如何确定UICollectionView flowLayout中单元格之间的间距

时间:2012-10-22 18:15:03

标签: iphone objective-c ios ipad uicollectionview

我有一个带流布局的UICollectionView,每个单元格都是一个正方形。如何确定每行上每个单元格之间的间距?我似乎找不到适合的设置。我看到nib文件中有一个min间距属性用于集合视图,但我将其设置为0并且单元格甚至没有粘贴。

enter image description here

还有其他想法吗?

12 个答案:

答案 0 :(得分:69)

更新:此答案的Swift版本:https://github.com/fanpyi/UICollectionViewLeftAlignedLayout-Swift


采取@matt's lead我修改了他的代码,以确保项目始终保持对齐。我发现如果一个项目本身就在一条线上,它将以流布局为中心。我做了以下更改来解决这个问题。

如果您的单元格宽度不同,则只会出现这种情况,这可能会导致如下所示的布局。由于UICollectionViewFlowLayout的行为,最后一行始终保持对齐,问题在于它们本身在任何行中但最后一行的项目。

我看到@ matt的代码。

enter image description here

在那个例子中,我们看到细胞如果它们自己最终在线上就会居中。下面的代码可确保您的收藏视图看起来像这样。

enter image description here

#import "CWDLeftAlignedCollectionViewFlowLayout.h"

const NSInteger kMaxCellSpacing = 9;

@implementation CWDLeftAlignedCollectionViewFlowLayout

- (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) { // first item of section
        CGRect frame = currentItemAttributes.frame;
        frame.origin.x = sectionInset.left; // first item of the section should always be left aligned
        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.x + previousFrame.size.width + kMaxCellSpacing;

    CGRect currentFrame = currentItemAttributes.frame;
    CGRect strecthedCurrentFrame = CGRectMake(0,
                                              currentFrame.origin.y,
                                              self.collectionView.frame.size.width,
                                              currentFrame.size.height);

    if (!CGRectIntersectsRect(previousFrame, strecthedCurrentFrame)) { // if current item is the first item on the line
        // the approach here is to take the current frame, left align it to the edge of the view
        // then stretch it the width of the collection view, if it intersects with the previous frame then that means it
        // is on the same line, otherwise it is on it's own new line
        CGRect frame = currentItemAttributes.frame;
        frame.origin.x = sectionInset.left; // first item on the line should always be left aligned
        currentItemAttributes.frame = frame;
        return currentItemAttributes;
    }

    CGRect frame = currentItemAttributes.frame;
    frame.origin.x = previousFrameRightPoint;
    currentItemAttributes.frame = frame;
    return currentItemAttributes;
}

@end

答案 1 :(得分:32)

要获得最大的interitem间距,请继承UICollectionViewFlowLayout并覆盖layoutAttributesForElementsInRect:layoutAttributesForItemAtIndexPath:

例如,一个常见的问题是:集合视图的行是左右对齐的,除了左对齐的最后一行。假设我们想要所有这些行是左对齐的,所以它们之间的空间就是10点。这是一个简单的方法(在你的UICollectionViewFlowLayout子类中):

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
    NSArray* arr = [super layoutAttributesForElementsInRect:rect];
    for (UICollectionViewLayoutAttributes* atts in arr) {
        if (nil == atts.representedElementKind) {
            NSIndexPath* ip = atts.indexPath;
            atts.frame = [self layoutAttributesForItemAtIndexPath:ip].frame;
        }
    }
    return arr;
}

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewLayoutAttributes* atts =
    [super layoutAttributesForItemAtIndexPath:indexPath];

    if (indexPath.item == 0) // degenerate case 1, first item of section
        return atts;

    NSIndexPath* ipPrev =
    [NSIndexPath indexPathForItem:indexPath.item-1 inSection:indexPath.section];

    CGRect fPrev = [self layoutAttributesForItemAtIndexPath:ipPrev].frame;
    CGFloat rightPrev = fPrev.origin.x + fPrev.size.width + 10;
    if (atts.frame.origin.x <= rightPrev) // degenerate case 2, first item of line
        return atts;

    CGRect f = atts.frame;
    f.origin.x = rightPrev;
    atts.frame = f;
    return atts;
}

这很容易的原因是我们并没有真正完成布局的繁重工作;我们正在利用UICollectionViewFlowLayout已经为我们完成的布局工作。它已经决定了每行中有多少项;如果你明白我的意思,我们只是阅读那些线条并将这些物品推到一起。

