undoablejcheckboxedit.java

《java事件处理指南》一书的代码,好东西

import javax.swing.*;
import javax.swing.undo.*;

public class UndoableJCheckBoxEdit extends AbstractUndoableEdit
{
/*  The UndoableJCheckBoxEdit class defines two variables, an    */
/*  UndoableJCheckBox which serves as a reference to the object  */
/*  that generated the event and a boolean which represents the  */
/*  selected state of the event source.                          */

   private boolean selected;
   private UndoableJCheckBox jcb;

/*  The UndoableJCheckBoxEdit constructor is passed a reference     */
/*  to the object that generated the event.  The selected variable  */
/*  is set based on the selected state of the event source.         */

   public UndoableJCheckBoxEdit(UndoableJCheckBox checkbox) 
   {
      jcb = checkbox;
      selected = jcb.isSelected();
   }

/*  The redo() method is overridden to include a change to the   */
/*  selected state of the event source.                          */

   public void redo() throws CannotRedoException
   {
      super.redo();
      jcb.setSelected(selected);
   }

/*  The undo() method is overridden to include a change to the   */
/*  selected state of the event source.                          */

   public void undo() throws CannotRedoException
   {
      super.undo();
      jcb.setSelected(!selected);
   }
}