EditUndoManager.java

package gsingh.learnkirtan.ui.shabadeditor.tableeditor;

import java.awt.event.ActionEvent;
import java.util.LinkedList;
import java.util.List;

import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;
import javax.swing.undo.UndoableEdit;

@SuppressWarnings("serial")
public class EditUndoManager extends UndoManager {
	protected Action undoAction;
	protected Action redoAction;
	
	private List<UndoEventListener> listeners = new LinkedList<UndoEventListener>();

	public interface UndoEventListener {
		public void undoEventOccurred();
	}

	public EditUndoManager() {
		this.undoAction = new UndoAction(this);
		this.redoAction = new RedoAction(this);

		synchronizeActions(); // to set initial names
	}

	public void addUndoEventListener(UndoEventListener l) {
		listeners.add(l);
	}

	public Action getUndoAction() {
		return undoAction;
	}

	public Action getRedoAction() {
		return redoAction;
	}

	@Override
	public boolean addEdit(UndoableEdit anEdit) {
		try {
			return super.addEdit(anEdit);
		} finally {
			synchronizeActions();
		}
	}

	@Override
	protected void undoTo(UndoableEdit edit) throws CannotUndoException {
		try {
			super.undoTo(edit);
		} finally {
			synchronizeActions();
		}
	}

	@Override
	protected void redoTo(UndoableEdit edit) throws CannotRedoException {
		try {
			super.redoTo(edit);
		} finally {
			synchronizeActions();
		}
	}

	@Override
	public void discardAllEdits() {
		super.discardAllEdits();
		synchronizeActions();
	}

	protected void synchronizeActions() {
		undoAction.setEnabled(canUndo());
		undoAction.putValue(Action.NAME, getUndoPresentationName());

		redoAction.setEnabled(canRedo());
		redoAction.putValue(Action.NAME, getRedoPresentationName());

		for (UndoEventListener l : listeners) {
			l.undoEventOccurred();
		}
	}

	public class UndoAction extends AbstractAction {
		protected final UndoManager manager;

		public UndoAction(UndoManager manager) {
			this.manager = manager;
		}

		public void actionPerformed(ActionEvent e) {
			try {
				manager.undo();
			} catch (CannotUndoException ex) {
				ex.printStackTrace();
			}
		}
	}

	public class RedoAction extends AbstractAction {
		protected final UndoManager manager;

		public RedoAction(UndoManager manager) {
			this.manager = manager;
		}

		public void actionPerformed(ActionEvent e) {
			try {
				manager.redo();
			} catch (CannotRedoException ex) {
				ex.printStackTrace();
			}
		}
	}
}