test.java

《Java2图形设计卷II：Swing》配套光盘源码

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

public class Test extends JApplet {
	private JTextArea textArea = new JTextArea("some content");
	private Document document = textArea.getDocument();
	private UndoManager undoManager = new UndoManager();
	private UndoLastAction undoAction = new UndoLastAction();
	private RedoAction redoAction = new RedoAction();

	public Test() {
		Container contentPane = getContentPane();

		createMenu();
		contentPane.add(textArea, BorderLayout.CENTER);

		textArea.setFont(new Font("Dialog", Font.PLAIN, 24));
		document.addUndoableEditListener(
									  new UndoableEditListener() {
			public void undoableEditHappened(UndoableEditEvent e){
				undoManager.addEdit(e.getEdit());
				undoAction.update();
				redoAction.update();
			}
		});
	}
	private void createMenu() {
		JMenuBar menuBar = new JMenuBar();
		JMenu editMenu = new JMenu("Edit");

		editMenu.add(new DefaultEditorKit.CutAction());
		editMenu.add(new DefaultEditorKit.CopyAction());
		editMenu.add(new DefaultEditorKit.PasteAction());

		editMenu.addSeparator();

		editMenu.add(undoAction);
		editMenu.add(redoAction);

		menuBar.add(editMenu);
		setJMenuBar(menuBar);
	}
	class RedoAction extends AbstractAction {
		public RedoAction() {
			super("Redo");
			update();
		}
		public void actionPerformed(ActionEvent e) {
			undoManager.redo();
			undoAction.update();
			update();
		}
		public void update() {
			boolean canRedo = undoManager.canRedo();

			if(canRedo) {
				setEnabled(true);
				putValue(Action.NAME, 
						 undoManager.getRedoPresentationName());
			}
			else {
				setEnabled(false);
				putValue(Action.NAME, "Redo");
			}
		}
	}
	class UndoLastAction extends AbstractAction {
		public UndoLastAction() {
			super("Undo");
			update();
		}
		public void actionPerformed(ActionEvent e) {
			undoManager.undo();
			redoAction.update();
			update();
		}
		public void update() {
			boolean canUndo = undoManager.canUndo();

			if(canUndo) {
				setEnabled(true);
				putValue(Action.NAME, 
						 undoManager.getUndoPresentationName());
			}
			else {
				setEnabled(false);
				putValue(Action.NAME, "Undo");
			}
		}
	}
}