MPMediaItemPropertyArtwork causes crash (weird issue)

问题:

allocations before running 'extra loop'

The code:

// loading items to the array, there are no memory warnings after this is completed. The first allocations screenshot is after this code and before extra loop code. NSMutableArray *albumCovers = [[NSMutableArray alloc] init]; for (MPMediaQuery *query in queries) {     NSArray *allCollections = [query collections];     for (MPMediaItemCollection *collection in allCollections) {         MPMediaItemArtwork *value = [collection.representativeItem valueForProperty:MPMediaItemPropertyArtwork];                 UIImage *image = [value imageWithSize:CGSizeMake(100, 100)];                 if (image) {                     [albumCovers addObject:image];                 }             }         }     }     _mediaCollections = [NSArray arrayWithArray:artworkedCollections];     _albumCovers = [NSArray arrayWithArray:albumCovers]; } 

And somewhere else:

// !!!!! extra loop - from here the memory starts to grow and never release for (i=0; i< 800; i++) {     UIImage * coverImage = [_albumCovers objectAtIndex:indexPath.row];     [veryTemp setImage:coverImage]; // exactly this line adds to the memory. with this line commented, there is no problem. } 

allocations after running 'extra loop'

and to clarify, call stack with only-obj-c on and system libraries off (if i turn them on, the highest % is 0.9% per heaviest method)

I've made some research, and found at stackoverflow, that these VM:ImageIO_PNG_Data are usually comming from [UIImage imageNamed:], however as you can see i don't use this method, i'm just getting the reference from MPMediaItemCollection.

回答1:

The problem was that UIImage usually keeps just a ref(CGImageRef), which is a small one. After displaying items, CGImageRef was 'injected' with information. As a result the table was growing all the time.

The simple but not the most beautiful solution was to use the code:

NSArray = @[obj1, obj2, obj3]; // where obj is custom NSObject and has a UIImage property 

instead of:

NSArray = @[img1, img2, img3]; // where img is of UIImage type 

回答2:

Wrap in @autorelease pool?

Also, why are you setting the image for veryTemp (I assume it's a UIImageView) 800 times in [veryTemp setImage:coverImage]; ?

Finally:

[_albumCovers objectAtIndex:indexPath.row]; 

You're getting the image object at the exact same index (indexPath.row) in your loop. I am not quite sure what you're trying to achieve in your code?

文章来源: MPMediaItemPropertyArtwork causes crash (weird issue)