UICollectionView con un encabezado pegajoso

La solución más simple para iOS 9 + ya que no necesita escribir subclase de UICollectionViewFlowLayout.

En viewDidLoad de ViewController con collectionView use el siguiente código:

let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout // casting is required because UICollectionViewLayout doesn't offer header pin. Its feature of UICollectionViewFlowLayout
layout?.sectionHeadersPinToVisibleBounds = true

Esta es realmente una buena solución y funciona perfectamente. Sin embargo, dado que tenemos que devolver YES from shouldINvalidateLayoutForBoundsChange, esto básicamente llama a Prepararlayout cada vez que se desplaza la vista. Ahora, SI su Preparlayout tiene la responsabilidad de crear los atributos de diseño, lo cual es bastante común, esto afectará enormemente el rendimiento del desplazamiento.

Una solución, que funcionó para mí, es no crear los atributos de diseño en Preparlayout, sino hacerlo en un método separado que llama explícitamente antes de llamar invalidateLayout. UICollectionView llama a Preparlayout cuando siente que necesita saber sobre el diseño y, por lo tanto, esta solución también se encargará de esos casos.

Este código funciona para mí

    -(NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
        NSMutableArray *answer = [[super layoutAttributesForElementsInRect:rect] mutableCopy];
        UICollectionView * const cv = self.collectionView;
        //CLS_LOG(@"Number of sections = %d", [cv numberOfSections]);
        CGPoint const contentOffset = cv.contentOffset;

    //CLS_LOG(@"Adding missing sections");
    NSMutableIndexSet *missingSections = [NSMutableIndexSet indexSet];
    for (UICollectionViewLayoutAttributes *layoutAttributes in answer) {
        if (layoutAttributes.representedElementCategory == UICollectionElementCategoryCell) {
            [missingSections addIndex:layoutAttributes.indexPath.section];
        }
    }
    for (UICollectionViewLayoutAttributes *layoutAttributes in answer) {
        if ([layoutAttributes.representedElementKind isEqualToString:UICollectionElementKindSectionHeader]) {
            [missingSections removeIndex:layoutAttributes.indexPath.section];
        }
    }

    [missingSections enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {

        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:idx];

        UICollectionViewLayoutAttributes *layoutAttributes = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader atIndexPath:indexPath];

        [answer addObject:layoutAttributes];

    }];

    NSInteger numberOfSections = [cv numberOfSections];

    //CLS_LOG(@"For loop");
    for (UICollectionViewLayoutAttributes *layoutAttributes in answer) {

        if ([layoutAttributes.representedElementKind isEqualToString:UICollectionElementKindSectionHeader]) {

            NSInteger section = layoutAttributes.indexPath.section;
            //CLS_LOG(@"Customizing layout attribute for header in section %d with number of items = %d", section, [cv numberOfItemsInSection:section]);

            if (section < numberOfSections) {
                NSInteger numberOfItemsInSection = [cv numberOfItemsInSection:section];

                NSIndexPath *firstObjectIndexPath = [NSIndexPath indexPathForItem:0 inSection:section];
                NSIndexPath *lastObjectIndexPath = [NSIndexPath indexPathForItem:MAX(0, (numberOfItemsInSection - 1)) inSection:section];

                BOOL cellsExist;
                UICollectionViewLayoutAttributes *firstObjectAttrs;
                UICollectionViewLayoutAttributes *lastObjectAttrs;

                if (numberOfItemsInSection > 0) { // use cell data if items exist
                    cellsExist = YES;
                    firstObjectAttrs = [self layoutAttributesForItemAtIndexPath:firstObjectIndexPath];
                    lastObjectAttrs = [self layoutAttributesForItemAtIndexPath:lastObjectIndexPath];
                } else { // else use the header and footer
                    cellsExist = NO;
                    firstObjectAttrs = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                                                                            atIndexPath:firstObjectIndexPath];
                    lastObjectAttrs = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionFooter
                                                                           atIndexPath:lastObjectIndexPath];

