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

public class JTextArea5 extends JFrame implements UndoableEditListener,
		DocumentListener {
	private UndoableEdit edit;
	private JTextArea jta;
	private JTextArea message;
	private JMenuItem undoitem;
	private JMenuItem redoitem;

	public JTextArea5() {
		super("JTextArea");
		jta = new JTextArea();
		jta.getDocument().addUndoableEditListener(this);
		jta.getDocument().addDocumentListener(this);
		message = new JTextArea();
		message.setEditable(false);

		JPanel p1 = new JPanel();
		p1.setLayout(new GridLayout(1, 1));
		p1.setBorder(BorderFactory.createTitledBorder("Edit Area"));
		p1.add(new JScrollPane(jta));

		JPanel p2 = new JPanel();
		p2.setLayout(new GridLayout(1, 1));
		p2.setBorder(BorderFactory.createTitledBorder("Message"));
		p2.add(new JScrollPane(message));

		getContentPane().setLayout(new GridLayout(2, 1));
		getContentPane().add(p1);
		getContentPane().add(p2);

		JMenuBar bar = new JMenuBar();
		JMenu theMenu = new JMenu("Edit");
		undoitem = new JMenuItem("Undo");
		redoitem = new JMenuItem("Redo");
		theMenu.add(undoitem);
		theMenu.add(redoitem);
		bar.add(theMenu);
		updateMenuItem();

		setJMenuBar(bar);
		setSize(300, 300);

		undoitem.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ev) {
				edit.undo();
				updateMenuItem();
				message.append("- Undo -\n");
			}
		});

		redoitem.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ev) {
				edit.redo();
				updateMenuItem();
				message.append("- Redo -\n");
			}
		});
	} // end of JTextArea5

	public void undoableEditHappened(UndoableEditEvent ev) {
		StringBuffer buf = new StringBuffer(200);
		edit = ev.getEdit();
		buf.append("undoableEdit:");
		buf.append(edit.getPresentationName());
		buf.append("\n");
		message.append(buf.toString());
		updateMenuItem();
	}// end of undoableEditHappened()

	public void updateMenuItem() {

		if (edit != null) {
			undoitem.setEnabled(edit.canUndo());
			redoitem.setEnabled(edit.canRedo());
			undoitem.setText(edit.getUndoPresentationName());
			redoitem.setText(edit.getRedoPresentationName());
		} else {
			undoitem.setEnabled(false);
			redoitem.setEnabled(false);
			undoitem.setText("Undo");
			redoitem.setText("Redo");
		}
	}// end of updateMenu()

	public void showDE(DocumentEvent de) {
		StringBuffer debuf = new StringBuffer(100);
		debuf.append(de.getType());
		debuf.append("Offset:");
		debuf.append(de.getOffset());
		debuf.append("Length:");
		debuf.append(de.getLength());

		Element Eroot = jta.getDocument().getDefaultRootElement();
		DocumentEvent.ElementChange Echange = de.getChange(Eroot);
		if (Echange == null) {
			debuf.append("(No Element Change)");
		} else {
			debuf.append("Element Change:index");
			debuf.append("Echange.getIndex()");
		}
		debuf.append("\n");
		message.append(debuf.toString());
	}

	public void changedUpdate(DocumentEvent de) {
		showDE(de);
	}

	public void insertUpdate(DocumentEvent de) {
		showDE(de);
	}

	public void removeUpdate(DocumentEvent de) {
		showDE(de);
	}

	public static void main(String[] args) {
		JFrame f = new JTextArea5();
		f.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
		f.show();
	}
}