selfcontainedpanel.java

这是java的一本书上的源代码

// Fig. 14.4: SelfContainedPanel.java
// A self-contained JPanel class that handles its own mouse events.
package com.deitel.jhtp5.ch14;

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

public class SelfContainedPanel extends JPanel {
   private int x1, y1, x2, y2;

   // set up mouse event handling for SelfContainedPanel
   public SelfContainedPanel()
   {
      // set up mouse listener
      addMouseListener(

         new MouseAdapter() {  // anonymous inner class 

            // handle mouse press event
            public void mousePressed( MouseEvent event )
            {
               x1 = event.getX();
               y1 = event.getY();
            }

            // handle mouse release event
            public void mouseReleased( MouseEvent event )
            {
               x2 = event.getX();
               y2 = event.getY();
               repaint();
            }

         } // end anonymous inner class

      ); // end call to addMouseListener

      // set up mouse motion listener
      addMouseMotionListener(

         new MouseMotionAdapter() {  // anonymous inner class 
 
            // handle mouse drag event
            public void mouseDragged( MouseEvent event )
            {
               x2 = event.getX();
               y2 = event.getY();
               repaint();
            }

         } // end anonymous inner class

      ); // end call to addMouseMotionListener

   } // end constructor SelfContainedPanel

   // return preferred width and height of SelfContainedPanel
   public Dimension getPreferredSize()
   {
      return new Dimension( 150, 100 );
   }

   // paint an oval at the specified coordinates
   public void paintComponent( Graphics g )
   {
      super.paintComponent( g );

      g.drawOval( Math.min( x1, x2 ), Math.min( y1, y2 ),
         Math.abs( x1 - x2 ), Math.abs( y1 - y2 ) );
   }

} // end class SelfContainedPanel


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