ios 9以後UICollectionViewFlowLayout中新增了sectionHeadersPinToVisibleBounds
@property (nonatomic) BOOL sectionHeadersPinToVisibleBounds API_AVAILABLE(ios(9.0));
設置
layou.sectionHeadersPinToVisibleBounds = YES;
[layout setScrollDirection:UICollectionViewScrollDirectionVertical];//上下滑動的
就可以讓UICollectionView的所有header懸停，
如果想要某個Section的Header懸停的話，就要 繼承UICollectionViewFlowLayout，重寫方法
//在layoutAttributesForSupplementaryViewOfKind方法中添加限制條件就可以設置某個Section懸停
- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect
{
NSMutableArray *superArray = [[super layoutAttributesForElementsInRect:rect] mutableCopy];
NSMutableIndexSet *missingSections = [NSMutableIndexSet indexSet];
for (NSUInteger idx=0; idx<[superArray count]; idx++) {
UICollectionViewLayoutAttributes *layoutAttributes = superArray[idx];
if (layoutAttributes.representedElementCategory == UICollectionElementCategoryCell) {
[missingSections addIndex:layoutAttributes.indexPath.section]; // remember that we need to layout header for this section
}
if ([layoutAttributes.representedElementKind isEqualToString:UICollectionElementKindSectionHeader]) {
[superArray removeObjectAtIndex:idx]; // remove layout of header done by our super, we will do it right later
idx--;
}
}
// layout all headers needed for the rect using self code
[missingSections enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:idx];
UICollectionViewLayoutAttributes *layoutAttributes = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader atIndexPath:indexPath];
if (layoutAttributes) {
[superArray addObject:layoutAttributes];
}
}];
for (UICollectionViewLayoutAttributes *attr in self.decorationViewAttrs) {
if (CGRectIntersectsRect(rect, attr.frame)) {
[superArray addObject:attr];
}
}
return [superArray copy];
}
- (UICollectionViewLayoutAttributes *)layoutAttributesForSupplementaryViewOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
UICollectionViewLayoutAttributes *attributes = [super layoutAttributesForSupplementaryViewOfKind:kind atIndexPath:indexPath];
//添加 indexPath.section == 3條件是爲了讓第三個Section懸停，其他的正常，如果不設置，就是所有的都懸停
if ([kind isEqualToString:UICollectionElementKindSectionHeader] && indexPath.section == 3) {
UICollectionView * const cv = self.collectionView;
CGPoint const contentOffset = cv.contentOffset;
CGPoint nextHeaderOrigin = CGPointMake(INFINITY, INFINITY);
if (indexPath.section+1 < [cv numberOfSections]) {
UICollectionViewLayoutAttributes *nextHeaderAttributes = [super layoutAttributesForSupplementaryViewOfKind:kind atIndexPath:[NSIndexPath indexPathForItem:0 inSection:indexPath.section+1]];
nextHeaderOrigin = nextHeaderAttributes.frame.origin;
}
CGRect frame = attributes.frame;
if (self.scrollDirection == UICollectionViewScrollDirectionVertical) {
frame.origin.y = MIN(MAX(contentOffset.y, frame.origin.y), nextHeaderOrigin.y - CGRectGetHeight(frame));
}
else { // UICollectionViewScrollDirectionHorizontal
frame.origin.x = MIN(MAX(contentOffset.x, frame.origin.x), nextHeaderOrigin.x - CGRectGetWidth(frame));
}
attributes.zIndex = 1024;
attributes.frame = frame;
}
return attributes;
}
- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForSupplementaryViewOfKind:kind atIndexPath:indexPath];
return attributes;
}
- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDisappearingSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForSupplementaryViewOfKind:kind atIndexPath:indexPath];
return attributes;
}
- (BOOL) shouldInvalidateLayoutForBoundsChange:(CGRect)newBound{
return YES;
}