mouseinpadaptdemo.java

《java事件处理指南》一书的代码,好东西

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

public class MouseInpAdaptDemo extends JFrame 
{
   private JPanel panel; 
   private int startX, startY, endX, endY;

   public MouseInpAdaptDemo()
   {

/*  A JPanel object is placed on a Frame registers a         */
/*  MouseInputListener to receive both motion-oriented and   */
/*  non motion-oriented MouseEvents.                         */

      panel = new JPanel();
      MouseInputHandler listener = new MouseInputHandler();
      panel.addMouseListener(listener);
      panel.addMouseMotionListener(listener);

      getContentPane().add(panel);

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

/*  The MouseInputListener is implemented as an inner class that      */
/*  extends the MouseInputAdapter class.  When the user presses the   */
/*  mouse inside the bounding area of the panel, a MouseEvent is      */
/*  generated and sent to the mousePressed() method.  This method     */
/*  sets the starting point for the line. When the mouse is dragged   */
/*  inside the panel, MouseEvents are generated and sent to the       */
/*  mouseDragged() method which draws a line according to the         */
/*  position of the mouse.  Because the MouseInputAdapter class is    */
/*  used, implementations do not have to be provided for the methods  */
/*  declared in the MouseListener and MouseMotionListener interfaces  */
/*  that aren't needed for this example.                              */

   class MouseInputHandler extends MouseInputAdapter
   {
      public void mousePressed(MouseEvent event)
      {
         startX = event.getX();
         startY = event.getY();
         endX = startX;
         endY = startY;
      }

      public void mouseDragged(MouseEvent event)
      {
         startX = endX;
         startY = endY;
         endX = event.getX();
         endY = event.getY();
         panel.getGraphics().drawLine(startX, startY, endX, endY);
      }
   }

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