Hi James. I'm struggling with an issue... I'm using your library in a collection view, and I noticed that sometimes the system raises an NSInternalInconsistencyException when scrolling to the bottom. It looks like it's correlated to the amount of cells displayed. I was able to recreate the issue in your sample, by providing only 2 sections, the first one with one item, the second one with 4. (You can find the sample in my fork).
Here's the catch: it only happens when I compile with Xcode 5.1 on an iOS8 device (beta5). If I compile with Xcode6 everything goes smoothly. Given the circumstances it might not even be worth spending too much time fixing this, as it's probably a bug introduced in the latest beta, but if someone with the current iOS8 beta downloads an app from the store with this component, it might crash.
Here's the full stack trace:

2014-08-07 16:03:14.718 CSStickyHeaderFlowLayoutDemo[1538:270805] 
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException',
 reason: 'layout attributes for supplementary item at index path (<NSIndexPath: 0x1a07c410> {length = 2, path = 1 - 0}) 
changed from <CSStickyHeaderFlowLayoutAttributes: 0x16d4a050> index path: (<NSIndexPath: 0x1a08e4c0> {length = 2, path = 1 - 0}); 
element kind: (UICollectionElementKindSectionHeader); 
frame = (0 330; 320 50); 
zIndex = 1024;  
to <CSStickyHeaderFlowLayoutAttributes: 0x1a097e80> index path: (<NSIndexPath: 0x1a07c410> {length = 2, path = 1 - 0}); 
element kind: (UICollectionElementKindSectionHeader); 
frame = (0 278.5; 320 50); 
zIndex = 1024;  without invalidating the layout'

anyway, thanks for your great work. :thumbsup:
Cheers.

"Definition of 'CSStickyHeaderFlowLayout' must be imported from module 'CSStickyHeaderFlowLayout.CSStickyHeaderFlowLayout' before it is required" and "duplicate interface definition" and "Property has a previous declaration" after start use pods with use_frameworks!

If I use insert and performBatchUpdates instead of reloadData I always get the problem where header hidden behind cells

I also got example project https://dl.dropboxusercontent.com/u/2271974/CSStickyHeaderFlowLayout.zip, the part I change is this chunk of code

- (void)add:(id)sender
{

    [self.collectionView performBatchUpdates:^{
        NSArray *new = @[
                         @{@"Twitter":@"http://twitter.com"},
                         @{@"Facebook":@"http://facebook.com"},
                         @{@"Tumblr":@"http://tumblr.com"},
                         @{@"Pinterest":@"http://pinterest.com"},
                         @{@"Instagram":@"http://instagram.com"},
                         @{@"Github":@"http://github.com"},
                         @{@"Twitter":@"http://twitter.com"},
                         @{@"Facebook":@"http://facebook.com"},
                         @{@"Tumblr":@"http://tumblr.com"},
                         @{@"Pinterest":@"http://pinterest.com"},
                         @{@"Instagram":@"http://instagram.com"},
                         @{@"Github":@"http://github.com"},
                         ];
            self.sections = [self.sections arrayByAddingObjectsFromArray:new];

        NSMutableIndexSet *set = [NSMutableIndexSet indexSet];
        NSMutableArray *indexPaths = [NSMutableArray array];

        int startIndex = 0;
    [new enumerateObjectsUsingBlock:^(NSDictionary *item, NSUInteger idx, BOOL *stop) {
        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:startIndex + idx];
        [indexPaths addObject:indexPath];

        [set addIndex:startIndex + idx];

    }];

        [self.collectionView insertSections:set];
        [self.collectionView insertItemsAtIndexPaths:indexPaths];
    } completion:nil];
}

