newlabel2.java

《java事件处理指南》一书的代码,好东西

import javax.swing.*;
import java.awt.*;
import java.beans.*;

public class NewLabel2 extends JLabel implements PropertyChangeListener,
                                                 VetoableChangeListener
{
   private FontColor2 fontColor;

   public NewLabel2(String str, FontColor2 fc)
   {
      super(str);
      fontColor = fc;
      setForeground(fontColor.getColor());

/*  When a NewLabel object is created, its FontColor object       */
/*  registers both a PropertyChangeListener and a                 */
/*  VetoableChangeListener.  These two listeners with implement   */
/*  the color associated with the FontColor object as a           */
/*  constrained property.                                         */

      fontColor.addPropertyChangeListener(this);
      fontColor.addVetoableChangeListener(this);
   }

   public FontColor2 getFontColor()
   {
      return fontColor;
   }

   public void setFontColor(FontColor2 fc)
   {
      fontColor = fc;
   }

/*  The NewLabel2 class serves as a PropertyChangeListener and thus  */
/*  provides an implementation of the propertyChange() method.  If   */
/*  the PropertyChangeEvent was due to a change in the "color"       */
/*  property, the text color of the NewLabel is changed.             */

   public void propertyChange(PropertyChangeEvent event)
   {
      if ( event.getPropertyName().equals("color") )
      {
         setForeground( (Color)event.getNewValue() );
      }
   }

/*  The NewLabel2 class also serves as a VetoableChangeListener and  */
/*  thus provides an implementation of the vetoableChange() method.  */
/*  This method determines if the proposed change is unacceptable.   */
/*  If it is, a PropertyVetoException is thrown.                     */

   public void vetoableChange(PropertyChangeEvent event)
                                    throws PropertyVetoException
   {
      if ( event.getPropertyName().equals("color") )
      {
         Color color = (Color)event.getNewValue();
         if ( color.equals(Color.green) )
         {
            throw new PropertyVetoException("Green is forbidden", event);
         }
      }
   }
}