我就想知道mouseDragged方法中else里面的px1=e.getX()和py1=e.getY() 这两句是干嘛用的？前面mouseMoved方法中不是给px1,py1赋值过了吗，这里再赋值一次是为了什么？而且这里再次赋值了之后下面 px2=Math.abs(e.getX()-px1); py2=Math.abs(e.getY()-py1); 这两句我也是一脸懵逼啊，前边再次赋值的时候不是 px1=e.getX()，py1=e.getY()吗，那相减不是等于0嘛？！我是菜鸟啊不是很理解其中的意思，希望各位大神来帮我解释下，万分感谢！！！
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class App14_4 extends JFrame implements MouseMotionListener,MouseListener
{
static App14_4 frm=new App14_4();
int px1,py1,px2,py2,status=0;
int rpx1,rpy1,rpx2,rpy2;
public static void main(String[] args)
{
frm.setTitle("鼠标拖动画椭圆");
frm.setSize(250,230);
frm.addMouseListener(frm);
frm.addMouseMotionListener(frm);
frm.setVisible(true);
frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void mouseMoved(MouseEvent e) {
// TODO Auto-generated method stub
px1=e.getX();
py1=e.getY();
status=0;
}
public void mouseDragged(MouseEvent e)
{
Graphics g=this.getGraphics();
g.setColor(Color.YELLOW);
g.setXORMode(Color.BLACK);
if(status==1)
g.drawOval(px1, py1, px2, py2);
else{
px1=e.getX();
py1=e.getY();
status=1;
}
px2=Math.abs(e.getX()-px1);
py2=Math.abs(e.getY()-py1);
g.drawOval(px1, py1, px2, py2);
rpx1=px1;rpy1=py1;rpx2=px2;rpy2=py2;
}
public void mouseReleased(MouseEvent e)
{
Graphics g=this.getGraphics();
g.setColor(Color.RED);
g.drawOval(rpx1, rpy1, rpx2, rpy2);
}
@Override
public void mouseClicked(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mousePressed(MouseEvent e) {
// TODO Auto-generated method stub
}
}
