鼠标点击屏幕某个地方，在这个地方画一个圆点，为什么圆点跟鼠标的位置有偏移呢？

Question

import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
public class Test{
private JButton jb=new JButton("按钮");
private Point p=null;
@SuppressWarnings("serial")
public Test(){
final JFrame jf=new JFrame(){
@Override
public void paint(Graphics g){
super.paint(g);
if(p!=null){
jb.setLocation(p.x,p.y);
}
}
};
jb.setSize(64,30);
jf.setLayout(null);
jb.setVisible(false);
jf.add(jb);
jf.addMouseListener(new MouseAdapter(){
@Override
public void mouseClicked(MouseEvent e){
if(p==null)
p=new Point();
p=e.getPoint();
jb.setVisible(true);
jf.validate();
jf.repaint();
}
});
jf.setSize(800,800);
jf.setLocationRelativeTo(null);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.setVisible(true);
}
public static void main(String[] args){
new Test();
}
}

Answer 1

没看到你的绘制代码在哪里？
没有 drawXXX/fillXXX 

Answer 2

你试试下面代码看一下是否是你想要的效果import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
public class Test{
    private JButton jb=new JButton("按钮");
    private Point p=null;
    @SuppressWarnings("serial")
    public Test(){
        final JFrame jf=new JFrame(){
            @Override
            public void paint(Graphics g){
                super.paint(g);
                if(p!=null){
                    Graphics2D g2=(Graphics2D)g;
                    //下面是添加的代码
                    int x=(int)p.getX();
                    int y=(int)p.getY();
//                    g2.drawOval(x,y,10,10);
                    g2.fillOval(x,y,5,5);
                    jb.setLocation(p.x,p.y);
                }
            }
        };
        jb.setSize(64,30);
        jf.setLayout(null);
        jb.setVisible(false);
        jf.add(jb);
        jf.addMouseListener(new MouseAdapter(){
            @Override
            public void mouseClicked(MouseEvent e){
                if(p==null)
                    p=new Point();
                p=e.getPoint();
                jb.setVisible(true);
                jf.validate();
                jf.repaint();
            }
        });
        jf.setSize(800,800);
        jf.setLocationRelativeTo(null);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setVisible(true);
    }
    public static void main(String[] args){
        new Test();
    }
}