componenteventdemo.java

来自「《java事件处理指南》一书的代码,好东西」· Java 代码 · 共 55 行

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

public class ComponentEventDemo extends JFrame 
{
   private JLabel label;

   public ComponentEventDemo()
   {

/*  A very long label is created and placed on a JFrame  */

      label = new JLabel("This is a very, very long label");
      label.setFont(new Font("Serif", Font.BOLD, 14));
      label.setForeground(Color.black);

      JPanel panel = new JPanel();
      panel.add(label);
      getContentPane().add(panel);

/*  The JFrame registers a ComponentListener    */

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

/*  We're only really interested in the componentResized() method  */ 
/*  so the ComponentListener is implemented as an inner class      */
/*  that extends the ComponentAdapter class. When the JFrame is    */
/*  resized, a ComponentEvent is generated and sent to the         */
/*  componentResized() method.  This method tests to see if the    */
/*  JFrame width is smaller than the JLabel width.  If it is, the  */
/*  JFrame is resized so it is wider than the JLabel.              */

   class CompListener extends ComponentAdapter
   {
      public void componentResized(ComponentEvent event)
      {
         Component comp = event.getComponent(); 
         if ( comp.getWidth() < label.getWidth() )
         {
            comp.setSize( label.getWidth()+100, comp.getHeight() );
         }       
      }
   }

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