documenteventdemo.java

《java事件处理指南》一书的代码,好东西

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

public class DocumentEventDemo extends JFrame 
{
   private JTextArea jta;
   private JTextField jtf;

   public DocumentEventDemo() 
   {

/*  A JTextArea is created and placed on a JFrame.  The Document  */
/*  associated with the JTextArea is obtained The Document        */
/*  registers a DocumentListener.                                 */

      jta = new JTextArea(5,15);
      jta.setLineWrap(true);//行自动下卷
      jta.setWrapStyleWord(true);
      jta.getDocument().addDocumentListener(new DocumentHandler());

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

      JPanel p = new JPanel();
      p.add(new JScrollPane(jta));

      getContentPane().add(p, BorderLayout.CENTER);
      getContentPane().add(jtf, BorderLayout.SOUTH);

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setBounds(100, 100, 300, 250);
      setVisible(true);
   }

/*  The DocumentListener is implemented as an inner class.  When        */
/*  text is added to or removed from the JTextArea, a DocumentEvent     */
/*  is generated and sent to either the insertUpdate() or               */
/*  removeUpdate() methods.  The length and position of the change      */
/*  is written to a JTextField at the bottom of the frame.  The         */
/*  changedUpdate() method is not used so it is implemented as a stub.  */

   class DocumentHandler implements DocumentListener
   {
      public void insertUpdate(DocumentEvent event)
      {
         int length = event.getLength();
         if ( length == 1 )
         {
         jtf.setText("1 character inserted at position "+
                                            event.getOffset());
         }
         else
         {
            jtf.setText(""+event.getLength()+
               " characters inserted at position "+event.getOffset());
         }
      }

      public void removeUpdate(DocumentEvent event)
      {
         jtf.setText(""+event.getLength()+
               " characters deleted at position "+event.getOffset());
      }

      public void changedUpdate(DocumentEvent event) {}
   }

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