I'm getting a strange crash in my UICollectionView.
The crashing UICollectionView is embedded in an UICollectionView cell of another UICollectionView.
I can't reproduce the issue, it seems to happen sometimes if the inner UICollectionView get's newly initialized because the outer CollectionView is reloading it's cells.
com.apple.main-thread Crashed
0 libobjc.A.dylib objc_msgSend + 9
1 UIKit -[UICollectionViewData _setLayoutAttributes:atGlobalItemIndex:] + 60
2 UIKit __45-[UICollectionViewData validateLayoutInRect:]_block_invoke_0 + 668
3 UIKit -[UICollectionViewData validateLayoutInRect:] + 1408
4 UIKit -[UICollectionViewData layoutAttributesForElementsInRect:] + 82
5 UIKit -[UICollectionView setCollectionViewLayout:animated:] + 1644
6 MyApp BSCTopnewsCollectionView.m line 52 -[BSCTopnewsCollectionView setupBSCTopnewsCollectionView]
7 MyApp BSCTopnewsCollectionView.m line 27 -[BSCTopnewsCollectionView setWeakDelegatePointer:]
8 Myapp BSCFrontPageViewController.m line 550 -[BSCFrontPageViewController collectionView:cellForItemAtIndexPath:]
9 UIKit -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:] + 252
10 UIKit -[UICollectionView _updateVisibleCellsNow:] + 2672
11 UIKit -[UICollectionView layoutSubviews] + 214
12 UIKit -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 258
13 QuartzCore -[CALayer layoutSublayers] + 214
14 QuartzCore CA::Layer::layout_if_needed(CA::Transaction*) + 460
15 QuartzCore CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 16
16 QuartzCore CA::Context::commit_transaction(CA::Transaction*) + 238
17 QuartzCore CA::Transaction::commit() + 316
18 QuartzCore CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 60
19 CoreFoundation __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 20
25 UIKit UIApplicationMain + 1120
26 MyApp main.m line 16 main
Exception Type:
EXC_BAD_ACCESS
Code:
KERN_INVALID_ADDRESS at 0x158848
What I'm doing in line 52 in setupBSCTopnewsCollectionView is
BSCInfiniteLayout *infiniteLayout = [[BSCInfiniteLayout alloc] init]; (line 52) self.collectionView.collectionViewLayout = infiniteLayout;
Edit: -[BSCFrontPageViewController collectionView:cellForItemAtIndexPath:]
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
if([collectionView isEqual:self.collectionView])
{
if(indexPath.row == 0) // Header Cell
{
BSCTopnewsCollectionView *cell = [collectionView dequeueReusableCellWithReuseIdentifier:BSCHeaderReuseIdentifier forIndexPath:indexPath];
cell.dataSource = self;
cell.weakDelegatePointer = self;
self.topNewsCollectionView = cell;
return cell;
}
else
{
//create normal cells
}
}
else if ([collectionView isEqual:self.topNewsCollectionView.collectionView])
{
BSCTopNewsHeaderCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:BSCTopNewsCellReuseIdentifier forIndexPath:indexPath];
BSCNews *topnews = [self.topNews objectAtIndex:indexPath.row];
[cell setEntity:topnews];
return cell;
}
}
A few clarifications for the method calls there:
- (void)setWeakDelegatePointer:(BSCFrontPageViewController *)weakDelegatePointer
{
_weakDelegatePointer = weakDelegatePointer;
[self setupBSCTopnewsCollectionView];
[self.collectionView reloadData];
}
- (void)setupBSCTopnewsCollectionView
{
self.collectionView.delegate = self.weakDelegatePointer;
self.collectionView.dataSource = self.weakDelegatePointer;
BSCInfiniteLayout *infiniteLayout = [[BSCInfiniteLayout alloc] init];
infiniteLayout.delegate = self;
// Setup Layout
self.collectionView.collectionViewLayout = infiniteLayout;
self.collectionView.showsHorizontalScrollIndicator = NO;
self.collectionView.pagingEnabled = YES;
// Register Cells
[self.collectionView registerNib:[UINib nibWithNibName:@"BSCTopNewsHeaderCell" bundle:nil] forCellWithReuseIdentifier:BSCTopNewsCellReuseIdentifier];
}
Edit3: The crash only seems to occur in special occasions.
If the app was in the background, but still in memory and the user opens it up again. It then checks our API for new data, and if it found something will load them and reload the whole outer collectionView. Thats when the crash occurs.
If the CollectionView is reloaded while the app is running without being in the background in the beginning everything is fine.
To make the setup a bit more clear.
Best Answer
First, drag and drop a UICollectionView to your ViewController in XIB, hook up Delegate, datasource to ViewController(this is only main ViewController)
Don't use 2 different nib cell for 1 CollectionView, because you can only register 1 Nib. Better use DecorationView as HeaderView. Create new class HeaderView : UICollectionReusableView. This UICollectionReusableView is subclass of UIView can reuse inside UICollectionView together with UICollectionViewCell. Now you can register both type:
Next, you drag another UICollectionView to this HeaderView, hook up with IBOutlet inside HeaderView.h. Here, it's better to set Delegate, DataSource to this class for control. Also register what Nib Cell this CollectionView will use. Do it in awakeFromNib because you registerNib before
It's will work well, if you store your datasource outside, just make another property and assign to it, then use for return inside datasource here.
If you want to know when click on Cell inside headerView, Use a customDelegate protocol to send delegate to ViewController when click on HeaderCell.
This is my code, hope you understand and can apply your data here:
https://github.com/lequysang/gitfiles02/blob/master/CollectionViewWithDecorationView.zip