请注意属性名minimumInterItemSpacing。这将是项目之间的最小间距，而不是精确的间距。如果你设置minimumInterItemSpacing为某个值，你可以确保spacing不会小于该值。但有机会获得更高的价值。

实际上，项目之间的间距取决于几个因素itemSize和sectionInset。集合视图根据这些值动态放置内容。所以你不能保证精确的间距。你应该用sectionInset和minimumInterItemSpacing做一些试错。

我尝试了iago849的答案，它起作用了。

斯威夫特4

open override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
    guard let answer = super.layoutAttributesForElements(in: rect) else {
        return nil
    }
    let count = answer.count
    for i in 1..<count {
        let currentLayoutAttributes = answer[i]
        let prevLayoutAttributes = answer[i-1]
        let origin = prevLayoutAttributes.frame.maxX
        if (origin + CGFloat(spacing) + currentLayoutAttributes.frame.size.width) < self.collectionViewContentSize.width && currentLayoutAttributes.frame.origin.x > prevLayoutAttributes.frame.origin.x {
            var frame = currentLayoutAttributes.frame
            frame.origin.x = origin + CGFloat(spacing)
            currentLayoutAttributes.frame = frame
        }
    }
    return answer
}

这是github项目的链接。 https://github.com/vishalwaka/MultiTags

使用水平流布局，我也得到了10点之间的单元格间距。为了移除间距，我需要将minimumlinespespaces和minimumInterItemSpacing设置为零。

UICollectionViewFlowLayout *flow = [[UICollectionViewFlowLayout alloc] init];
flow.itemSize = CGSizeMake(cellWidth, cellHeight);
flow.scrollDirection = UICollectionViewScrollDirectionHorizontal;
flow.minimumInteritemSpacing = 0;
flow.minimumLineSpacing = 0;

此外，如果所有单元格大小相同，直接在流布局上设置属性比使用委托方法更简单、更有效。

Swift 3版本

简单地创建一个UICollectionViewFlowLayout子类并粘贴这个方法。

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

        for i in 1..<answer.count {
            let currentAttributes = answer[i]
            let previousAttributes = answer[i - 1]

            let maximumSpacing: CGFloat = 8
            let origin = previousAttributes.frame.maxX

            if (origin + maximumSpacing + currentAttributes.frame.size.width < self.collectionViewContentSize.width && currentAttributes.frame.origin.x > previousAttributes.frame.origin.x) {
                var frame = currentAttributes.frame
                frame.origin.x = origin + maximumSpacing
                currentAttributes.frame = frame
            }
        }

        return answer
}

上面vojtech-vrbka的解决方案是正确的，但它会触发一个警告:

警告:UICollectionViewFlowLayout缓存的帧不匹配索引路径-缓存值:这可能是因为流布局子类layout是修改UICollectionViewFlowLayout返回的属性而没有复制它们

下面的代码应该修复它:

class CustomViewFlowLayout : UICollectionViewFlowLayout {

   let cellSpacing:CGFloat = 4

   override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
       let original = super.layoutAttributesForElementsInRect(rect)

       if let original = original {
           let attributes = NSArray.init(array: original, copyItems: true) as! [UICollectionViewLayoutAttributes]

           for (index, attribute) in attributes.enumerate() {
                if index == 0 { continue }
                let prevLayoutAttributes = attributes[index - 1]
                let origin = CGRectGetMaxX(prevLayoutAttributes.frame)
                if(origin + cellSpacing + attribute.frame.size.width < self.collectionViewContentSize().width) {
                    attribute.frame.origin.x = origin + cellSpacing
                }
            }
            return attributes
       }
       return nil
   }
}

试试这个方法:

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView
                    layout:(UICollectionViewLayout*)collectionViewLayout
    insetForSectionAtIndex:(NSInteger)section {

    UIEdgeInsets insets = UIEdgeInsetsMake(?, ?, ?, ?);

    return insets;
}