java作业——用鼠标画曲线

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

@SuppressWarnings("serial")
public class PaintLineJFrame extends JFrame{
	
	public PaintLineJFrame() {
		// TODO Auto-generated constructor stub
		super("用鼠标画曲线");
		this.setBounds(400, 300, 400, 300);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.getContentPane().add(new PaintLineCanvas());
		this.setVisible(true);
	}
	
	class PaintLineCanvas extends Canvas implements MouseListener ,MouseMotionListener{
		
		Point start, end;
		
		public PaintLineCanvas() {
			start = end = null;
			this.addMouseListener(this);
			this.addMouseMotionListener(this);
		}
		
		public void paint(Graphics g) {
			g.setColor(Color.blue);
			g.drawLine(start.x, start.y, end.x, end.y);
		}
		
		public void update(Graphics g) {
			this.print(g);
			
		}

		@Override
		public void mouseClicked(MouseEvent e) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public void mousePressed(MouseEvent e) {
			// TODO Auto-generated method stub
			start = new Point(e.getX(), e.getY());
		}

		@Override
		public void mouseReleased(MouseEvent e) {
			// TODO Auto-generated method stub
			end = null;
		}

		@Override
		public void mouseEntered(MouseEvent e) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public void mouseExited(MouseEvent e) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public void mouseDragged(MouseEvent e) {
			// TODO Auto-generated method stub
			if (end != null) {
				start = end;
			}
			end = new Point(e.getX(), e.getY());
			repaint();
		}

		
		@Override
		public void mouseMoved(MouseEvent e) {
			// TODO Auto-generated method stub
		}
	}
	

	public static void main(String[] args) {
		new PaintLineJFrame();
	}
	
}