答案 2 :(得分:16)

有几件事需要考虑:

  1. 尝试更改IB中的最小间距,但将光标留在该字段中。 请注意,Xcode不会立即将文档标记为已更改。但是,当您单击其他字段时,Xcode会注意到文档已更改并在文件导航器中将其标记。因此,请务必在进行更改后选项卡或单击其他字段。

  2. 进行更改后保存storyboard / xib文件,并确保重建应用程序。不难错过这一步,然后你就会不知道为什么你的改变似乎没有任何效果。

  3. UICollectionViewFlowLayout具有minimumInteritemSpacing属性,这是您在IB中设置的属性。但是该集合的代表也可以拥有a method to determine the inter-item spacing。该方法胜过布局的属性,因此如果您在代理中实现它,您的布局属性将无法使用。

  4. 请记住,间距是最小间距。布局将使用该数字(无论是来自属性还是来自委托方法)作为最小的允许空间,但如果它在线上有剩余空间,则可以使用更大的空间。因此,例如,如果将最小间距设置为0,则可能仍会在项目之间看到一些像素。如果您想要更精确地控制项目间隔的方式,您应该使用不同的布局(可能是您自己创建的布局)。

答案 3 :(得分:4)

一点点数学就能更容易地解决这个问题。 Chris Wagner编写的代码非常糟糕,因为它调用了每个先前项目的布局属性。所以滚动的越多,它就越慢......

只需使用这样的模数(我也使用minimumInteritemSpacing值作为最大值):

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewLayoutAttributes* currentItemAttributes = [super layoutAttributesForItemAtIndexPath:indexPath];
    NSInteger numberOfItemsPerLine = floor([self collectionViewContentSize].width / [self itemSize].width);

    if (indexPath.item % numberOfItemsPerLine != 0)
    {
        NSInteger cellIndexInLine = (indexPath.item % numberOfItemsPerLine);

        CGRect itemFrame = [currentItemAttributes frame];
        itemFrame.origin.x = ([self itemSize].width * cellIndexInLine) + ([self minimumInteritemSpacing] * cellIndexInLine);
        currentItemAttributes.frame = itemFrame;
    }

    return currentItemAttributes;
}

答案 4 :(得分:3)

左对齐的简单方法是在UICollectionViewFlowLayout的子类中修改layoutAttributesForElementsInRect:

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSArray *allLayoutAttributes = [super layoutAttributesForElementsInRect:rect];
    CGRect prevFrame = CGRectMake(-FLT_MAX, -FLT_MAX, 0, 0);
    for (UICollectionViewLayoutAttributes *layoutAttributes in allLayoutAttributes)
    {
        //fix blur
        CGRect theFrame = CGRectIntegral(layoutAttributes.frame);

        //left justify
        if(prevFrame.origin.x > -FLT_MAX &&
           prevFrame.origin.y >= theFrame.origin.y &&
           prevFrame.origin.y <= theFrame.origin.y) //workaround for float == warning
        {
            theFrame.origin.x = prevFrame.origin.x +
                                prevFrame.size.width + 
                                EXACT_SPACE_BETWEEN_ITEMS;
        }
        prevFrame = theFrame;

        layoutAttributes.frame = theFrame;
    }
    return allLayoutAttributes;
}

答案 5 :(得分:2)

克里斯解决方案的快速版本。

class PazLeftAlignedCollectionViewFlowLayout : UICollectionViewFlowLayout {
    var maxCellSpacing = 14.0
    override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject]? {
        if var attributesToReturn = super.layoutAttributesForElementsInRect(rect) as? Array<UICollectionViewLayoutAttributes> {
            for attributes in attributesToReturn {
                if attributes.representedElementKind == nil {
                    let indexPath = attributes.indexPath
                    attributes.frame = self.layoutAttributesForItemAtIndexPath(indexPath).frame;
                }
            }
            return attributesToReturn;
        }
        return super.layoutAttributesForElementsInRect(rect)
    }

    override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes! {
        let currentItemAttributes = super.layoutAttributesForItemAtIndexPath(indexPath)

        if let collectionViewFlowLayout = self.collectionView?.collectionViewLayout as? UICollectionViewFlowLayout {
            let sectionInset = collectionViewFlowLayout.sectionInset
            if (indexPath.item == 0) { // first item of section
                var frame = currentItemAttributes.frame;
                frame.origin.x = sectionInset.left; // first item of the section should always be left aligned
                currentItemAttributes.frame = frame;

