如何删除矩形？

Question

我需要一些Java代码的帮助。我的代码允许矩形跟随鼠标图标的确切位置，但我想让矩形停在我用鼠标点击绘图面板的位置。如何实现这一目标？谁能帮我？

这是我的代码：

图纸

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.event.*;

public class Drawing extends JFrame
{
    public Drawing()
    {}

    public static void main(String[] args)
    {
        Panel p = new Panel();
        p.setBackground(Color.white);
        JFrame f = new JFrame();
        f.setSize(800, 500);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(p);
        f.setVisible(true);
        f.setLocationRelativeTo(null);
    }
}

面板

public class Panel extends JPanel implements  MouseMotionListener
    {   
        int x=0;
        int y=0;
        int width=200;
        int height=200;

        public Panel()
        {
            addMouseMotionListener(this);       
        }

        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            g.setColor(Color.red);
            g.fillRect(x, y, width, height);
        }

        public void mousePressed(MouseEvent e){}
        public void mouseDragged(MouseEvent e){}    
        public void mouseMoved(MouseEvent e)
        {
            x = e.getX() - 75;
            y = e.getY() -75;
            repaint();
        }
        public void mouseEntered(MouseEvent e){}
        public void mouseClicked(MouseEvent e){}
        public void mouseReleased(MouseEvent e){}
        public void mouseExited(MouseEvent e){}
    }

Answer 1

你的类Panel应该实现MouseListener接口并调用addMouseListener方法才能使用mousePressed方法;要停止移动面板，请使用布尔值，当您按下鼠标按钮时更改状态，将面板类更改为以下代码：

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

import javax.swing.JPanel;

public class Panel extends JPanel implements MouseMotionListener, MouseListener {
    int x = 0;
    int y = 0;
    int width = 200;
    int height = 200;
    boolean move = true;

    public Panel() {
        addMouseMotionListener(this);
        addMouseListener(this);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (move) {
            g.setColor(Color.red);
            g.fillRect(x, y, width, height);
        }
    }

    public void mousePressed(MouseEvent e) {
        move = !move;
    }

    public void mouseDragged(MouseEvent e) {
    }

    public void mouseMoved(MouseEvent e) {
        if (move) {
            x = e.getX() - 75;
            y = e.getY() - 75;
            repaint();
        }
    }

    public void mouseEntered(MouseEvent e) {
    }

    public void mouseClicked(MouseEvent e) {
    }

    public void mouseReleased(MouseEvent e) {
    }

    public void mouseExited(MouseEvent e) {
    }
}