Problem in changing List control's font..!!

Question

Hi.. I'm having this problem where if I take a listbox & add 15 items to it & change the font of each item in a loop
using the function below, it works perfect..
//sets font for every item in List used in the application
     private void SetListBoxItemsFont(List lstBx)
          Font FONT_APPLICATION = Font.getFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_SMALL);
          for(int i=0;i<lstBx.size();i++)
               lstBx.setFont(i, FONT_APPLICATION);
     }     but now if I clear the list control & add 5 items(less than the earlier one)
and call out the same function to change the font.. it throws an error..
java.lang.ArrayIndexOutOfBoundsException
     at javax.microedition.lcdui.ChoiceGroup.insertImpl(+317)
     at javax.microedition.lcdui.ChoiceGroup.append(+25)
     at javax.microedition.lcdui.List.append(+9)
     at TimingsDialog.SetTimings(+128)
     at SelectRoutesDialog.commandAction(+189)
     at javax.microedition.lcdui.List.callKeyPressed(+80)
     at javax.microedition.lcdui.Display$DisplayAccessor.keyEvent(+198)
     at javax.microedition.lcdui.Display$DisplayManagerImpl.keyEvent(+11)
     at com.sun.midp.lcdui.DefaultEventHandler.keyEvent(+121)
     at com.sun.midp.lcdui.AutomatedEventHandler.keyEvent(+210)
     at com.sun.midp.lcdui.DefaultEventHandler$QueuedEventHandler.run(+178)
what do you think is the problem?? please help...

Answer 1

Hi Dayson, this is how far I could get --
The top of the stack trace in NetBeans:
java.lang.ArrayIndexOutOfBoundsException
        at javax.microedition.lcdui.ChoiceGroup.insertImpl(ChoiceGroup.java:1402)
        at javax.microedition.lcdui.ChoiceGroup.append(ChoiceGroup.java:388)
        at javax.microedition.lcdui.List.append(List.java:423)List.append    public int append(String stringPart, Image imagePart) {
        return cg.append(stringPart, imagePart);
cg is an instance field, class of cg is ChoiceGroup.
ChoiceGroup.append    public int append(String stringPart, Image imagePart) {
        int returnVal = -1;
        synchronized (Display.LCDUILock) {
            checkNull(stringPart, imagePart);
            returnVal = insertImpl(numOfEls, stringPart, imagePart);
        return returnVal;
    }ChoiceGroup.insertImpl    private int insertImpl(int elementNum, String stringPart,
                           Image imagePart) {
        if (numOfEls == stringEls.length) {
            String[] newStrings = new String[stringEls.length + 4];
            System.arraycopy(stringEls, 0, newStrings, 0, elementNum);
            System.arraycopy(stringEls, elementNum, newStrings,
                             elementNum + 1, numOfEls - elementNum);
            stringEls = newStrings;
            if (imageEls != null) {
                Image[] newImages = new Image[imageEls.length + 4];
                Image[] newMutableImages = new Image[imageEls.length + 4];
                System.arraycopy(imageEls, 0, newImages, 0, elementNum);
                System.arraycopy(imageEls, elementNum, newImages,
                                 elementNum + 1, numOfEls - elementNum);
                System.arraycopy(mutableImageEls, 0, newMutableImages,
                                 0, elementNum);
                System.arraycopy(mutableImageEls, elementNum, newMutableImages,
                                 elementNum + 1, numOfEls - elementNum);
                imageEls = newImages;
                mutableImageEls = newMutableImages;
            if (fontEls != null) {
                Font[] newFonts = new Font[fontEls.length + 4];
                System.arraycopy(fontEls, 0, newFonts, 0, elementNum);
                System.arraycopy(fontEls, elementNum, newFonts,
                                 elementNum + 1, numOfEls - elementNum);
        } else {
            System.arraycopy(stringEls, elementNum, stringEls, elementNum + 1,
                             numOfEls - elementNum);
            if (imageEls != null) {
                System.arraycopy(imageEls, elementNum, imageEls,
                                 elementNum + 1, numOfEls - elementNum);
                System.arraycopy(mutableImageEls, elementNum, mutableImageEls, // line 1402
                                 elementNum + 1, numOfEls - elementNum);
            if (fontEls != null) {
                System.arraycopy(fontEls, elementNum, fontEls,
                                 elementNum + 1, numOfEls - elementNum);
        if (choiceType == Choice.MULTIPLE) {
            if (selEls.length == numOfEls) {
                boolean newSelEls[] = new boolean[numOfEls + 4];
                System.arraycopy(selEls, 0, newSelEls, 0, elementNum);
                System.arraycopy(selEls, elementNum, newSelEls, elementNum + 1,
                                 numOfEls - elementNum);
                selEls = newSelEls;
            } else {
                System.arraycopy(selEls, elementNum, selEls, elementNum + 1,
                                 numOfEls - elementNum);
            selEls[elementNum] = false;
        stringEls[elementNum] = null;
        if (imageEls != null) {
            imageEls[elementNum] = null;
            mutableImageEls[elementNum] = null;
        if (fontEls != null) {
            fontEls[elementNum] = null;
        numOfEls++;
        if (choiceType != Choice.MULTIPLE &&
                (elementNum < selectedIndex || selectedIndex == -1)) {
            selectedIndex++;
            hilightedIndex = selectedIndex;
        } else if (elementNum < hilightedIndex || hilightedIndex == -1) {
            hilightedIndex++;
        setImpl(elementNum, stringPart, imagePart);
        return elementNum;
    }I've marked line 1402, but that line relates to the images array. However, 5 lines down, line 1407 is concerned with the fonts array, so I'm assuming the code I have is slightly different from the one compiled to the ChoiceGroup.class used by NetBeans.
This is the declaration, with comments, for fontEls, the fonts array:    /**
     * The array containing the Font of each element (null if no setFont()
     * method was ever called). If fontEls is non-null, only the elements
     * which were set by setFont() are non-null.
    private Font[] fontEls;So this becomes apparent: fontEls is non-null after setFont() has been called. Now review the code block around line 1407:            if (fontEls != null) {
                System.arraycopy(fontEls, elementNum, fontEls,
                                 elementNum + 1, numOfEls - elementNum);
            }BUT... nowhere in the code do I find a new array being assigned to fontEls, EXCEPT in the setFont method, and that too only once... here's List.setFont    public void setFont(int elementNum, Font font) {
         cg.setFont(elementNum, font);
    } and ChoiceGroup.setFont    public void setFont(int elementNum, Font font) {
        synchronized (Display.LCDUILock) {
            checkIndex(elementNum);
            if (fontEls == null) {
                fontEls = new Font[numOfEls];
            fontEls[elementNum] = font;
    }With this knowledge, I reduced your code to the smallest possible that should demonstrate the bug -- and I did get the NullPointerException thrown by ChoiceGroup.insertImpl. This is the code I tested:package dayson;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.List;
public class TestList extends List {
    final Font FONT_APPLICATION = Font.getFont (Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_SMALL);
    public TestList () {
        super ("", List.IMPLICIT);
        append ("", null);
        setFont (0, FONT_APPLICATION);
        append ("", null);
}I think this makes enough sense to submit a bug report to Sun. Would you like to do the honours? Do post the bug ID here, I believe there's a system of voting for bugs -- the bugs with the most votes get fixed soonest.
db
To other readers of this: sorry for the length of this post, but the topic merited it.