ch7_e7_20.java

代码包括《Java语言与面向对象程序设计题解与实验指导》一书中 “习题解答”部分的所有程序的Java源代码和编译后生成的字节码或相应的HTML文件。 盘中的目录与书中的章节一致。

import java.applet.Applet; 
import java.awt.*;
import java.awt.event.*;

public class ch7_e7_20 extends Applet implements 
    MouseListener, MouseMotionListener
{
    int beginX=0, beginY=0, endX=0, endY=0;
    public void init()
    {
        this.addMouseListener(this);
        this.addMouseMotionListener(this);
    }
    public void paint(Graphics g)
    {
        int x1,x2,y1,y2;
        
        if(beginX < endX)
        {
            x1 = beginX;
            x2 = endX;
        }
        else
        {
            x1 = endX;
            x2 = beginX;
        }
        if(beginY < endY)
        {
            y1 = beginY;
            y2 = endY;
        }
        else
        {
            y1 = endY;
            y2 = beginY;
        }
        g.drawRect(x1,y1,x2-x1,y2-y1);
    }
        
    public void mouseClicked(MouseEvent me)
    {
    }    
    public void mouseEntered(MouseEvent me)
    {
    }
    public void mouseExited(MouseEvent me)
    {
    }
    public void mousePressed(MouseEvent me)
    {
        beginX = endX = me.getX();
        beginY = endY = me.getY();   
    }
    public void mouseReleased(MouseEvent me)
    {
    }
    public void mouseMoved(MouseEvent me)
    {
        showStatus("(" + me.getX() + "," + me.getY() + ")");
    }
    public void mouseDragged(MouseEvent me)
    {
        endX = me.getX();
        endY = me.getY();
        showStatus("(" + endX + "," + endY + ")");
        repaint();
    }
}