Java是一種流行的編程語言，廣泛應用于開發各種應用程序。其中，Java的繪圖功能非常強大，可以通過菜單和按鈕控制繪圖，實現各種效果。下面我們來介紹一下如何使用Java用菜單和按鈕控制繪圖。

首先，我們需要創建一個窗口，通過窗口展示我們的繪圖。代碼如下：

import javax.swing.*;
import java.awt.*;
public class DrawFrame extends JFrame {
public DrawFrame() {
setTitle("Java繪圖");
setSize(400, 300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
setLocationRelativeTo(null);
}
public static void main(String[] args) {
new DrawFrame();
}
}

在創建完窗口之后，我們需要在窗口中添加菜單和按鈕，用于控制繪圖。代碼如下：

import javax.swing.*;
import java.awt.*;
public class DrawFrame extends JFrame {
private JMenuBar menuBar;
private JMenu fileMenu;
private JMenuItem newMenuItem;
private JMenuItem quitMenuItem;
private JPanel buttonPanel;
private JButton drawButton;
private JButton clearButton;
private DrawPanel drawPanel;
public DrawFrame() {
setTitle("Java繪圖");
setSize(400, 300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
menuBar = new JMenuBar();
fileMenu = new JMenu("File");
newMenuItem = new JMenuItem("New");
newMenuItem.addActionListener(event ->drawPanel.clear());
quitMenuItem = new JMenuItem("Quit");
quitMenuItem.addActionListener(event ->System.exit(0));
fileMenu.add(newMenuItem);
fileMenu.addSeparator();
fileMenu.add(quitMenuItem);
menuBar.add(fileMenu);
setJMenuBar(menuBar);
drawPanel = new DrawPanel();
buttonPanel = new JPanel();
drawButton = new JButton("Draw");
drawButton.addActionListener(event ->drawPanel.draw());
clearButton = new JButton("Clear");
clearButton.addActionListener(event ->drawPanel.clear());
buttonPanel.add(drawButton);
buttonPanel.add(clearButton);
add(buttonPanel, BorderLayout.NORTH);
add(drawPanel, BorderLayout.CENTER);
setVisible(true);
}
public static void main(String[] args) {
new DrawFrame();
}
}

在菜單和按鈕的代碼中，我們定義了一個DrawPanel類，用于繪圖。它包含draw()方法和clear()方法，分別用于繪圖和清空。下面是DrawPanel的代碼：

import javax.swing.*;
import java.awt.*;
public class DrawPanel extends JPanel {
private static final int WIDTH = 300;
private static final int HEIGHT = 200;
private boolean isDrawing;
private int x1, y1, x2, y2;
public DrawPanel() {
setPreferredSize(new Dimension(WIDTH, HEIGHT));
setBackground(Color.WHITE);
addMouseListener(new MouseHandler());
addMouseMotionListener(new MouseMotionHandler());
}
public void draw() {
isDrawing = true;
repaint();
}
public void clear() {
isDrawing = false;
repaint();
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
if (isDrawing) {
g.drawLine(x1, y1, x2, y2);
}
}
private class MouseHandler extends MouseAdapter {
@Override
public void mousePressed(MouseEvent event) {
x1 = event.getX();
y1 = event.getY();
}
@Override
public void mouseReleased(MouseEvent event) {
x2 = event.getX();
y2 = event.getY();
isDrawing = false;
repaint();
}
}
private class MouseMotionHandler extends MouseMotionAdapter {
@Override
public void mouseDragged(MouseEvent event) {
x2 = event.getX();
y2 = event.getY();
isDrawing = true;
repaint();
}
}
}

最后，我們來看看效果。運行程序，點擊Draw按鈕后，可以使用鼠標在繪圖區域內繪制直線。點擊Clear按鈕后，可以清空繪圖區域。