Adjust UICollectionViewFlowLayout When UICollectionView Frame Changes - objective-c

Question

I have a UICollectionView that I created programmatically, along with its UICollectionViewFlowLayout. The code for this looks like:
- (UICollectionView *)createCollectionToDisplayContent:(NSArray *)array ViewWithCellIdentifier:(NSString *)cellIdentifier ofWidth:(CGFloat)width withHeight:(CGFloat)height forEmailView:(EmailView *)emailView
{
CGFloat minInterItemSpacing;
if (!self.orientationIsLandscape) minInterItemSpacing = 9.0f;
else minInterItemSpacing = 20.0f;
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];
layout.itemSize = CGSizeMake(220.0f, 45.0f);
layout.sectionInset = UIEdgeInsetsMake(5.0f, 0.0f, 5.0f, 0.0f);
layout.minimumLineSpacing = 10.0f;
layout.minimumInteritemSpacing = minInterItemSpacing;
//get pointer to layout so I can change it later
emailView.personLabelsLayout = layout;
UICollectionView *collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(40, 4, width, height) collectionViewLayout:layout];
collectionView.dataSource = emailView;
collectionView.delegate = emailView;
collectionView.scrollEnabled = NO;
collectionView.userInteractionEnabled = YES;
collectionView.backgroundColor = [UIColor clearColor];
[collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:cellIdentifier];
collectionView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleBottomMargin);
[collectionView reloadData];
return collectionView;
}
This code works fine to initially display the collection view. My issue is in trying to change the flow layout when the device is rotated. I handle the change in the collection view frame using struts and springs (see above), and in the willAnimateRotationToInterfaceOrientation method, I adjust the minimumInterItemSpacing property of the flow layout, and finally call reload data on the collection view. Here is the code for that:
- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
CGFloat minInterItemSpacing;
if (toInterfaceOrientation == UIInterfaceOrientationLandscapeLeft || toInterfaceOrientation == UIInterfaceOrientationLandscapeRight) {
minInterItemSpacing = 20.0f;
} else {
minInterItemSpacing = 9.0f;
}
self.visibleEmailView = //...more code
self.visibleEmailView.personLabelsLayout.minimumInteritemSpacing = minInterItemSpacing;
[self.visibleEmailView.personLabelsCollectionView reloadData];
//other stuff...
}
Ultimately, the flow layout should adjust dramatically when the view is rotated: in terms of the minimumInterItemSpacing but also in terms of the number of columns it displays. However, the layout is not adjusting as I would expect. I am having trouble figuring out what exactly is even happening. It looks like the minimumInterItemSpacing is not being reset on rotation, and it looks like for each cell, the same cell is being drawn over itself multiple times. Also, I'm getting crashes that say:
"the collection view's data source did not return a valid cell from -collectionView:cellForItemAtIndexPath: for index path <NSIndexPath 0x9be47e0> 2 indexes [0, 6]"
In trying to begin to narrow down what is going on here, I am wondering if anyone can tell me if my approach is correct, and/or if there is an obvious error in my code that might be causing some or all of this funky behavior.

Answer 1

Are you implementing anything like this?
- (BOOL) shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
return YES;
]