Fatal Exception: NSInternalInconsistencyException layout attributes for supplementary item at index path (<NSIndexPath: 0xc000000000000016> {length = 2, path = 0 - 0}) changed from <CSStickyHeaderFlowLayoutAttributes: 0x14e6a1ad0> index path: (<NSIndexPath: 0xc000000000000016> {length = 2, path = 0 - 0}); element kind: (CSStickyHeaderParallexHeader); frame = (0 0; 0 0); to <CSStickyHeaderFlowLayoutAttributes: 0x151865db0> index path: (<NSIndexPath: 0xc000000000000016> {length = 2, path = 0 - 0}); element kind: (CSStickyHeaderParallexHeader); frame = (0 -1.33333; 414 311.833); without invalidating the layout

Getting a lot of crashes like this with stacktrace:

4 UIKit 0x0000000186c3a87c __45-[UICollectionViewData validateLayoutInRect:]_block_invoke + 1004

5 UIKit 0x0000000186c39f74 -[UICollectionViewData validateLayoutInRect:] + 1492

6 UIKit 0x0000000186c397a0 -[UICollectionView layoutSubviews] + 160

I've noticed that for some of my smaller images, it stops stretching and instead breaks and shows the bg. Is there a way to prevent this or set the threshold when and when not to break the stretching?

I have my UICollectionView backed by a NSFetchedResultsController to insert/update cells.

My cells get inserted as the user scrolls. What seems to happen is the sticky headers scroll down & then return once the bounce deceleration animation is complete.

I think a solution would be to only insert cells once animation deceleration is complete.

For me header was always stretching to more than set size which was not desired behaviour. So I added option to disable this.

Thank you for possible merge.

hi james,

i use CSStickyHeaderFlowLayout for parallax CollectionView, and i add a pulling-to-refresh component on this UICollectionView. and after pulling, there is a strange animation. for clear shown, i set the animation duration to 3 seconds.

stackoverflow

and i setup a sample project, and email to you, thanks a lot @jamztang

The sample you provided using "CSStickyHeaderFlowLayoutAttributes" as parameter type but when i used in swift it came with "UICollectionViewLayoutAttributes" base class

your sample

- (void)applyLayoutAttributes:(CSStickyHeaderFlowLayoutAttributes *)layoutAttributes {

swift

override func applyLayoutAttributes(layoutAttributes: UICollectionViewLayoutAttributes!) {

i created another variable and used this way

let attr = layoutAttributes as! CSStickyHeaderFlowLayoutAttributes

When a project is using Size Classes in interface builder, I've found that the collection view cells are not positioned correctly. Instead, they are shifted to the right and are therefore not completely visible on screen. I've found a workaround that fixes the cell positioning when the collection view will have one cell per row (similar to the UITableView layout). I'm not sure how this would affect other parts of the flow layout, however. Perhaps you could shed some light on this issue. Thanks!

Hi,

I am trying to use the library in a swift project. I am not using storyboards in the application. I took a look at the swift example and implemented it in similar fashion. I also took a look at the obj-c project and make some changes accordingly. But I am not able to achieve the effect where the header would scroll up and the section header of collection view would stick to the top of the view. Below is the link to the video. The example in swift is really basic. Can you please enhance it a bit to show the sticky section header effect.

https://www.dropbox.com/s/26jph7gmswqdher/ScreenCap.mov?dl=0

PS: This is not an issue. Just looking for some help/pointers. I guess people have been successful after a few attempts to get the required effect in swift.

