mouseinputdemo.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 MouseInputDemo extends JFrame 
{
   private JPanel panel; 
   private int startX, startY, endX, endY;

   public MouseInputDemo()
   {

/*  A JPanel object is placed on a Frame and 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.  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.  Every method        */
/*  declared in the MouseListener and MouseMotionListener interfaces  */
/*  must be given an implementation.  The other five methods are      */
/*  implemented as stub methods.                                      */

   class MouseInputHandler implements MouseInputListener
   {
      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 void mouseClicked(MouseEvent event) {}
      public void mouseEntered(MouseEvent event) {}
      public void mouseExited(MouseEvent event) {}
      public void mouseReleased(MouseEvent event) {}
      public void mouseMoved(MouseEvent event) {}
   }

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