javax.swing.undo类 使用实例 - 转载

import java.awt.BorderLayout; 
import java.awt.GridLayout; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
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.UndoManager; 

public class UndoRedoTextArea extends JFrame { 
 protected JTextArea textArea = new JTextArea(); 

 protected UndoManager undoManager = new UndoManager(); 

 protected JButton undoButton = new JButton("Undo"); 

 protected JButton redoButton = new JButton("Redo"); 

 public UndoRedoTextArea() { 
   super("Undo/Redo Demo"); 

   undoButton.setEnabled(false); 
   redoButton.setEnabled(false); 

   JPanel buttonPanel = new JPanel(new GridLayout()); 
   buttonPanel.add(undoButton); 
   buttonPanel.add(redoButton); 

   JScrollPane scroller = new JScrollPane(textArea); 

   getContentPane().add(buttonPanel, BorderLayout.NORTH); 
   getContentPane().add(scroller, BorderLayout.CENTER); 

   textArea.getDocument().addUndoableEditListener( 
       new UndoableEditListener() { 
         public void undoableEditHappened(UndoableEditEvent e) { 
           undoManager.addEdit(e.getEdit()); 
           updateButtons(); 
         } 
       }); 

   undoButton.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
       try { 
         undoManager.undo(); 
       } catch (CannotRedoException cre) { 
         cre.printStackTrace(); 
       } 
       updateButtons(); 
     } 
   }); 

   redoButton.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
       try { 
         undoManager.redo(); 
       } catch (CannotRedoException cre) { 
         cre.printStackTrace(); 
       } 
       updateButtons(); 
     } 
   }); 

   setSize(400, 300); 
   setVisible(true); 
 } 

 public void updateButtons() { 
   undoButton.setText(undoManager.getUndoPresentationName()); 
   redoButton.setText(undoManager.getRedoPresentationName()); 
   undoButton.setEnabled(undoManager.canUndo()); 
   redoButton.setEnabled(undoManager.canRedo()); 
 } 

 public static void main(String argv[]) { 
   new UndoRedoTextArea(); 
 } 
}