java - 如何在java中删除画线？

Question

问题是如何删除旧行？我的意思是，只让当前的 x 和 y 线出现在屏幕上，让两条线之间的交点“跟随”鼠标指针。

这是更新后的代码:

import javax.swing.*;
import javax.*;
import java.awt.*;
import java.awt.Color;
import java.awt.Graphics.*;
import java.awt.event.*;
import javax.swing.UIManager;
public class SimpleGUI extends JFrame {
    public SimpleGUI() {
           this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ;
    }

    public void go() {
        Drawpanel = new Mypanel();
        JFrame frame = new JFrame("Chasing Line");
        JButton mybutton1 = new JButton("Please");
        JButton mybutton2 = new JButton("Help");
        JButton mybutton3 = new JButton("Me!!");
        Drawpanel.add(mybutton1); 
        Drawpanel.add(mybutton2);
        Drawpanel.add(mybutton3);

        frame.getContentPane().add(BorderLayout.CENTER, Drawpanel);
        frame.setSize(300,300);
        frame.setVisible(true);

        Drawpanel.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() {
            public void mouseMoved(java.awt.event.MouseEvent evt) {
                DrawpanelMouseMoved(evt);
            }
        }); 

    }

    public void DrawpanelMouseMoved(java.awt.event.MouseEvent evt) {
        xpos=evt.getX();
        ypos=evt.getY();
        System.out.println("Coordinates : X :"+ xpos+"Y: "+ypos);
        Drawpanel.paintImage(xpos,ypos);
    } 

    class Mypanel extends JPanel {
        public void paintImage(int xpost,int ypost){
            Graphics d = getGraphics();
            d.clearRect(0,0, this.getWidth(), this.getHeight());
            d.setColor(Color.black);
            d.drawLine(xpost, 0, xpost, this.getHeight());
            d.setColor(Color.red);
            d.drawLine(0, ypost, this.getWidth(),ypost);
            this.validate();
        }

    } // end the inner class 

    public static void main(String[] args){
        try {
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } catch(Exception e) {
            System.err.println("Look and feel not set");
        }

        SimpleGUI win = new SimpleGUI();
        win.go();
    }

    Mypanel Drawpanel;
    private int xpos=0;
    private int ypos=0;
}  // close SimpleGUI class

问题是如何在不改变状态的情况下保留这 3 个按钮？

Answer 1

The problem is how can i delete the old lines?, i mea,make only the current x and y lines appear on the screen, make the intersection between both lines "follow" the mouse pointer.

• 将所有要保留的行保存在 LinkedList 或类似列表中。
• 重新开始绘制背景，这将清除您的旧线条。
• 在 LinkedList 中绘制所有行。

或者如果您不想保存任何行:

1. 再次绘制背景，这将删除旧线条。
2. 画出你的线条。

你可以再次绘制背景:

clearRect(int x, int y, int width, int height)