java绘图的一个小问题

[开不了口1990]

想用鼠标画个点，可以坐标总是不对，不知道要怎么改。

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

public class DrawTest extends JFrame {
	MyPanel mp = null;

	public static void main(String[] args) {
		new DrawTest();
	}

	public DrawTest() {
		mp = new MyPanel();
		this.addMouseListener(mp);
		this.add(mp);
		this.setSize(600, 400);
		this.setLocation(400, 300);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		this.setVisible(true);
	}
}

class MyPanel extends JPanel implements MouseListener {
	int x = 0, y = 0;
	Image img = null;

	public void paint(Graphics g) {
		super.paint(g);
		g.fillOval(x, y, 10, 10);
	}

	public void mouseClicked(MouseEvent e) {
		x = e.getX();
		y = e.getY();
		this.repaint();
	}

	public void mousePressed(MouseEvent e) {
	}

	public void mouseReleased(MouseEvent e) {
	}

	public void mouseEntered(MouseEvent e) {
	}

	public void mouseExited(MouseEvent e) {
	}

}

[liuwons]

我能想到的原因：点击事件获取的鼠标xy坐标是相对于程序界面左上角的，而画图的fillOval的xy是相对于工作区左上角的，所以会相差一个边框的高度和宽度

[Inhibitory]

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

public class DrawTest extends JFrame {
    MyPanel mp = null;

    public static void main(String[] args) {
        new DrawTest();
    }

    public DrawTest() {
        mp = new MyPanel();

        // 鼠标事件是加在frame上，而不是在mp上的，
        // 所以在mp中取得坐标时，坐标不是相对于mp的，而是相对于frame的
        // 而frame还有一个标题栏，这个是有高度的
        // 最终使用屏幕坐标转换成组件坐标可以解决这一问题
        this.addMouseListener(mp);

        this.add(mp);
        this.setSize(600, 400);
        this.setLocationRelativeTo(null);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
    }
}

class MyPanel extends JPanel implements MouseListener {
    int x = 0, y = 0;
    Image img = null;

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.fillOval(x, y, 10, 10);
    }

    public void mouseClicked(MouseEvent e) {
        Point p = e.getLocationOnScreen();
        SwingUtilities.convertPointFromScreen(p, this); // 关键在于把屏幕坐标映射成组件坐标
        x = p.x;
        y = p.y;
        this.repaint();
    }

    public void mousePressed(MouseEvent e) {
    }

    public void mouseReleased(MouseEvent e) {
    }

    public void mouseEntered(MouseEvent e) {
    }

    public void mouseExited(MouseEvent e) {
    }

}

[开不了口1990]

谢谢了！[Quote=引用 2 楼 的回复:]
Java code
import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

public class DrawTest extends JFrame {
MyPanel mp = null;

public st……
[/Quote]