在JLabel上绘制-更改画笔颜色

import javax.swing.*;
import java.awt.*;

public class DrawOnJLabel extends JLabel {
    private Color penColor;

    public DrawOnJLabel() {
        penColor = Color.BLACK;
    }

    public void setPenColor(Color color) {
        penColor = color;
        repaint(); // 重新绘制JLabel
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        // 设置画笔颜色
        g.setColor(penColor);

        // 绘制图形
        g.drawLine(0, 0, getWidth(), getHeight());
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Draw on JLabel");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        DrawOnJLabel label = new DrawOnJLabel();
        frame.add(label);

        JButton redButton = new JButton("Red");
        redButton.addActionListener(e -> label.setPenColor(Color.RED));

        JButton blueButton = new JButton("Blue");
        blueButton.addActionListener(e -> label.setPenColor(Color.BLUE));

        JPanel buttonPanel = new JPanel();
        buttonPanel.add(redButton);
        buttonPanel.add(blueButton);
        frame.add(buttonPanel, BorderLayout.SOUTH);

        frame.setSize(400, 300);
        frame.setVisible(true);
    }
}