Question

我在水平滚动UICollectionView上有不同高度的单元格，看起来是垂直均匀地分布单元格，在单元格之间留下空白空间，我想顶部对齐它们并在底部有可变的空白空间每列。

Answer 1

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,
                                              0,
                                              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

Answer 2

我把它移植到Xamarin / MonoTouch我的项目，并认为它可能有用

public class TopAlignedCollectionViewFlowLayout : UICollectionViewFlowLayout
{
    const int VerticalSpacing = 10;

    public override UICollectionViewLayoutAttributes[] LayoutAttributesForElementsInRect(RectangleF rect)
    {
        var attributesToReturn = base.LayoutAttributesForElementsInRect(rect);
        foreach (UICollectionViewLayoutAttributes attributes in attributesToReturn)
        {
            if (attributes.RepresentedElementKind == null)
            {
                var indexPath = attributes.IndexPath;
                attributes.Frame = this.LayoutAttributesForItem(indexPath).Frame;
            }
        }
        return attributesToReturn;
    }

    public override UICollectionViewLayoutAttributes LayoutAttributesForItem(NSIndexPath indexPath)
    {
        var currentItemAttributes = base.LayoutAttributesForItem(indexPath);
        UIEdgeInsets sectionInset = ((UICollectionViewFlowLayout) this.CollectionView.CollectionViewLayout).SectionInset;

        if (indexPath.Item == 0)
        {
            var frame1 = currentItemAttributes.Frame;
            frame1.Y = sectionInset.Top;
            currentItemAttributes.Frame = frame1;

            return currentItemAttributes;
        }

        var previousIndexPath = NSIndexPath.FromItemSection(indexPath.Item - 1, indexPath.Section);
        var previousFrame = this.LayoutAttributesForItem(previousIndexPath).Frame;
        var previousFrameRightPoint = previousFrame.Y + previousFrame.Size.Height + VerticalSpacing;
        var currentFrame = currentItemAttributes.Frame;
        var strecthedCurrentFrame = new RectangleF(currentFrame.X, 0, currentFrame.Size.Width, this.CollectionView.Frame.Size.Height);
        if (!previousFrame.IntersectsWith(strecthedCurrentFrame))
        {
            var frame = currentItemAttributes.Frame;
            frame.Y = frame.Y = sectionInset.Top;
            currentItemAttributes.Frame = frame;
            return currentItemAttributes;
        }
        RectangleF frame2 = currentItemAttributes.Frame;
        frame2.Y = previousFrameRightPoint;
        currentItemAttributes.Frame = frame2;
        return currentItemAttributes;
    }

}

Answer 3

我想你正在使用UICollectionViewFlowLayout来布局你的单元格。我不认为你可以用流布局做到这一点。您可能必须编写UICollectionViewLayout的自定义子类来对齐每个单元格的上边缘。

这不是一个非常漂亮的解决方案，但是如何强制所有单元格大小相同并在单元格中设置约束以使内容与顶部对齐？这可以模拟你想要的外观而不必继承UICollectionViewLayout。

如何在UICollectionView中垂直对齐UICollectionViewCells？

3 个答案: