careteventdemo.java

《java事件处理指南》一书的代码,好东西

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

public class CaretEventDemo extends JFrame implements CaretListener
{
   private JTextField jtf, jtf1, jtf2;

   public CaretEventDemo()
   {
/*  A JTextField is created and placed on a JFrame.  The JTextField  */
/*  registers a CaretListener.  The CaretEventDemo class             */
/*  serves as the CaretListener, so the addCaretListener() method    */
/*  is passed the "this" argument.                                   */

      jtf = new JTextField(20);
      jtf.setBorder(BorderFactory.createLineBorder(Color.black));
      jtf.addCaretListener(this);

      jtf1 = new JTextField(15);
      jtf1.setEditable(false);

      jtf2 = new JTextField(15);
      jtf2.setEditable(false);

      JPanel centerPanel = new JPanel();
      centerPanel.add(jtf);

      JPanel southPanel = new JPanel();
      southPanel.add(jtf1);
      southPanel.add(jtf2);

      getContentPane().add(centerPanel, BorderLayout.CENTER);
      getContentPane().add(southPanel, BorderLayout.SOUTH);

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setBounds(100, 100, 400, 200);
      setVisible(true);
   }

/*  Since the CaretEventDemo class is the CaretListener, it provides     */
/*  an implementation of the caretUpdate() method. Whenever the caret    */
/*  of the upper JTextField is changed, a CaretEvent is generated and    */
/*  sent to this method.  The current caret position and range of any    */
/*  selected text are written to textfields at the bottom of the frame.  */

   public void caretUpdate(CaretEvent event)
   {
       jtf1.setText("caret at "+event.getDot());
       jtf2.setText("selected range ("+event.getMark()+
                                   ","+event.getDot()+")");
   }

   public static void main(String args[])
   {
      CaretEventDemo demo = new CaretEventDemo();
   }
}