                }

                CGFloat topHeaderHeight = (cellsExist) ? CGRectGetHeight(layoutAttributes.frame) : 0;
                CGFloat bottomHeaderHeight = CGRectGetHeight(layoutAttributes.frame);
                CGRect frameWithEdgeInsets = UIEdgeInsetsInsetRect(layoutAttributes.frame,
                                                                   cv.contentInset);

                CGPoint origin = frameWithEdgeInsets.origin;

                origin.y = MIN(
                               MAX(
                                   contentOffset.y + cv.contentInset.top,
                                   (CGRectGetMinY(firstObjectAttrs.frame) - topHeaderHeight)
                                   ),
                               (CGRectGetMaxY(lastObjectAttrs.frame) - bottomHeaderHeight)
                               );

                layoutAttributes.zIndex = 1024;
                layoutAttributes.frame = (CGRect){
                    .origin = origin,
                    .size = layoutAttributes.frame.size
                };
            }
        }

    }

    return answer;

}

- (BOOL) shouldInvalidateLayoutForBoundsChange:(CGRect)newBound {
    return YES;
}

Prueba esto chicos...

Solo necesita crear un nuevo UICollectionViewFlowLayout con este código:

class StickyHeaderLayout: UICollectionViewFlowLayout {

    override init() {
        super.init()
        self.sectionFootersPinToVisibleBounds = true
        self.sectionHeadersPinToVisibleBounds = true
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.sectionFootersPinToVisibleBounds = true
        self.sectionHeadersPinToVisibleBounds = true
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard let attributes = super.layoutAttributesForElements(in: rect) else { return nil }

        for attribute in attributes {
            adjustAttributesIfNeeded(attribute)
        }
        return attributes
    }

    override func layoutAttributesForSupplementaryView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        guard let attributes = super.layoutAttributesForSupplementaryView(ofKind: elementKind, at: indexPath) else { return nil }
        adjustAttributesIfNeeded(attributes)
        return attributes
    }

    func adjustAttributesIfNeeded(_ attributes: UICollectionViewLayoutAttributes) {
        switch attributes.representedElementKind {
        case UICollectionElementKindSectionHeader?:
            adjustHeaderAttributesIfNeeded(attributes)
        case UICollectionElementKindSectionFooter?:
            adjustFooterAttributesIfNeeded(attributes)
        default:
            break
        }
    }

    private func adjustHeaderAttributesIfNeeded(_ attributes: UICollectionViewLayoutAttributes) {
        guard let collectionView = collectionView else { return }
        guard attributes.indexPath.section == 0 else { return }

        if collectionView.contentOffset.y < 0 {
            attributes.frame.origin.y = collectionView.contentOffset.y
        }
    }

    private func adjustFooterAttributesIfNeeded(_ attributes: UICollectionViewLayoutAttributes) {
        guard let collectionView = collectionView else { return }
        guard attributes.indexPath.section == collectionView.numberOfSections - 1 else { return }

        if collectionView.contentOffset.y + collectionView.bounds.size.height > collectionView.contentSize.height {
            attributes.frame.origin.y = collectionView.contentOffset.y + collectionView.bounds.size.height - attributes.frame.size.height
        }
    }

}

Nada de lo anterior funcionó para mí. Estaba buscando un diseño limpio que, cuidando mis inserciones, me diera una foto.colección de desplazamiento de estilo de aplicación.

Adapté la solución prosed aquí para cuidar la configuración de EdgeInsets. Para mayor claridad adjunto la solución completa aquí. Sin embargo, puede obtener la solución completa de la siguiente síntesis: #3e1955a4492a897e677f.

