Cell of UICollectionView not always refreshed after a scroll

Question

I have defined in my Storyboard (iPad) a view that contains a UICollectionView, at the bottom of the view there\'s also a UIToolbar. In the UICol

Answer 1

I've had a similar issue. I fixed it by forcing a repaint when setFrame: is called on my custom content. In your case, subclass CPTGraphHostingView and override this method:

-(void)setFrame:(CGRect)frame {
    [super setFrame:frame];
    [self setNeedsDisplay]; // force drawRect:
}

Edit: An easier way to refresh cell views when they are reused is to override applyLayoutAttributes: in iPadCellCollectionViewCell as follows:

-(void)applyLayoutAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes {
    // apply custom attributes...
    [self.hostingView setNeedsDisplay]; // force drawRect:
}

Regarding your workaround: there will be more and more subviews in the content view, which probably isn't a good thing. However, if you'd remove any old subview before adding the new one, that should be OK, too.

Answer 2

This seems to be a bug in UICollectionView when using sectionInsets. The cells don't get invisible, they are misplaced out of bounds sometimes on fast scrolling.

So if you normally would have 3 items per row, you will get a forth item in one row, but no item at the first spot of the next row.

If you set your UICollectionView to not clip to bounds, and move it on top of your UI, you might see this misaligned cell.

My solution was so far to not use sectionInsets, and surround it by using contentInset and some empty space in the section headers.

I also found some other guys at Twitter with the same problem. There's also a bug report about it: 12353513