Swing 100行画图示例

关键内容,可以自行扩展

package main;

import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Point2D;
import java.util.Vector;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;

public class MainFrame extends JFrame implements MouseListener, MouseMotionListener {
	/**
	 *
	 */
	private static final long serialVersionUID = 1L;
	private JPanel contentPane;
	private Graphics2D g2;
	private static Vector<Point2D> pointInfo;
	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		SwingUtilities.invokeLater(() -> {
			MainFrame mainFrame = new MainFrame();
			mainFrame.setLocationRelativeTo(null);
			mainFrame.setVisible(true);
		});
	}
	/**
	 * Create the frame.
	 */
	public MainFrame() {
		addMouseListener(this);
		addMouseMotionListener(this);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 951, 606);
		contentPane = new JPanel();
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		contentPane.setLayout(new BorderLayout(0, 0));
		setContentPane(contentPane);
		//初始化
		pointInfo=new Vector<>();
	}
	@Override
	public void paint(Graphics g) {
		System.out.println("paint");
		 g2 = (Graphics2D) g;
		 int size = pointInfo.size();
		 Point p1,p2;
		 g2.setColor(Color.BLACK);
		 g2.setStroke(new BasicStroke(WIDTH));
		 for (int i = 0; i < size-1; i++) {
			 p1 = (Point) pointInfo.elementAt(i);
			 p2 = (Point) pointInfo.elementAt(i + 1);
			 g2.drawLine(p1.x, p1.y, p2.x, p2.y);
		}
	}
	public void update(Graphics g) {
		System.out.println("update");
		paint(g);
	}
	@Override
	public void mouseDragged(MouseEvent e) {
		System.out.println("mouseDragged");
		Point cutflag = new Point(e.getX(), e.getY());
		pointInfo.addElement(cutflag);
		repaint();
	}
	@Override
	public void mousePressed(MouseEvent e) {
		Point cutflag = new Point(e.getX(), e.getY());
		pointInfo.addElement(cutflag);
	}
	@Override
	public void mouseReleased(MouseEvent e) {
		Point cutflag = new Point(-1, -1);
		pointInfo.addElement(cutflag);
		pointInfo.clear();
	}
	@Override
	public void mouseMoved(MouseEvent e) {
	}
	@Override
	public void mouseClicked(MouseEvent e) {
	}
	@Override
	public void mouseEntered(MouseEvent e) {
	}

	@Override
	public void mouseExited(MouseEvent e) {
	}
}