@implementation SpringboardLayout

- (id)init
{
    if (self = [super init])
    {
        self.headerReferenceSize = CGSizeMake(0, 50);
        self.footerReferenceSize = CGSizeMake(0, 0);
        self.sectionInset = UIEdgeInsetsMake(10, 10, 80, 10);
        self.scrollDirection = UICollectionViewScrollDirectionVertical;
        self.minimumInteritemSpacing = 10;
        self.minimumLineSpacing = 10;
        if(IS_IPHONE_6 || IS_IPHONE_6PLUS) {
            self.itemSize = CGSizeMake(100, 128);
        } else {
            self.itemSize = CGSizeMake(80, 108);
        }
    }
    return self;
}

- (BOOL) shouldInvalidateLayoutForBoundsChange:(CGRect)newBound {
    return YES;
}

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {

    NSMutableArray *answer = [[super layoutAttributesForElementsInRect:rect] mutableCopy];
    UICollectionView * const cv = self.collectionView;
    CGPoint const contentOffset = cv.contentOffset;

    NSMutableIndexSet *missingSections = [NSMutableIndexSet indexSet];

    for (UICollectionViewLayoutAttributes *layoutAttributes in answer) {
        if (layoutAttributes.representedElementCategory == UICollectionElementCategoryCell) {
            [missingSections addIndex:layoutAttributes.indexPath.section];
        } else if ([layoutAttributes.representedElementKind isEqualToString:UICollectionElementKindSectionHeader]) {
            [missingSections removeIndex:layoutAttributes.indexPath.section];
        }
    }

    [missingSections enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {

        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:idx];

        UICollectionViewLayoutAttributes *layoutAttributes = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader atIndexPath:indexPath];

        [answer addObject:layoutAttributes];

    }];

    for (UICollectionViewLayoutAttributes *layoutAttributes in answer) {

        if ([layoutAttributes.representedElementKind isEqualToString:UICollectionElementKindSectionHeader]) {

            NSInteger section = layoutAttributes.indexPath.section;
            NSInteger numberOfItemsInSection = [cv numberOfItemsInSection:section];

            NSIndexPath *firstObjectIndexPath = [NSIndexPath indexPathForItem:0 inSection:section];
            NSIndexPath *lastObjectIndexPath = [NSIndexPath indexPathForItem:MAX(0, (numberOfItemsInSection - 1)) inSection:section];

            BOOL cellsExist;
            UICollectionViewLayoutAttributes *firstObjectAttrs;
            UICollectionViewLayoutAttributes *lastObjectAttrs;

            if (numberOfItemsInSection > 0) { // use cell data if items exist
                cellsExist = YES;
                firstObjectAttrs = [self layoutAttributesForItemAtIndexPath:firstObjectIndexPath];
                lastObjectAttrs = [self layoutAttributesForItemAtIndexPath:lastObjectIndexPath];
            } else { // else use the header and footer
                cellsExist = NO;
                firstObjectAttrs = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                                                                        atIndexPath:firstObjectIndexPath];
                lastObjectAttrs = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionFooter
                                                                       atIndexPath:lastObjectIndexPath];

            }

            CGFloat topHeaderHeight = (cellsExist) ? CGRectGetHeight(layoutAttributes.frame) : 0;
            CGFloat bottomHeaderHeight = CGRectGetHeight(layoutAttributes.frame);
            CGRect frameWithEdgeInsets = UIEdgeInsetsInsetRect(layoutAttributes.frame,
                                                               cv.contentInset);

            CGPoint origin = frameWithEdgeInsets.origin;


            origin.y = MIN(MAX(contentOffset.y + cv.contentInset.top,
                               (CGRectGetMinY(firstObjectAttrs.frame) - topHeaderHeight - self.sectionInset.top))
                           ,(CGRectGetMaxY(lastObjectAttrs.frame) - bottomHeaderHeight + self.sectionInset.bottom));
            layoutAttributes.zIndex = 1024;
            layoutAttributes.frame = (CGRect){
                .origin = origin,
                .size = layoutAttributes.frame.size
            };
        }
    }
    return answer;
}

@end