example18_5.java

不错的教程 适合中高级人员的使用

import java.applet.*;import java.awt.*;
import java.awt.event.*;
public class Example18_5 extends Applet
implements ActionListener,MouseMotionListener
{  int x=-1,y=-1,橡皮擦通知=0,清除通知=0;
   Color c=new Color(255,0,0);int con=3;
   Button b_red,b_blue,b_green,
   清除,b_quit;
   public void init()
   {  addMouseMotionListener(this); 
      b_red=new Button("画红色图形");    
      b_blue=new Button("兰色图形"); 
      b_green=new Button("画绿色图形");  
      b_quit=new Button("橡皮");
      清除=new Button("清除");
      add(b_red); add(b_green); add(b_blue); add(b_quit);add(清除);
      b_red.addActionListener(this); b_green.addActionListener(this);
      b_blue.addActionListener(this); b_quit.addActionListener(this);
      清除.addActionListener(this);
   }
   public void paint(Graphics g)
   {  if(x!=-1&&y!=-1&&橡皮擦通知==0&&清除通知==0)
         {  g.setColor(c); g.fillOval(x,y,con,con);
         }
       else if(橡皮擦通知==1&&清除通知==0)
        {  g.clearRect(x,y,10,10);
        }
       else if(清除通知==1&&橡皮擦通知==0)
        {  g.clearRect(0,0,getSize().width,getSize().height);
        }
   }
   public void mouseDragged(MouseEvent e)
   {  x=(int)e.getX();y=(int)e.getY(); repaint();
   }
    public void mouseMoved(MouseEvent e){ } 
   public void update(Graphics g)
   {  paint(g);
   } 
   public void actionPerformed(ActionEvent e)
   {  if(e.getSource()==b_red)
        {  橡皮擦通知=0;清除通知=0; c=new Color(255,0,0);
        }
      else if(e.getSource()==b_green)
        {  橡皮擦通知=0;清除通知=0;  c=new Color(0,255,0);
        }
      else if(e.getSource()==b_blue)
        {  橡皮擦通知=0;清除通知=0; c=new Color(0,0,255);
        }
      if(e.getSource()==b_quit)
       {   橡皮擦通知=1;清除通知=0 ;
       }
      if(e.getSource()==清除)
       {   清除通知=1; 橡皮擦通知=0;repaint();
       }
   }
}