adjeventdemo.java

《java事件处理指南》一书的代码,好东西

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

public class AdjEventDemo extends JFrame 
{
   private JScrollBar jsb; 
   private JTextField jtf;
   private JLabel label;
   private JPanel panel;

   public AdjEventDemo()
   {

/*  The JScrollBar registers an AdjustmentListener  */
//用法：JScrollBar(bar的滚动方向，当前滑动块所在的位置，每步跳值，最小值，最大值+每步跳值);
      jsb = new JScrollBar(JScrollBar.VERTICAL, 100, 5, 0, 200);
      jsb.addAdjustmentListener(new JScrollBarListener());
				/*vscroll = new JScrollBar(JScrollBar.VERTICAL); 
               mainPane.add(vscroll,BorderLayout.EAST); 
               vscroll.addAdjustmentListener(this); 
               vmodel = new DefaultBoundedRangeModel(0,1,0,100); 
               vmodel.setExtent(10);//设置滑块的长度 
               vscroll.setModel(vmodel);//也可用这种mvc方法 */
      jtf = new JTextField(3);
      jtf.setEditable(false);
      jtf.setText(""+jsb.getValue());

      label = new JLabel("Darkness Level");
      label.setForeground(Color.black);

      panel = new JPanel();
      panel.setBackground(Color.white);
      panel.add(label);
      panel.add(jtf);
      panel.add(jsb);

      getContentPane().add(panel);

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setBounds(100, 100, 300, 200);
      setVisible(true);
   }

/*  The AdjustmentListener is implemented as an inner class.    */
/*  In the adjustmentValueChanged() method, the AdjusmentEvent  */
/*  is used to obtain the value of the Adjustable object that   */
/*  created the event, in this case the JScrollBar.  The        */
/*  darkness level of the JPanel background is set to the       */
/*  current JScrollBar level.                                   */ 

   class JScrollBarListener implements AdjustmentListener
   {
      public void adjustmentValueChanged(AdjustmentEvent event)
      {
         int level = event.getValue();
         jtf.setText(""+level);
          panel.setBackground(new Color(level, level, level));         
      }
   }

   public static void main(String args[])
   {
      AdjEventDemo adj = new AdjEventDemo();
   }
}