List and Font

[lianergoist]

I have a problem with Font in a list. To me it looks like a bug in the java libraries, but I'm a newbee, so maybe it's just me not understanding it.

I can change the font size in my list. But if I add elements to the list, it throws an ArrayIndexOutOfBoundsException. Take a look at the rebuild command in the code. I have tried a lot of things to get around it, including deleting all the elements and loading them again, but with no luck.

The error says:

java.lang.ArrayIndexOutOfBoundsException
at javax.microedition.lcdui.ChoiceGroup.insertImpl(ChoiceGroup.java:1420)
at javax.microedition.lcdui.ChoiceGroup.append(ChoiceGroup.java:397)
at javax.microedition.lcdui.List.append(List.java:429)
at listtest.commandAction(listtest.java:70)
at javax.microedition.lcdui.Display$DisplayAccessor.commandAction(Display.java:2093)
at javax.microedition.lcdui.Display$DisplayManagerImpl.commandAction(Display.java:2929)
at com.sun.midp.lcdui.DefaultEventHandler.commandEvent(DefaultEventHandler.java:297)
at com.sun.midp.lcdui.AutomatedEventHandler.commandEvent(AutomatedEventHandler.java:667)
at com.sun.midp.lcdui.DefaultEventHandler$QueuedEventHandler.handleVmEvent(DefaultEventHandler.java:711)
at com.sun.midp.lcdui.DefaultEventHandler$QueuedEventHandler.run(DefaultEventHandler.java:608)


Any ideas what is wrong and how to get around it? Do I really have to delete the list and create a new one?

import java.util.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;

public class listtest extends MIDlet implements CommandListener {
    private Display display;
    private List list;
    private Command exitcmd, reloadcmd;
    private Vector v;
    Font f;

    public void startApp() {

        reloadcmd = new Command("Reload", Command.SCREEN, 1);
        exitcmd = new Command("Exit", Command.EXIT, 2);

        f = Font.getFont(0, 0, Font.SIZE_LARGE);

        v = new Vector(1,1);
        v.addElement("string1");
        v.addElement("string2");
        v.addElement("string3");
        v.addElement("string4");

        list = new List("", Choice.IMPLICIT);
        list.addCommand(reloadcmd);
        list.addCommand(exitcmd);
        list.setCommandListener(this);

        int i = 0;
        for (Enumeration e = v.elements(); e.hasMoreElements(); i++ ) {
            list.append((String)e.nextElement(), null);
            // ArrayIndexOutOfBoundsException, if setting font here...
            // list.setFont(i, f);
        }

        for (i=1 ; i<list.size() ; i++ ) {
            // It's okay here...
            list.setFont(i, f);
        }

        display = Display.getDisplay(this);
        display.setCurrent(list);
    }

    public void pauseApp() {
    }

    public void destroyApp(boolean unconditional) {
    }

    public void commandAction (Command c, Displayable d) {
        if (c == reloadcmd) {


//            list.deleteAll();
//            int i = 0;
//            for (Enumeration e = v.elements(); e.hasMoreElements(); i++ ) {
//                list.append((String)e.nextElement(), null);
//            }

            list.append("test", null);
        
//            for (i=0 ; i<list.size() ; i++ ) {
//                if (!list.getFont(i).equals(f)){
//                    list.setFont(i, f);
//                }
//            }

            display.setCurrent(list);
        
        }
        
        if (c == exitcmd) {
            destroyApp(true);
            notifyDestroyed();
        }
    }
}

[r2j7]

Hello lianergoist,

could you specify please which Nokia device or SDK emulator results in the Exception?

Regards,
r2j7

[raj_J2ME]

I suspect about your font, try to give some face and style too while you are creating the same. Then you go for testing it.

[lianergoist]

I suspect about your font, try to give some face and style too while you are creating the same. Then you go for testing it.

Like this?

f = Font.getFont(Font.FACE_SYSTEM , Font.STYLE_PLAIN, Font.SIZE_LARGE);

Well, it didn't change anything - and it shouldn't. The API reference says:

The values of these constants are arranged so that zero is valid for each attribute and can be used to specify a reasonable default font for the system. For clarity of programming, the following symbolic constants are provided and are defined to have values of zero:

* STYLE_PLAIN
* SIZE_MEDIUM
* FACE_SYSTEM

But thanks for the suggestion...

[lianergoist]

Hello lianergoist,

could you specify please which Nokia device or SDK emulator results in the Exception?

Regards,
r2j7

Well, the error output posted earlier was from Netbeans6.9 using WTK2.5.2 and DefaultColorPhone profile. Building and running the program from ktoolbar give this error:

java.lang.ArrayIndexOutOfBoundsException
at javax.microedition.lcdui.ChoiceGroup.insertImpl(+456)
at javax.microedition.lcdui.ChoiceGroup.append(+25)
at javax.microedition.lcdui.List.append(+9)
at listtest.commandAction(+71)
at javax.microedition.lcdui.Display$DisplayAccessor.commandAction(+282)
at javax.microedition.lcdui.Display$DisplayManagerImpl.commandAction(+10)
at com.sun.midp.lcdui.DefaultEventHandler.commandEvent(+68)
at com.sun.midp.lcdui.AutomatedEventHandler.commandEvent(+47)
at com.sun.midp.lcdui.DefaultEventHandler$QueuedEventHandler.handleVmEvent(+186)
at com.sun.midp.lcdui.DefaultEventHandler$QueuedEventHandler.run(+57)

When running the program on my Samsung B2100 phone, I get no errors, but the new line is not appended (list.append("test", null) and the 4 elements are all with standard size (not large, as 3 of them were before running the rebuild command).

