简易涂鸦板Java代码

以下是一个简易涂鸦板的 Java 代码示例：

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

public class DoodleBoard extends JFrame implements MouseListener, MouseMotionListener {
    private int lastX;
    private int lastY;
    private Color currentColor;
    private JPanel canvas;

    public DoodleBoard() {
        super("Doodle Board");
        setLayout(new BorderLayout());

        currentColor = Color.BLACK;

        canvas = new JPanel();
        canvas.setBackground(Color.WHITE);
        canvas.addMouseListener(this);
        canvas.addMouseMotionListener(this);
        add(canvas, BorderLayout.CENTER);

        JPanel colorPanel = new JPanel();
        colorPanel.setLayout(new GridLayout(1, 0));
        add(colorPanel, BorderLayout.SOUTH);

        JButton blackButton = new JButton("Black");
        blackButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                currentColor = Color.BLACK;
            }
        });
        colorPanel.add(blackButton);

        JButton redButton = new JButton("Red");
        redButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                currentColor = Color.RED;
            }
        });
        colorPanel.add(redButton);

        setSize(400, 400);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
    }

    public void mousePressed(MouseEvent e) {
        lastX = e.getX();
        lastY = e.getY();
    }

    public void mouseDragged(MouseEvent e) {
        Graphics g = canvas.getGraphics();
        g.setColor(currentColor);
        g.drawLine(lastX, lastY, e.getX(), e.getY());
        lastX = e.getX();
        lastY = e.getY();
    }

    public void mouseClicked(MouseEvent e) {}
    public void mouseEntered(MouseEvent e) {}
    public void mouseExited(MouseEvent e) {}
    public void mouseReleased(MouseEvent e) {}
    public void mouseMoved(MouseEvent e) {}

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

此代码创建了一个带有涂鸦板功能的窗口，用户可以在窗口中使用鼠标进行绘画。用户可以通过点击底部的按钮来选择颜色。涂鸦板使用 `JPanel` 组件作为画布，并在组件上使用 `MouseListener` 和 `MouseMotionListener` 来处理鼠标事件。在鼠标拖动期间，程序使用 `Graphics` 对象的 `drawLine` 方法来绘制线条。