Linking HTML pages in Java

admin · Jan 10, 2008

I'm having difficulting getting my pages to linkin Java using the MouseListener interface. Here's the HTML: 
 
<HTML> 
<HEAD> 
<TITLE>Solid Signal</TITLE> 
</HEAD> 
<BODY leftmargin="120" bgcolor="#000000"> 
 
<IMG SRC=http://www.webdeveloper.com/forum/archive/index.php/solids.jpg WIDTH=700 HEIGHT=200> 
 
<APPLET code="EFields.class" width=700 height=300> 
 
< PARAM NAME=name1 VALUE="Transmissions" > 
< PARAM NAME=name2 VALUE="Codes" > 
< PARAM NAME=name3 VALUE="Signals" > 
< PARAM NAME=name4 VALUE="Contact" > 
 
< PARAM NAME=url1 VALUE="http://www.csc.liv.ac.uk/~frans/COMP101/AdditionalStuff/Applets/applets.html#introduction" > 
< PARAM NAME=url2 VALUE="http://www.csc.liv.ac.uk/~frans/COMP101/AdditionalStuff/Applets/applets.html#package" > 
< PARAM NAME=url3 VALUE="http://www.csc.liv.ac.uk/~frans/COMP101/AdditionalStuff/Applets/applets.html#example" > 
< PARAM NAME=url4 VALUE="http://www.detroittigers.com/index.html"> 
 
 
</APPLET> 
 
</MAP> 
</BODY> 
</HTML> 
 
And the Java code: 
... 
 
import java.applet.AppletContext; 
 
import java.awt.event.MouseListener; 
import java.awt.event.MouseEvent; 
 
import java.net.*; 
 
public class EFields extends JApplet implements MouseListener 
{ 
String[] urls = new String[4]; 
String[] names = new String[4]; 
String selectionName; 
... 
 
public void init() 
{ 
//URLs for links 
urls[0] = getParameter("url1"); 
urls[1] = getParameter("url2"); 
urls[2] = getParameter("url3"); 
urls[3] = getParameter("url4"); 
 
names[0] = getParameter("name1"); 
names[1] = getParameter("name2"); 
names[2] = getParameter("name3"); 
names[3] = getParameter("name4"); 
 
 
JPanel contentPane = new JPanel(); 
int frameSpeed=20; 
 
select1 = getAudioClip(getCodeBase(),"loop1.wav"); 
select2 = getAudioClip(getCodeBase(),"loop2.wav"); 
select3 = getAudioClip(getCodeBase(),"loop3.wav"); 
select4 = getAudioClip(getCodeBase(),"loop4.wav"); 
 
pic2=getImage(getCodeBase(),"trans.jpg"); 
pic3=getImage(getCodeBase(),"codes.jpg"); 
pic4=getImage(getCodeBase(),"signals.jpg"); 
pic5=getImage(getCodeBase(),"contact.jpg"); 
pic6=getImage(getCodeBase(),"trans2.jpg"); 
pic7=getImage(getCodeBase(),"codes2.jpg"); 
pic8=getImage(getCodeBase(),"signals2.jpg"); 
pic9=getImage(getCodeBase(),"contact2.jpg"); 
... 
selectAreas= new UseArea(Color.black); 
 
contentPane.add(selectAreas); 
selectAreas.addMouseListener(this); 
 
addMouseListener(this); 
setContentPane(contentPane); 
... 
 
public void mouseClicked(MouseEvent e) 
{ 
// Get url and try to connect 
for (int index=0;index < names.length;index++) 
{ 
if (selectionName.equals(names[index])) 
{ 
try 
{ 
URL site = new URL(urls[index]); 
AppletContext context = getAppletContext(); 
context.showDocument(site); 
} 
 
catch (MalformedURLException m) 
{ 
System.exit(1); 
} 
 
return; 
} 
} 
 
} 
... 
} 
 
I edited some stuff out. It compiles without any errors or warnings, but when I run it I get a null pointer exception at the line containing: 
 
if (selectionName.equals(names[index])) 
 
Any ideas on how to fix this? I've spent hours trying to get it to work and I've looked at many demos online. I've tried to compile and run them and I get the same results. Also, most use buttons (ActionListener) instead of the mouse. 
 
Thanks! 
 
Ryanyou need to post this in te Java forum

Linking HTML pages in Java

admin

Administrator