Application crashes when setting the horizontal UICollectionView header

Question

I am very new to UICollectionView. And I'm really tired to find out a solution. I am trying to add Header to 3 Horizontally Row. I am using the collection view stream layout.
Here is my code that I am implementing:

- (void)awakeFromNib { self.collectionView.backgroundColor = [UIColor colorWithRed:204.0/255.0 green:204.0/255.0 blue:204.0/255.0 alpha:1.0]; self.collectionView.backgroundColor = [UIColor clearColor]; self.collectionView.backgroundView = [[UIView alloc] initWithFrame:CGRectZero]; UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init]; flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal; flowLayout.itemSize = CGSizeMake(130.0, 170.0); [self.collectionView setCollectionViewLayout:flowLayout]; // Register the colleciton cell [_collectionView registerNib:[UINib nibWithNibName:@"ORGArticleCollectionViewCell" bundle:nil] forCellWithReuseIdentifier:@"ORGArticleCollectionViewCell"]; [self.collectionView registerClass:[_HeaderView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView"]; } #pragma mark - UICollectionViewDataSource methods - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView { return 1; } - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section { if (section == 0) { return [self.collectionData count]; } else if(section == 1) { return [self.collectionData1 count]; } else { return [self.collectionData2 count]; } } - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { ORGArticleCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"ORGArticleCollectionViewCell" forIndexPath:indexPath]; cell.articleTitle.text = [self.collectionData objectAtIndex:[indexPath row]]; NSString *URL = [self.collectionImageData objectAtIndex:indexPath.row]; [cell.articleImage setImageWithURL:[NSURL URLWithString:URL] placeholderImage:[UIImage imageNamed:@"profile-image-placeholder"]]; cell.articleImage.contentMode = UIViewContentModeScaleToFill; cell.articlePrice.text = [self.collectionDataPric objectAtIndex:[indexPath row]]; return cell; } - (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath { NSDictionary *cellData = [self.collectionData objectAtIndex:[indexPath row]]; [[NSNotificationCenter defaultCenter] postNotificationName:@"didSelectItemFromCollectionView" object:cellData]; } - (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section { return 0; } - (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section { return 0; } - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath { UICollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind: UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView" forIndexPath:indexPath]; UILabel *label = (UILabel *)[headerView viewWithTag:10]; if (!label) { label = [[UILabel alloc] initWithFrame:CGRectInset(headerView.bounds, 5, 5)]; label.tag = 10; label.font = [UIFont boldSystemFontOfSize:12]; label.textColor = [UIColor darkGrayColor]; [headerView addSubview:label]; } label.text = [NSString stringWithFormat:@"Section %d", indexPath.section]; return headerView; } - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section { CGSize headerSize = CGSizeMake(320, 44); return headerSize; } 

My App crash in the viewForSupplementaryElementOfKind method when I initialize the title view.
The following is the alarm log:

The application terminated due to the unannounced exception "NSInternalInconsistencyException", reason: "there is no instance of UICollectionViewLayoutAttributes for -layoutAttributesForSupplementaryElementOfKind: UICollectionElementKindSectionHeader on path {length = 2, path = 0 - 0} '

Answer 1

Problem with your code [headerView addSubview:label]; , this is only called when the label is nil. but you must call this statement every time viewForSupplementaryElementOfKind is viewForSupplementaryElementOfKind .

Update the viewForSupplementaryElementOfKind function viewForSupplementaryElementOfKind following code.

 - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath { UICollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind: UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView" forIndexPath:indexPath]; UILabel *label = (UILabel *)[headerView viewWithTag:10]; if (!label) { label = [[UILabel alloc] initWithFrame:CGRectInset(headerView.bounds, 5, 5)]; label.tag = 10; label.font = [UIFont boldSystemFontOfSize:12]; label.textColor = [UIColor darkGrayColor]; } label.text = [NSString stringWithFormat:@"Section %d", indexPath.section]; [headerView addSubview:label]; return headerView; }