lightbulbpanel.java

Java 程序设计教程（第五版）EXAMPLESchap10源码

//********************************************************************
//  LightBulbPanel.java       Author: Lewis/Loftus
//
//  Represents the image for the LightBulb program.
//********************************************************************

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

public class LightBulbPanel extends JPanel
{
   private boolean on;
   private ImageIcon lightOn, lightOff;
   private JLabel imageLabel;

   //-----------------------------------------------------------------
   //  Constructor: Sets up the images and the initial state.
   //-----------------------------------------------------------------
   public LightBulbPanel()
   {
      lightOn = new ImageIcon ("lightBulbOn.gif");
      lightOff = new ImageIcon ("lightBulbOff.gif");

      setBackground (Color.black);

      on = true;
      imageLabel = new JLabel (lightOff);
      add (imageLabel);
   }

   //-----------------------------------------------------------------
   //  Paints the panel using the appropriate image.
   //-----------------------------------------------------------------
   public void paintComponent (Graphics page)
   {
      super.paintComponent(page);

      if (on)
         imageLabel.setIcon (lightOn);
      else
         imageLabel.setIcon (lightOff);
   }

   //-----------------------------------------------------------------
   //  Sets the status of the light bulb.
   //-----------------------------------------------------------------
   public void setOn (boolean lightBulbOn)
   {
      on = lightBulbOn;
   }
}