Unknown why the NullPointerException is thrown

Question

Hey guys,

I'm using a lazy image loader for my ListView with the following code inside getView():

Bitmap cachedImage = asyncImageLoader.loadBitmap(item.getImage(), wallpaperNumber, new ImageCallback()
{
    public void imageLoaded(Bitmap bitmapImage, String wallpaperNumber)
    {
        ImageView imageViewByTag = (ImageView) listView.findViewWithTag(wallpaperNumber);
        imageViewByTag.setImageBitmap(bitmapImage);
    }
});

And the following inside the AsyncImageLoader class:

public Bitmap loadBitmap(final byte[] image, final String wallpaperNumber, final ImageCallback imageCallback) 
{
    if (imageCache.containsKey(wallpaperNumber)) 
    {
        SoftReference<Bitmap> softReference = imageCache.get(wallpaperNumber);
        Bitmap Bitmap = softReference.get();

        if (Bitmap != null) 
        {
            return Bitmap;
        }
    }
    final Handler handler = new Handler() 
    {
        @Override
        public void handleMessage(Message message) 
        {
            try
            {
                if (message.obj != null)
                {                       
                    imageCallback.imageLoaded((Bitmap) message.obj, wallpaperNumber);
                }
                else
                {
                    Bitmap bitmapImage = loadImage(image);
                    imageCache.put(wallpaperNumber, new SoftReference<Bitmap>(bitmapImage));

                    imageCallback.imageLoaded(bitmapImage, wallpaperNumber);
                }
            } 
            catch (Exception e) 
            {
                MiscFunctions.logStackTrace(e);
            }
        }
    };
    new Thread() 
    {
        @Override
        public void run() 
        {
            Bitmap bitmapImage = loadImage(image);
            imageCache.put(wallpaperNumber, new SoftReference<Bitmap>(bitmapImage));
            Message message = handler.obtainMessage(0, bitmapImage);
            handler.sendMessage(message);
        }
    }.start();
    return null;
}

private static Bitmap loadImage(byte[] image) 
{
    Bitmap bitmapImage = BitmapFactory.decodeByteArray(image, 0, image.length);
    bitmapImage = Bitmap.createScaledBitmap(bitmapImage, imageWidth, imageHeight, true);

    return bitmapImage;
}

public interface ImageCallback 
{
    public void imageLoaded(Bitmap imageBitmap, String wallpaperNumber);
}

For an unknown reason to me, after to switched from using the common SQLiteOpenHelper to a custom one which allows me to store my database on the SD card, every 6th or 7th image that is loaded throws a NullPointer at:

imageCallback.imageLoaded((Bitmap) message.obj, wallpaperNumber);

I've checked everything and don't actually know what variable is actually null.

Any help?

Answer 1

I've checked everything and don't actually know what variable is actually null.

Put in a couple of assert statements to check for null (of imageCallback, message, message.obj, wallpaperNumber).