java - BorderLayout 重复按钮

Question

我正在尝试创建一个可以在其中绘画的 Canvas ，以及一个将 Canvas 重置为空状态的按钮。然而，使用 BorderLayout 我的按钮会被复制，第二个按钮是第一个按钮的图像副本，但看起来仍然不太好。我的代码有什么问题吗？如何修复。

PaintCanvas.java

import javax.swing.* ;
import java.awt.*;
import java.awt.event.*;
import javax.swing.border.*;
class framakryesore extends JFrame {
    PaintCanvas p1 = new PaintCanvas();
    JButton b1 = new JButton ("Reset");
    public framakryesore (){


    b1.addActionListener(new ActionListener(){
        @Override
        public void actionPerformed(ActionEvent e){
            clearcanvas(p1);
            repaint();
        }
    });

    this.add(b1,BorderLayout.NORTH);            
    this.add(p1,BorderLayout.CENTER);




}
    public void clearcanvas(PaintCanvas p){
        p.setX(0);
        p.setY(0);
    }
}
public class PaintCanvas extends JPanel {
    private int x = 0 ;
    private int y = 0 ;
    public void  setX(int x){
        this.x = x;
    }
    public void setY(int y){
        this.y = y;
    }
    public PaintCanvas() {
    addMouseMotionListener(new MouseMotionListener() {
        @Override
        public void mouseDragged(MouseEvent e){
        x=e.getX();
        y=e.getY();
        repaint();
        }
        public void mouseMoved(MouseEvent e){

        }


    });

    }
    @Override
    protected void paintComponent (Graphics g){
        if (x==0 && y==0){
            super.paintComponent(g);
        }
        else
        {
        g.setFont(new Font("TimesRoman", Font.BOLD, 30)); 
        g.drawString(".", x, y);
        }

    }


}

PaintCanvasTest.java

import javax.swing.JFrame;


public class PaintCanvasTest {
 public static void main(String args[]){
     framakryesore pikturo = new framakryesore();
     pikturo.setVisible(true);
     pikturo.setSize(640, 480);
     pikturo.setTitle("Pikturo");
     pikturo.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


 }
}

Answer 1

if (x==0 && y==0){
    super.paintComponent(g);

您应该始终调用super.paintComponent()。它负责在进行自定义绘画之前清除面板的背景。