java Gui徒手绘画

Java GUI（图形用户界面）可以使用Java Swing库进行开发，绘画可以使用Java Graphics2D类。下面是一个简单的Java GUI程序，该程序提供了一个绘画区和一些工具，可以选择画笔颜色和笔刷大小，还有橡皮擦工具。

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

public class DrawingApp extends JFrame {
    private JPanel canvas;
    private JComboBox<String> colorChooser;
    private JComboBox<Integer> sizeChooser;
    private JToggleButton eraseButton;

    private Color currentColor = Color.black;
    private int currentSize = 5;

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

    public DrawingApp() {
        setTitle("Drawing App");
        setSize(800, 600);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // create canvas panel and add to frame
        canvas = new JPanel();
        canvas.setBackground(Color.white);
        canvas.addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                Graphics2D g = (Graphics2D) canvas.getGraphics();
                g.setColor(currentColor);
                if (eraseButton.isSelected()) {
                    g.setColor(canvas.getBackground());
                }
                g.setStroke(new BasicStroke(currentSize,
                        BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));
                g.drawLine(e.getX(), e.getY(), e.getX(), e.getY());
            }
        });
        canvas.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseDragged(MouseEvent e) {
                Graphics2D g = (Graphics2D) canvas.getGraphics();
                g.setColor(currentColor);
                if (eraseButton.isSelected()) {
                    g.setColor(canvas.getBackground());
                }
                g.setStroke(new BasicStroke(currentSize,
                        BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));
                g.drawLine(e.getX(), e.getY(), e.getX(), e.getY());
            }
        });
        add(canvas, BorderLayout.CENTER);

        // create tool panel and add to frame
        JPanel toolPanel = new JPanel();
        add(toolPanel, BorderLayout.NORTH);

        colorChooser = new JComboBox<String>(new String[] {"Black", "Red", "Green", "Blue"});
        colorChooser.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String color = (String) colorChooser.getSelectedItem();
                switch (color) {
                    case "Black":
                        currentColor = Color.black;
                        break;
                    case "Red":
                        currentColor = Color.red;
                        break;
                    case "Green":
                        currentColor = Color.green;
                        break;
                    case "Blue":
                        currentColor = Color.blue;
                        break;
                }
            }
        });
        toolPanel.add(new JLabel("Color:"));
        toolPanel.add(colorChooser);

        sizeChooser = new JComboBox<Integer>(new Integer[] {1, 3, 5, 10});
        sizeChooser.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                currentSize = (Integer) sizeChooser.getSelectedItem();
            }
        });
        toolPanel.add(new JLabel("Size:"));
        toolPanel.add(sizeChooser);

        eraseButton = new JToggleButton("Eraser");
        toolPanel.add(eraseButton);
    }
}

该程序创建了一个JFrame窗口，并在其中添加了一个绘画区（JPanel）和一个工具区（JPanel）。绘画区使用MouseListener和MouseMotionListener监听鼠标事件，并使用Graphics2D类绘制图形。工具区提供了选择颜色、笔刷大小和橡皮擦工具的选项。