selfcontainedpanel.java

来自「经典的<<C how to program>一书第三版的例程。」· Java 代码 · 共 72 行

// Fig. 29.21: SelfContainedPanel.java
// A self-contained JPanel class that
// handles its own mouse events.
package com.deitel.chtp3.ch29;

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

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

   public SelfContainedPanel()
   {
      addMouseListener(
         new MouseAdapter() {
            public void mousePressed( MouseEvent e )
            {
               x1 = e.getX();
               y1 = e.getY();
            }

            public void mouseReleased( MouseEvent e )
            {
               x2 = e.getX();
               y2 = e.getY();
               repaint();
            }
         }
      );

      addMouseMotionListener(
         new MouseMotionAdapter() {
            public void mouseDragged( MouseEvent e )
            {
               x2 = e.getX();
               y2 = e.getY();
               repaint();
            }
         }
      );
   }

   public Dimension getPreferredSize()
   {
      return new Dimension( 150, 100 );
   }

   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 ) );
   }
}

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