大家帮忙看看程序是怎么回事

Question

/**RubberLine.java**/
import javax.swing.*;
public class RubberLine extends JApplet
{
private static final long serialVersionUID = 1L;
private final int WIDTH=300,HEIGHT=200;
public void init()
{
getContentPane().add(new RubberLinePanel());
setSize(WIDTH, HEIGHT);
}
}
/***RubberLinePanel.java**/
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class RubberLinePanel extends JPanel
{
private static final long serialVersionUID = 6080639662013373301L;
private Point point1=null,point2=null;
public RubberLinePanel()
{
LineListener listener= new LineListener();
addMouseListener(listener);
addMouseListener(listener);
setBackground (Color.cyan);
}
public void paintComponent(Graphics page)
{
super.paintComponent(page);
page.setColor(Color.black);
if(point1!=null && point2!=null)
{
page.drawLine(point1.x, point1.y, point2.x, point2.y);
}
}
private class LineListener implements MouseListener,MouseMotionListener
{
public void mousePressed(MouseEvent event)
{
point1=event.getPoint();
}
public void mouseDragged(MouseEvent event)
{
point2=event.getPoint();
repaint();
}
public void mouseClicked(MouseEvent event){}
public void mouseReleased(MouseEvent event){}
public void mouseEntered(MouseEvent event){}
public void mouseExited(MouseEvent event){}
public void mouseMoved(MouseEvent event){}

}
}
为什么点鼠标没有反应？  代码也没有错误

Answer 1

addMouseListener(listener);
addMouseListener(listener);---> addMouseListener(listener);
addMouseMotionListener(listener);