listener.java

java经典的源代码 我非常喜欢这个源代码 对于编程很有好处

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class listener extends Applet implements  ActionListener,MouseMotionListener{
  int x=-1,y=-1,rubber=0,clear=0;
  Color c=new Color(255,0,0);
  int con=3;
  Button redbutton,bluebutton,greenbutton,rubberbutton,clearbutton;
  public void init(){
    addMouseMotionListener(this);
    redbutton=new Button("红色");
    bluebutton=new Button("蓝色");
    greenbutton=new Button("绿色");
    rubberbutton=new Button("橡皮");
    clearbutton=new Button("清除");
    add(redbutton);
    add(bluebutton);
    add(greenbutton);
    add(rubberbutton);
    add(clearbutton);
    redbutton.addActionListener(this);
    bluebutton.addActionListener(this);
    greenbutton.addActionListener(this);
    rubberbutton.addActionListener(this);
    clearbutton.addActionListener(this);
    setSize(640,480);
  }//end of init
  public void paint(Graphics g){
    if(rubber==0&&clear==0){
      g.setColor(c);
      g.fillOval(x,y,con,con);
    }//end of if
    else if(rubber==1&&clear==0){
      g.clearRect(x,y,10,10);
    }
    else if(rubber==0&&clear==1){
      g.clearRect(0,0,getSize().width,getSize().height);
    }
  }//end of paint
  public void mouseDragged(MouseEvent e){
    x=(int)e.getX();
    y=(int)e.getY();
    repaint();
  }//end of mouseDragged

  public void mouseMoved(MouseEvent e){
  }
  public void  update(Graphics g){
    paint(g);
  }
  public void actionPerformed(ActionEvent e){
    if(e.getSource()==redbutton){
      rubber=clear=0;
      c=new Color(255,0,0);
    }//end of if
    else if(e.getSource()==bluebutton){
      rubber=clear=0;
      c=new Color(0,0,255);
    }
    else if(e.getSource()==greenbutton){
      rubber=clear=0;
      c=new Color(0,255,0);
    }
    else if(e.getSource()==rubberbutton){
      rubber=1;
      clear=0;
    }
    else if(e.getSource()==clearbutton){
      rubber=0;
      clear=1;
      repaint();
    }
  }
}