问题2

Question

import java.applet.*;
import java.awt.*;
public class ShowAnimator extends Applet //shows Exception
{
    Image [] m_Images;
    int totalImages=14;
    int currentImage=0;
    public void init()
    {
        m_Images=new Image[totalImages];
        for(int i=0;i<totalImages;i++)
        {
            m_Images[i]=getImage(getCodeBase(),"images\\img00"+(i+1)+".gif");
        }
    }
    public void start()
    {
        currentImage=0;
    }
    public void paint(Graphics g)
    {
        g.drawImage(m_Images[currentImage],50,50,this);
        currentImage=++currentImage%totalImages;
        try
        {
            Thread.sleep(50);
        }
        catch(Exception e)
        {
        }
        repaint();
    }
    public static void main(String [] args)
    {
        Frame f=new Frame("DrawImages");
        ShowAnimator s=new ShowAnimator();
        f.add(s);
        s.init();
        f.setSize(200,100);
        f.setVisible(true);
    }        
}//<applet code="ShowAnimator.class" width=300 height=300>
//</applet>错误提示如下：
D:\java\lesson6>java ShowAnimator
Exception in thread "main" java.lang.NullPointerException
        at java.applet.Applet.getCodeBase(Unknown Source)
        at ShowAnimator.init(ShowAnimator.java:13)
        at ShowAnimator.main(ShowAnimator.java:38)

Answer 1

m_Images[i]=getImage(getCodeBase(),"images\\img00"+(i+1)+".gif");这句好像没有获得图片，"images\\img00" 这样写感觉不太对
 
f.add(s);  // Frame默认布局为BorderLayout, 改为f.add(s,"Cneter");