I decided to draw my UICollectionViewCell's with drawRect: instead of the custom xib files for performance (as I have shadows and label shadows).
For some reason, since I changed this, my cells not draw with different images each time they are reloaded into the UICollectionView.
When I log the name of the image it is set to load in both the collectionView:cellForItemAtIndexPath and drawRect: it supplies the correct name of the image and the correct index path, yet when I load the app, it muddles them up on scrolling, even though initially, they have loaded correctly.
Here is my code:
viewDidLoad
// Collection cells
//
[self.collectionView registerClass:[CluelessSymbolCell class] forCellWithReuseIdentifier:@"Symbol cell"];
collectionView:cellForItemAtIndexPath
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
CluelessSymbolCell *cell = (CluelessSymbolCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"Symbol cell" forIndexPath:indexPath];
CluelessClue *clue = [self.clues objectAtIndex:indexPath.row];
NSLog(@"(%@) Image: %@", indexPath, [clue.imageNames objectAtIndex:0]);
[cell setClue:clue];
return cell;
}
drawRect: (In cell subclass 'CluelessSymbolCell')
- (void)drawRect:(CGRect)rect
{
NSString *imageName = [NSString stringWithFormat:@"%@-icon-iphone", [self.clue.imageNames objectAtIndex:0]];
// Cell
//
[self.contentView.layer setShadowColor:[UIColor blackColor].CGColor];
[self.contentView.layer setShadowOpacity:0.3f];
[self.contentView.layer setShadowRadius:2.0f];
[self.contentView.layer setShadowOffset:CGSizeZero];
[self.contentView.layer setShadowPath:[UIBezierPath bezierPathWithRect:self.layer.bounds].CGPath];
// Image
//
CALayer *imageLayer = [CALayer layer];
[imageLayer setFrame:rect];
[imageLayer setContents:(id)[[UIImage imageNamed:imageName] CGImage]];
[self.contentView.layer addSublayer:imageLayer];
}
Edit
On logging the sublayers of the cell's content view, I can see that each cell's contentview sublayer has moved to the next cell, what is the reason for this and how do I overcome it?
Log:
2013-02-22 23:41:08.064 Clueless[3462:c07] <NSIndexPath 0x845cb90> 2 indexes [0, 0], (null)
2013-02-22 23:41:08.065 Clueless[3462:c07] <NSIndexPath 0x84435f0> 2 indexes [0, 1], (null)
2013-02-22 23:41:08.066 Clueless[3462:c07] <NSIndexPath 0x8446f50> 2 indexes [0, 2], (null)
2013-02-22 23:41:08.066 Clueless[3462:c07] <NSIndexPath 0x843a060> 2 indexes [0, 3], (null)
2013-02-22 23:41:08.067 Clueless[3462:c07] <NSIndexPath 0x846bc70> 2 indexes [0, 4], (null)
2013-02-22 23:41:08.067 Clueless[3462:c07] <NSIndexPath 0x845cd20> 2 indexes [0, 5], (null)
2013-02-22 23:41:08.068 Clueless[3462:c07] <NSIndexPath 0x845ce60> 2 indexes [0, 6], (null)
2013-02-22 23:41:08.068 Clueless[3462:c07] <NSIndexPath 0x846ce40> 2 indexes [0, 7], (null)
2013-02-22 23:41:08.069 Clueless[3462:c07] <NSIndexPath 0x846c9b0> 2 indexes [0, 8], (null)
2013-02-22 23:41:08.069 Clueless[3462:c07] <NSIndexPath 0x846d880> 2 indexes [0, 9], (null)
2013-02-22 23:41:08.070 Clueless[3462:c07] <NSIndexPath 0x846db20> 2 indexes [0, 10], (null)
2013-02-22 23:41:08.071 Clueless[3462:c07] <NSIndexPath 0x846df30> 2 indexes [0, 11], (null)
2013-02-22 23:41:15.105 Clueless[3462:c07] <NSIndexPath 0x846ec60> 2 indexes [0, 12], (null)
2013-02-22 23:41:15.106 Clueless[3462:c07] <NSIndexPath 0x846efb0> 2 indexes [0, 13], (null)
2013-02-22 23:41:15.107 Clueless[3462:c07] <NSIndexPath 0x846f6d0> 2 indexes [0, 14], (null)
2013-02-22 23:41:15.753 Clueless[3462:c07] <NSIndexPath 0x82492e0> 2 indexes [0, 15], (
"<CALayer: 0x8495840>"
)
2013-02-22 23:41:15.754 Clueless[3462:c07] <NSIndexPath 0x827f750> 2 indexes [0, 16], (
"<CALayer: 0x8491010>"
)
2013-02-22 23:41:15.754 Clueless[3462:c07] <NSIndexPath 0x827f5c0> 2 indexes [0, 17], (
"<CALayer: 0x8493ef0>"
)
2013-02-22 23:41:15.986 Clueless[3462:c07] <NSIndexPath 0x845cb90> 2 indexes [0, 0], (
"<CALayer: 0x8493ef0>"
)
2013-02-22 23:41:15.987 Clueless[3462:c07] <NSIndexPath 0x84435f0> 2 indexes [0, 1], (
"<CALayer: 0x8491010>"
)
2013-02-22 23:41:15.987 Clueless[3462:c07] <NSIndexPath 0x8446f50> 2 indexes [0, 2], (
"<CALayer: 0x8495840>"
)
2013-02-22 23:41:26.161 Clueless[3462:c07] <NSIndexPath 0x827d970> 2 indexes [0, 12], (
"<CALayer: 0x8241e20>"
)
2013-02-22 23:41:26.162 Clueless[3462:c07] <NSIndexPath 0x824e9d0> 2 indexes [0, 13], (
"<CALayer: 0x827bc60>"
)
2013-02-22 23:41:26.163 Clueless[3462:c07] <NSIndexPath 0x827d030> 2 indexes [0, 14], (
"<CALayer: 0x8242fb0>"
)
2013-02-22 23:41:26.776 Clueless[3462:c07] <NSIndexPath 0x82492e0> 2 indexes [0, 15], (
"<CALayer: 0x8491010>"
)
2013-02-22 23:41:26.777 Clueless[3462:c07] <NSIndexPath 0x827f750> 2 indexes [0, 16], (
"<CALayer: 0x8493ef0>"
)
2013-02-22 23:41:26.778 Clueless[3462:c07] <NSIndexPath 0x827f5c0> 2 indexes [0, 17], (
"<CALayer: 0x8495840>"
)
2013-02-22 23:41:26.926 Clueless[3462:c07] <NSIndexPath 0x845cb90> 2 indexes [0, 0], (
"<CALayer: 0x8495840>"
)
2013-02-22 23:41:26.927 Clueless[3462:c07] <NSIndexPath 0x84435f0> 2 indexes [0, 1], (
"<CALayer: 0x8493ef0>"
)
2013-02-22 23:41:26.928 Clueless[3462:c07] <NSIndexPath 0x8446f50> 2 indexes [0, 2], (
"<CALayer: 0x8491010>"
)
I don't know if it's a bug, or some kind of problem my end.
However, it seems that to overcome this you need to force drawRect: inside prepareForReuse
- (void)prepareForReuse
{
[super prepareForReuse];
[self setNeedsDisplay];
}