iphonex ios11

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'layout attributes for supplementary item at index path (<NSIndexPath: 0xc000000000000516> {length = 2, path = 5 - 0}) changed from <CSStickyHeaderFlowLayout: 0x7fa0c758e060> indexPath: {5, 0} zIndex: 1024 valid: YES kind: UICollectionElementKindSectionHeader to <CSStickyHeaderFlowLayout: 0x7fa0c7592550> indexPath: {5, 0} zIndex: 1024 valid: YES kind: UICollectionElementKindSectionHeader without invalidating the layout' *** First throw call stack: ( 0 CoreFoundation 0x000000010f3701ab __exceptionPreprocess + 171 1 libobjc.A.dylib 0x000000010ea05f41 objc_exception_throw + 48 2 CoreFoundation 0x000000010f375372 +[NSException raise:format:arguments:] + 98 3 Foundation 0x000000010e4aa089 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193 4 UIKit 0x0000000110ba774a __45-[UICollectionViewData validateLayoutInRect:]_block_invoke + 1558 5 UIKit 0x0000000110ba6baf -[UICollectionViewData validateLayoutInRect:] + 2964 6 UIKit 0x0000000110ba9eff -[UICollectionViewData layoutAttributesForCellsInRect:validateLayout:] + 167 7 UIKit 0x0000000110b32767 -[UICollectionView _computePrefetchCandidatesForVisibleBounds:futureVisibleBounds:prefetchVector:notifyDelegateIfNeeded:] + 127 8 UIKit 0x0000000110b326d8 -[UICollectionView _computePrefetchCandidatesForVelocity:notifyDelegateIfNeeded:] + 225 9 UIKit 0x0000000110b325e3 -[UICollectionView _prefetchItemsForVelocity:maxItemsToPrefetch:invalidateCandidatesOnDirectionChanges:] + 921 10 UIKit 0x0000000110b3ba73 -[UICollectionView layoutSubviews] + 779 11 UIKit 0x00000001101396f5 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1439 12 QuartzCore 0x000000010f8c03ee -[CALayer layoutSublayers] + 153 13 QuartzCore 0x000000010f8c44dd _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 401 14 QuartzCore 0x000000010f84cded _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 365 15 QuartzCore 0x000000010f878704 _ZN2CA11Transaction6commitEv + 500 16 QuartzCore 0x000000010f7c892c _ZN2CA7Display11DisplayLink14dispatch_itemsEyyy + 960 17 QuartzCore 0x000000010f904970 ZL22display_timer_callbackP12__CFMachPortPvlS1 + 248 18 CoreFoundation 0x000000010f2ff9c9 __CFMachPortPerform + 169 19 CoreFoundation 0x000000010f2ff909 CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION + 41 20 CoreFoundation 0x000000010f2ff871 __CFRunLoopDoSource1 + 465 21 CoreFoundation 0x000000010f2f7654 __CFRunLoopRun + 2596 22 CoreFoundation 0x000000010f2f69b9 CFRunLoopRunSpecific + 409 23 GraphicsServices 0x00000001158069c6 GSEventRunModal + 62 24 UIKit 0x00000001100685e8 UIApplicationMain + 159 25 CSStickyHeaderFlowLayoutDemo 0x000000010d5410af main + 111 26 libdyld.dylib 0x00000001167f7d81 start + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException

Anyone knows about this problems?

Test Environment

Swift 4 + XCode 9 + iOS 11

I got an error "prepareLayout"

@implementation CSStickyHeaderFlowLayout

- (void)prepareLayout {
    [super prepareLayout];
}

I am currently using storyboard to create the reusableview and cant make it to work. Appreciate it if you can update the documentation on how to use the class using storyboard. THank you for nice library.

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'layout attributes for supplementary item at index path (<NSIndexPath: 0x174037720> {length = 1, path = 0}) changed from <CSStickyHeaderFlowLayout.CSStickyHeaderFlowLayoutAttributes: 0x10dd20cd0> index path: (<NSIndexPath: 0x1700342a0> {length = 1, path = 0}); element kind: (CSStickyHeaderParallaxHeader); frame = (0 -12; 375 179.768); to <CSStickyHeaderFlowLayout.CSStickyHeaderFlowLayoutAttributes: 0x10df42610> index path: (<NSIndexPath: 0x174037720> {length = 1, path = 0}); element kind: (CSStickyHeaderParallaxHeader); frame = (0 -32; 375 199.768); without invalidating the layout'

This occurred on an iPhone 6s running iOS 10.1.1. My app is written in Swift 3 in Xcode 8.1. CSStickyHeaderFlowLayout v0.2.11 is being used.