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) {
  }
}