CODEWITHSUNDEEP
iosobjective-cxcodeios7uicollectionview
DBoyer
DBoyer

Reputation: 3122

UICollectionView header view not dequeueing properly

I am trying to add a header to a collection view. I am using a custom layout that scrolls horizontally, it is used to view a list of avatar images for friends. I can get the header to appear but it does NOT dequeue. As soon as the header view goes off screen, its gone for good. Can anyone figure out why this is?

Thank you!

Collection View data source:

- (UICollectionReusableView *)collectionView:(SWAvatarViewerCollectionView *)collectionView
           viewForSupplementaryElementOfKind:(NSString *)kind
                                 atIndexPath:(NSIndexPath *)indexPath
{

    if (self.showAddAvatarHeaderView && [kind isEqualToString:UICollectionElementKindSectionHeader]) {
        return [collectionView dequeueAddAvatarViewHeaderForIndexPath:indexPath];
    }

    return nil;
}

- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(SWAvatarViewerCollectionViewFlowLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
    if (!self.showAddAvatarHeaderView) {
        return CGSizeZero;
    }

    return CGSizeMake(kSWAvatarViewerAddAvatarHeaderViewWidth, CGRectGetHeight(collectionView.bounds));
}

Avatar collection view:

- (SWAvatarViewerAddAvatarHeaderView *)dequeueAddAvatarViewHeaderForIndexPath:(NSIndexPath *)indexPath {
    SWAvatarViewerAddAvatarHeaderView *headerView = [super dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                                                                             withReuseIdentifier:[SWAvatarViewerAddAvatarHeaderView headerReuseIdentifier]
                                                                                    forIndexPath:indexPath];
    headerView.delegate = self;
    return headerView;
}

Nib file registration:

  [self registerNib:[SWAvatarViewerAddAvatarHeaderView nib]
        forSupplementaryViewOfKind:UICollectionElementKindSectionHeader
        withReuseIdentifier:[SWAvatarViewerAddAvatarHeaderView headerReuseIdentifier]];

Layout:

#pragma mark - Initialization

- (void)configureFlowLayout {
    self.scrollDirection = UICollectionViewScrollDirectionHorizontal;

    // Padding for cells is taken into account in the cell's layout. Remove all
    // padding between cells
    self.sectionInset = UIEdgeInsetsMake(0, 00.0f, 0, 00.0f);
    self.minimumLineSpacing = 0.0f;
    self.minimumInteritemSpacing = CGFLOAT_MAX;

    _cellBottomLabelFont = [UIFont systemFontOfSize:12.0];

    CGSize defaultAvatarSize = CGSizeMake(44.0f, 44.0f);
    _avatarViewSize = defaultAvatarSize;

    _springinessEnabled = YES;
    _springResistanceFactor = 1000;
}

Upvotes: 4

Views: 868

Answers (3)

Bhavesh Lathigara
Bhavesh Lathigara

Reputation: 1415

Just put this method that will solve all the problems

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(-50, 10, 10, 10); //asuming

    //UIEdgeInsetsMake(<#CGFloat top#>, <#CGFloat left#>, <#CGFloat bottom#>, <#CGFloat right#>)
}

Enjoy.

Upvotes: 1

Quxflux
Quxflux

Reputation: 3303

Quick googleing did not unveil the SWAvatarViewerCollectionViewFlowLayout. If you have the sources, you can take a look at the layout code, there should be a method called layoutAttributesForElementsInRect:.

The collection view is dequeuing items as soon as they go offscreen which is determined with the help of the aforementioned method (The layout attributes contain the views center and dimensions). If the method returns always the layout attributes for the header it will not get dequeued.

However if you do not have access to the code (like a static lib) you probably can not do much about it.

Upvotes: 1

matt
matt

Reputation: 535989

You're apparently using a third-party layout I've never heard of. After some discussion with you, my feeling is that my first comment under your question was probably right: the layout itself may be buggy.

In a collection view, the layout attributes of the cells (position, size, transform, alpha, etc.) are the responsibility of the layout. So if something disappears merely because it is scrolled off the screen and then back on, it sounds like the layout itself is not doing its job correctly.

Upvotes: 1

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