paint1.java

实现画直线功能

import java.awt.*;
import java.awt.event.*;

public class Paint1 extends Frame implements MouseListener, MouseMotionListener
{
    int oldX = -1, oldY = -1;
	public static void main(String[] args) 
	{
                new Paint1();
	}
    public Paint1() {
        setBackground(Color.blue);
        setForeground(Color.yellow);
        addMouseListener(this);
        addMouseMotionListener(this);
        setSize(400,300);
        setVisible(true);
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent we) {
                System.exit(0); }});
    }

    public void mouseClicked(MouseEvent me) {}
    public void mouseEntered(MouseEvent me) {}
    public void mouseExited(MouseEvent me) {}
    public void mousePressed(MouseEvent me) {}
    public void mouseReleased(MouseEvent me) {
        oldX = -1; 
    }
    public void mouseMoved(MouseEvent me) {}
    public void mouseDragged(MouseEvent me) {
        int x = me.getX();  
        int y = me.getY();
        if (oldX == -1)
        {
            oldX = x;   oldY = y;
            return;
        }
        Graphics g = getGraphics();
        g.drawLine(oldX, oldY, x, y);
        oldX = x;   oldY = y;
    }

}