我在水平滚动的UICollectionView上有不同高度的单元格,它们似乎垂直均匀地分布单元格,在单元格之间留下空白空间,我想在顶部对齐它们并在每列底部有变量空白空间.
解决方法
我将提供的UICollectionViewFlowLayout扩展到了我的UICollectionView.以下压倒一切对我有用.
#import "TopAlignedCollectionViewFlowLayout.h"
const NSInteger kVerticalSpacing = 10;
@implementation TopAlignedCollectionViewFlowLayout
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
NSArray* attributesToReturn = [super layoutAttributesForElementsInRect:rect];
for (UICollectionViewLayoutAttributes* attributes in attributesToReturn) {
if (nil == attributes.representedElementKind) {
NSIndexPath* indexPath = attributes.indexPath;
attributes.frame = [self layoutAttributesForItemAtIndexPath:indexPath].frame;
}
}
return attributesToReturn;
}
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewLayoutAttributes* currentItemAttributes =
[super layoutAttributesForItemAtIndexPath:indexPath];
UIEdgeInsets sectionInset = [(UICollectionViewFlowLayout *)self.collectionView.collectionViewLayout sectionInset];
if (indexPath.item == 0) {
CGRect frame = currentItemAttributes.frame;
frame.origin.y = sectionInset.top;
currentItemAttributes.frame = frame;
return currentItemAttributes;
}
NSIndexPath* prevIoUsIndexPath = [NSIndexPath indexPathForItem:indexPath.item-1 inSection:indexPath.section];
CGRect prevIoUsFrame = [self layoutAttributesForItemAtIndexPath:prevIoUsIndexPath].frame;
CGFloat prevIoUsFrameRightPoint = prevIoUsFrame.origin.y + prevIoUsFrame.size.height + kVerticalSpacing;
CGRect currentFrame = currentItemAttributes.frame;
CGRect strecthedCurrentFrame = CGRectMake(currentFrame.origin.x,currentFrame.size.width,self.collectionView.frame.size.height
);
if (!CGRectIntersectsRect(prevIoUsFrame,strecthedCurrentFrame)) {
CGRect frame = currentItemAttributes.frame;
frame.origin.y = frame.origin.y = sectionInset.top;
currentItemAttributes.frame = frame;
return currentItemAttributes;
}
CGRect frame = currentItemAttributes.frame;
frame.origin.y = prevIoUsFrameRightPoint;
currentItemAttributes.frame = frame;
return currentItemAttributes;
}
@end
