moveboxcanvas.java

Java程序设计技巧与开发实例附书源代码。

import java.awt.*;

public class MoveBoxCanvas
    extends Canvas
{
   private final int WIDTH = 30, HEIGHT = 20, INC = 4;
   private int x = 50, y = 50;
   public void paint(Graphics g)
   {
      g.fillRect(x, y, WIDTH, HEIGHT);
      g.drawRect(0, 0, getSize().width - 1, getSize().height - 1);
   }

   public void moveUp()
   {
      if (y > 0)
      {
         y -= INC;
      }
      else
      {
         y = getSize().height - INC;
      }
   }

   public void moveDown()
   {
      if (y < getSize().height - INC)
      {
         y += INC;
      }
      else
      {
         y = 0;
      }
   }

   public void moveLeft()
   {
      if (x > 0)
      {
         x -= INC;
      }
      else
      {
         x = getSize().width - INC;
      }
   }

   public void moveRight()
   {
      if (x < getSize().width - INC)
      {
         x += INC;
      }
      else
      {
         x = 0;
      }
   }
}