[Tiger79]

Maybe you might want to do some System.out.println within your :

for (i=1 ; i<list.size() ; i++ ) {
// It's okay here...
list.setFont(i, f);
}

just to check where it al goes wrong ?
Also shouldn't the variable i be initialised with 0 ?

Personally looking at your error I think something is going wrong here :

for (Enumeration e = v.elements(); e.hasMoreElements(); i++ ) {
list.append((String)e.nextElement(), null);
// ArrayIndexOutOfBoundsException, if setting font here...
// list.setFont(i, f);
}

you might want to do something like this :

Enumeration e = v.elements();
while( e.hasNextElement()
{
list.append((String)e.nextElement(), null);
// ArrayIndexOutOfBoundsException, if setting font here...
// list.setFont(i, f);
}

[lianergoist]

Maybe you might want to do some System.out.println within your :

for (i=1 ; i<list.size() ; i++ ) {
// It's okay here...
list.setFont(i, f);
}

just to check where it al goes wrong ?

Well, it makes sense why I can't apply font size here:

 
        int i = 0;
        for (Enumeration e = v.elements(); e.hasMoreElements(); i++ ) {
            list.append((String)e.nextElement(), null);
            // ArrayIndexOutOfBoundsException, if setting font here...
            // list.setFont(i, f);
        }

but I can here:

 
        for (i=1 ; i<list.size() ; i++ ) {
            // It's okay here...
            list.setFont(i, f);
        }

when we look at what makes the exception, when running the reload command. The only thing that happens in the reload scope, is we append an element to the list. That's not normally a problem, and if we comment out the list.setFont code, there is no problem appending another element. But if we use setFont first, and then append an element, we get the exception. So, in this code:

 
        int i = 0;
        for (Enumeration e = v.elements(); e.hasMoreElements(); i++ ) {
            list.append((String)e.nextElement(), null);
            // ArrayIndexOutOfBoundsException, if setting font here...
            list.setFont(i, f);
        }

the first element is appended successfully, and setFont will also apply font successfully, but next element will create an exception. I don't think it should, and I don't understand why, but it does. It is exactly what happens in the reload command scope:

 public void commandAction (Command c, Displayable d) {
        if (c == reloadcmd) {


//            list.deleteAll();
//            int i = 0;
//            for (Enumeration e = v.elements(); e.hasMoreElements(); i++ ) {
//                list.append((String)e.nextElement(), null);
//            }

            list.append("test", null);
        
//            for (i=0 ; i<list.size() ; i++ ) {
//                if (!list.getFont(i).equals(f)){
//                    list.setFont(i, f);
//                }
//            }

            display.setCurrent(list);
        
        }

Also shouldn't the variable i be initialised with 0 ?

Well, yes. It was only to show the diffedrence in font size.

Personally looking at your error I think something is going wrong here :

for (Enumeration e = v.elements(); e.hasMoreElements(); i++ ) {
list.append((String)e.nextElement(), null);
// ArrayIndexOutOfBoundsException, if setting font here...
// list.setFont(i, f);
}

you might want to do something like this :

Enumeration e = v.elements();
while( e.hasNextElement()
{
list.append((String)e.nextElement(), null);
// ArrayIndexOutOfBoundsException, if setting font here...
// list.setFont(i, f);
}

No, it's actually working well. It may be a little harder to read, but it does the same.

[Tiger79]

hhmm, sorry then I don't have a clue :P
It does sound stupid though that you have to set the Font for every specific item within a list (or choicegroup). It would sound more logical to me (especially to keep a list looks uniform) to do that once for the whole list, as it being a setting/parameter of the whole list which will be passed down to its children (thus the entries within the list)... Anyhow thats some personal mumbling

[lianergoist]

It does sound stupid though that you have to set the Font for every specific item within a list (or choicegroup).

Yes, but doing it on individual elements let you 'highligt' the selected element. Well, that's maybe not a good reason, but... ;-)

BTW - I have been looking a bit deeper into it. I'm not familiar with java (OO) design and terminology, so maybe I use some wrong terms here, but... the choicegroup documentation say:

"Each element of a Choice is composed of a text string part, an Image part, and a font attribute that are all treated as a unit. "

... "as a unit". But when I ran some some test code in the debugger, font was not part of each element, but a part of the choicegroup. 'fontEls' is an unallocated array of Font objects in choicegroup until you use setFont() first time. Then it is created with a size equal the current number of elements in the list, and a font object is added to one of the array elements. So far, so good. What I would expect now was, when I used append(), the fontEls array were reallocated to hold the new number of elements. But we newer get so far, because using append() after fontEls is allocated, throws an ArrayIndexOutOfBoundsException.

I don't see other solutions than deleting the list/choicegroup and create it again with the new size. And it's not a big problem to do that, because it it all happens so extremely fast, so no one will ever notice this ugly hack... ;-)