Java实现白板程序的代码

以下是一个简单的Java白板程序的代码示例：

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

public class Whiteboard extends JFrame {

    private JPanel canvas;
    private int startX, startY, endX, endY;
    private Color currentColor;
    private int currentSize;

    public Whiteboard() {
        setTitle("Whiteboard");
        setSize(800, 600);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        canvas = new JPanel();
        canvas.setBackground(Color.WHITE);
        canvas.addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                startX = e.getX();
                startY = e.getY();
            }
        });
        canvas.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseDragged(MouseEvent e) {
                endX = e.getX();
                endY = e.getY();
                Graphics2D g = (Graphics2D) canvas.getGraphics();
                g.setColor(currentColor);
                g.setStroke(new BasicStroke(currentSize));
                g.drawLine(startX, startY, endX, endY);
                startX = endX;
                startY = endY;
            }
        });
        add(canvas, BorderLayout.CENTER);

        JMenuBar menuBar = new JMenuBar();
        JMenu fileMenu = new JMenu("File");
        JMenuItem saveItem = new JMenuItem("Save");
        JMenuItem openItem = new JMenuItem("Open");
        saveItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                // Implement save functionality here
            }
        });
        openItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                // Implement open functionality here
            }
        });
        fileMenu.add(saveItem);
        fileMenu.add(openItem);
        menuBar.add(fileMenu);
        setJMenuBar(menuBar);

        JToolBar toolBar = new JToolBar();
        JButton pencilButton = new JButton(new ImageIcon("pencil.png"));
        pencilButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                currentColor = Color.BLACK;
                currentSize = 2;
            }
        });
        JButton lineButton = new JButton(new ImageIcon("line.png"));
        lineButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                currentColor = Color.RED;
                currentSize = 4;
            }
        });
        toolBar.add(pencilButton);
        toolBar.add(lineButton);
        add(toolBar, BorderLayout.NORTH);
    }

    public static void main(String[] args) {
        Whiteboard whiteboard = new Whiteboard();
        whiteboard.setVisible(true);
    }
}

这个代码示例创建了一个带有绘图面板、菜单和工具栏的Java白板程序。它使用了Java的Swing库来创建GUI组件和事件监听器，并使用了Graphics2D类来绘制基本形状。你可以根据自己的需求对代码进行修改和扩展。