(String[] args) {
       JFrame frame = new BasicExample();
       frame.setTitle("Basic Example");
       frame.setSize(500, 300);
       frame.setLocationRelativeTo(null);
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       frame.setVisible(true);
    }

}

• Customizing the TextUndoManager

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import ngjmy.undo.*;
import ngjmy.undo.TextUndoManager.MenuItemFactory;

public class AnotherExample extends JFrame {

    private JLabel label;
    private JTextArea textArea;
    private TextUndoManager undoManager;

    public AnotherExample() {
        label = new JLabel(" ");
        textArea = new JTextArea();

        // Creates a TextUndoManager with a default edit storage capacity of 100 which integrates with textArea
        undoManager = new TextUndoManager(textArea);

        // Undoes edits based on word boundaries, i.e. a word at a time
        undoManager.setUndoPolicy(UndoPolicy.WORD_BOUNDARIES);
        // Undoes a deletion entry at a time
        undoManager.setDeletionPattern(DeletionPattern.DELETION_KEYSTROKE);

        // Registers the undo key (Ctrl+Z) with the text component
        undoManager.registerUndoKeyMap(KeyStroke.getKeyStroke(KeyEvent.VK_Z, KeyEvent.CTRL_DOWN_MASK));
        // Registers the redo key (Ctrl+X) with the text component
        undoManager.registerRedoKeyMap(KeyStroke.getKeyStroke(KeyEvent.VK_X, KeyEvent.CTRL_DOWN_MASK));

        // Creates a popup menu
        JPopupMenu popupMenu = new JPopupMenu();
        // Gets the menu item factory for undoManager
        MenuItemFactory menuItemFactory = undoManager.getMenuItemFactory();
        // Creates a ready-made undo menu item using the factory and adds it to the popup menu
        popupMenu.add(menuItemFactory.createUndoMenuItem());
        // Creates a ready-made redo menu item and adds it to the popup menu
        popupMenu.add(menuItemFactory.createRedoMenuItem());

        // Creates a listener that listens for undo and redo events from undoManager
        undoManager.addTextUndoListener(new TextUndoListener() {
            @Override
            public void undoPerformed(BasicEdit edit) {
                updateLabelText(edit, "Undo");
            }

            @Override
            public void redoPerformed(BasicEdit edit) {
                updateLabelText(edit, "Redo");
            }
        });

        // Associates the popup menu with textArea
        textArea.setComponentPopupMenu(popupMenu);

        add(textArea, BorderLayout.CENTER);
        add(label, BorderLayout.SOUTH);
    }

    private void updateLabelText(BasicEdit edit, String type) {
        label.setText("Last Operation: " + type + " " + edit.getType() + " " + edit.getContent() + ".");
    }

     /** Creates and displays the JFrame */
    public static void main(String[] args) {
        JFrame frame = new AnotherExample();
        frame.setTitle("Another Example");
        frame.setSize(500, 300);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

1. Copy dist/TextUndoManager.jar and dist/lib to the root directory of your application project.
2. For Eclipse, in Package Explorer right click on TextUndoManager.jar and select Build Path Add to Build Path. For Netbeans, in Project right-click on the project and select Properties. Go to Libraries, in Compile click Add JAR/ Folder and import TextUndoManager.jar.