paintline.java

画图

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

class  MousePaint extends JPanel
{
	int startX,startY;
	int endX,endY;
	ArrayList list,Array;
	public MousePaint()
	{
  	list=new ArrayList();
  	Array=new ArrayList();

		addMouseListener(new MouseAdapter()
  	{
   		public void mousePressed(MouseEvent e)
   		{
    		startX=e.getX();
    		startY=e.getY();
   		}
   		public void mouseReleased(MouseEvent e)
   		{
    		MyLine my=new MyLine(startX,startY,e.getX(),e.getY());
    		Array.add(my);
    		repaint();
   		}
  	});
	
	  addMouseMotionListener(new MouseMotionAdapter()
  	{
   		public void mouseDragged(MouseEvent e)
   		{
    		endX = e.getX();
        endY = e.getY();
    		repaint();
   		}
  	});
	}

	public void paintComponent(Graphics g)
	{
  	super.paintComponent(g);
  	Iterator it=Array.iterator();
  	while(it.hasNext())
  	{
   		MyLine line=(MyLine)it.next();
   		line.drawMe(g);
  	}
  	g.drawLine(startX,startY,endX,endY);
	}

	public static void main(String[] args) 
	{
		JFrame jf=new JFrame();
		jf.getContentPane().add(new MousePaint(),BorderLayout.CENTER);
		jf.setBounds(300,300,400,400);
		jf.setVisible(true);
		jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
}

class MyLine
{
	private int startX,startY;
	private int endX,endY;
	public MyLine(int startX,int startY,int endX,int endY)
	{
  	this.startX = startX;
  	this.startY = startY;
  	this.endX = endX;
  	this.endY = endY;
	}
	
	public void drawMe(Graphics g)
	{
  	g.setColor(Color.black);
  	g.drawLine(startX,startY,endX,endY);
	}
};