slidecolorpanel.java

Java 程序设计教程（第五版）EXAMPLESchap9源码

//********************************************************************
//  SlideColorPanel.java       Authors: Lewis/Loftus
//
//  Represents the slider control panel for the SlideColor program.
//********************************************************************

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

public class SlideColorPanel extends JPanel
{
   private JPanel controls, colorPanel;
   private JSlider rSlider, gSlider, bSlider;
   private JLabel rLabel, gLabel, bLabel;

   //-----------------------------------------------------------------
   //  Sets up the sliders and their labels, aligning them along
   //  their left edge using a box layout.
   //-----------------------------------------------------------------
   public SlideColorPanel()
   {
      rSlider = new JSlider (JSlider.HORIZONTAL, 0, 255, 0);
      rSlider.setMajorTickSpacing (50);
      rSlider.setMinorTickSpacing (10);
      rSlider.setPaintTicks (true);
      rSlider.setPaintLabels (true);
      rSlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      gSlider = new JSlider (JSlider.HORIZONTAL, 0, 255, 0);
      gSlider.setMajorTickSpacing (50);
      gSlider.setMinorTickSpacing (10);
      gSlider.setPaintTicks (true);
      gSlider.setPaintLabels (true);
      gSlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      bSlider = new JSlider (JSlider.HORIZONTAL, 0, 255, 0);
      bSlider.setMajorTickSpacing (50);
      bSlider.setMinorTickSpacing (10);
      bSlider.setPaintTicks (true);
      bSlider.setPaintLabels (true);
      bSlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      SliderListener listener = new SliderListener();
      rSlider.addChangeListener (listener);
      gSlider.addChangeListener (listener);
      bSlider.addChangeListener (listener);

      rLabel = new JLabel ("Red: 0");
      rLabel.setAlignmentX (Component.LEFT_ALIGNMENT);
      gLabel = new JLabel ("Green: 0");
      gLabel.setAlignmentX (Component.LEFT_ALIGNMENT);
      bLabel = new JLabel ("Blue: 0");
      bLabel.setAlignmentX (Component.LEFT_ALIGNMENT);

      controls = new JPanel();
      BoxLayout layout = new BoxLayout (controls, BoxLayout.Y_AXIS);
      controls.setLayout (layout);
      controls.add (rLabel);
      controls.add (rSlider);
      controls.add (Box.createRigidArea (new Dimension (0, 20)));
      controls.add (gLabel);
      controls.add (gSlider);
      controls.add (Box.createRigidArea (new Dimension (0, 20)));
      controls.add (bLabel);
      controls.add (bSlider);

      colorPanel = new JPanel();
      colorPanel.setPreferredSize (new Dimension (100, 100));
      colorPanel.setBackground (new Color (0, 0, 0));
      
      add (controls);
      add (colorPanel);
   }

   //*****************************************************************
   //  Represents the listener for all three sliders.
   //*****************************************************************
   private class SliderListener implements ChangeListener
   {
      private int red, green, blue;

      //--------------------------------------------------------------
      //  Gets the value of each slider, then updates the labels and
      //  the color panel.
      //--------------------------------------------------------------
      public void stateChanged (ChangeEvent event)
      {
         red = rSlider.getValue();
         green = gSlider.getValue();
         blue = bSlider.getValue();

         rLabel.setText ("Red: " + red);
         gLabel.setText ("Green: " + green);
         bLabel.setText ("Blue: " + blue);

         colorPanel.setBackground (new Color (red, green, blue));
      }
   }
}