Java Graphics - 像Zelle's Graphics for Python这样简单的东西

 Java类Graphics和Graphics2D应该包含Zelle图形所包含的大部分内容。

下面是一些Java Swing代码，让您开始学习。只要你按住鼠标左键，这个Java应用程序就会用鼠标绘制。当你释放鼠标左键时，屏幕会擦除，你可以画其他东西。

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.event.MouseInputAdapter;
public class DrawingTest implements Runnable {
    private JFrame frame;
    private MyDrawPanel drawPanel;
    private List<Point> points;
    public DrawingTest() {
        points = new ArrayList<Point>();
    }
    @Override
    public void run() {
        frame = new JFrame("Bouncing Vertices");
        drawPanel = new MyDrawPanel(this);
        MyListener alpha = new MyListener(this);
        drawPanel.addMouseMotionListener(alpha);
        drawPanel.addMouseListener(alpha);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(drawPanel);
        frame.setSize(800, 600);
        frame.setVisible(true);
    }
    public JPanel getDrawingPanel() {
        return drawPanel;
    }
    public List<Point> getPoints() {
        return points;
    }
    public void setPoint(int x, int y) {
        points.add(new Point(x, y));
    }
    public void resetPoints() {
        points.clear();
    }
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new DrawingTest());
    }
    private class MyListener extends MouseInputAdapter {
        private DrawingTest drawingTest;
        public MyListener(DrawingTest drawingTest) {
            this.drawingTest = drawingTest;
        }
        @Override
        public void mouseDragged(MouseEvent event) {
            drawingTest.setPoint(event.getX(), event.getY());
            drawingTest.getDrawingPanel().repaint();
        }
        @Override
        public void mouseReleased(MouseEvent event) {
            drawingTest.resetPoints();
        }
    }
    private class MyDrawPanel extends JPanel {
        private static final long serialVersionUID = 1L;
        private DrawingTest drawingTest;
        public MyDrawPanel(DrawingTest drawingTest) {
            this.drawingTest = drawingTest;
        }
        @Override
        public void paintComponent(Graphics g) {
            g.setColor(Color.WHITE);
            g.fillRect(0, 0, this.getWidth(), this.getHeight());
            g.setColor(Color.BLUE);
            for (int i = 1; i < drawingTest.getPoints().size(); i++) {
                Point p1 = drawingTest.getPoints().get(i - 1);
                Point p2 = drawingTest.getPoints().get(i);
                g.drawLine(p1.x, p1.y, p2.x, p2.y);
            }
        }
    }
}

代码中的最后一个方法paintComponent方法是使用Graphics方法的地方。