Question

I have a button that, when selected, I want to use it to display an artwork image, but when not selected, I want to display a background image. The button is called the albumArtworkView button and is essentially a toggle between display modes. While in the selected state, new artwork is displayed periodically. In order for the displayed image to be a sharp image, I’ve found that the artwork must be resized to the bounds of the albumArtworkView button as shown in the lines of the following routine:

-(void) handleChangesToArtwork {
    ...
    MPMediaItemArtwork *artwork = [currentItem valueForProperty: MPMediaItemPropertyArtwork];
    if (artwork) {
        artworkImage = [artwork imageWithSize: CGSizeMake (10, 10)]; // size for nav button
    }

    ...

    if (albumArtworkShowing) {
        artworkImage = [artwork imageWithSize: albumArtworkView.bounds.size]; // resize artwork for albumArtworkView button
        [albumArtworkView setImage:artworkImage forState: UIControlStateNormal];
    }
    ...
}

Now artworkImage and albumArtworkView are defined as follows:

@interface RootViewController : UIViewController <...> {
UIImage           *artworkImage;
IBOutlet UIButton *albumArtworkView;
}

-(IBAction) showAlbumArtwork:(id)sender;

@property (nonatomic, retain) UIImage           *artworkImage;
@property (nonatomic, retain) IBOutlet UIButton *albumArtworkView;

Notice the definition of the showAlbumArtwork method to handle the button selection action. This method is implemented as follows:

-(IBAction) showAlbumArtwork:(id)sender {
    if (albumArtworkShowing) {
        [self setAlbumArtworkShowing:FALSE];
        [albumArtworkView setImage:[UIImage imageNamed: @"backgroundImage.png"] forState: UIControlStateNormal];
    }
    else {
        [self setAlbumArtworkShowing:TRUE];
        if (artworkImage) {
            [albumArtworkView setImage:artworkImage forState: UIControlStateNormal];    // Now change the look of the albumArtworkView (speaker button) to the newly sized artworkImage
        }
        else {
            [albumArtworkView setImage:[UIImage imageNamed: @"no_artwork.png"] forState: UIControlStateNormal];
        }

    }

}

So, if I run the above code, there are no crashes. However, the first display of the artwork when I press the button is fuzzy (because as you can see from the logic above, it is using a cgsize of 10,10). But now that the albumArtworkView button has been selected and the albumArtworkShowing flag is now TRUE, every subsequent execution of handleChangesToArtwork resizes the artwork to the bounds of the albumArtworkView button and the images are no longer fuzzy.

If I modify the handleChangesToArtwork routine above to include an else when the albumArtworkShowing flag is FALSE as shown below:

-(void) handleChangesToArtwork {
    ...
    if (albumArtworkShowing) {
        ...
    }
    else {
        artworkImage = [artwork imageWithSize: albumArtworkView.bounds.size];
    }
}

then that is when I get a EXC_BAD_ACCESS. This error occurs in the showAlbumArtwork method when the button is selected. Specifically it occurs on the line with the setImage.

I suspect that I must have some memory management issue, but I am not sure where.

Can anyone see the errors of my ways?

Answer 1

Change

artworkImage = [artwork imageWithSize: albumArtworkView.bounds.size];

to

self.artworkImage = [artwork imageWithSize: albumArtworkView.bounds.size];

This will make sure the artworkImage property’s setter is used, which retains the instance. In your current code you assign an autoreleased UIImage to artworkImage without retaining it, causing the EXC_BAD_ACCESS.