                return currentItemAttributes;
            }

            let previousIndexPath = NSIndexPath(forItem:indexPath.item-1, inSection:indexPath.section)
            let previousFrame = self.layoutAttributesForItemAtIndexPath(previousIndexPath).frame;
            let previousFrameRightPoint = Double(previousFrame.origin.x) + Double(previousFrame.size.width) + self.maxCellSpacing

            let currentFrame = currentItemAttributes.frame
            var width : CGFloat = 0.0
            if let collectionViewWidth = self.collectionView?.frame.size.width {
                width = collectionViewWidth
            }
            let strecthedCurrentFrame = CGRectMake(0,
                currentFrame.origin.y,
                width,
                currentFrame.size.height);

            if (!CGRectIntersectsRect(previousFrame, strecthedCurrentFrame)) { // if current item is the first item on the line
                // the approach here is to take the current frame, left align it to the edge of the view
                // then stretch it the width of the collection view, if it intersects with the previous frame then that means it
                // is on the same line, otherwise it is on it's own new line
                var frame = currentItemAttributes.frame;
                frame.origin.x = sectionInset.left; // first item on the line should always be left aligned
                currentItemAttributes.frame = frame;
                return currentItemAttributes;
            }

            var frame = currentItemAttributes.frame;
            frame.origin.x = CGFloat(previousFrameRightPoint)
            currentItemAttributes.frame = frame;
        }
        return currentItemAttributes;
    }
}

要使用它,请执行以下操作:

    override func viewDidLoad() {
    super.viewDidLoad()
    self.collectionView.collectionViewLayout = self.layout
}
var layout : PazLeftAlignedCollectionViewFlowLayout {
    var layout = PazLeftAlignedCollectionViewFlowLayout()
    layout.itemSize = CGSizeMake(220.0, 230.0)
    layout.minimumLineSpacing = 12.0
    return layout
}

答案 6 :(得分:2)

&#34;问题&#34;使用UICollectionViewFlowLayout是它对单元格应用对齐的对齐:行中的第一个单元格是左对齐的,行中的最后一个单元格是右对齐的,其间的所有其他单元格均匀分布,等于间距大于minimumInteritemSpacing

这篇文章已经有很多很好的答案可以通过继承UICollectionViewFlowLayout来解决这个问题。因此,您将获得一个对齐单元格左侧的布局。另一种以恒定间距分布细胞的有效解决方案是将细胞对齐正确

AlignedCollectionViewFlowLayout

我已经创建了一个UICollectionViewFlowLayout子类,它遵循mattChris Wagner建议的类似想法,可以对齐单元格

⬅︎

Left-aligned layout

➡︎ 正确

Right-aligned layout

您只需从此处下载,将布局文件添加到项目中,并将AlignedCollectionViewFlowLayout设置为您的收藏视图的布局类:
https://github.com/mischa-hildebrand/AlignedCollectionViewFlowLayout

它是如何工作的(对于左对齐的单元格):

 +---------+----------------------------------------------------------------+---------+
 |         |                                                                |         |
 |         |     +------------+                                             |         |
 |         |     |            |                                             |         |
 | section |- - -|- - - - - - |- - - - +---------------------+ - - - - - - -| section |
 |  inset  |     |intersection|        |                     |   line rect  |  inset  |
 |         |- - -|- - - - - - |- - - - +---------------------+ - - - - - - -|         |
 | (left)  |     |            |             current item                    | (right) |
 |         |     +------------+                                             |         |
 |         |     previous item                                              |         |
 +---------+----------------------------------------------------------------+---------+

这里的概念是检查索引 i 的当前单元格和索引 i-1 的前一个单元格是否占用相同的行。

  • 如果他们没有索引 i 的单元格是该行中最左边的单元格。
    →将单元格移动到集合视图的左边缘(不更改其垂直位置)。
  • 如果是这样,索引 i 的单元格不是该行中最左边的单元格。
    →获取上一个单元格的框架(索引 i-1 )并移动旁边的当前单元格。

对于右对齐的单元格......

...反之亦然,即您使用索引 i + 1 检查 next 单元格。

答案 7 :(得分:2)

从进化史中清除Swift解决方案:

  1. matt answer
  2. Chris Wagner lone items fix
  3. mokagio sectionInset and minimumInteritemSpacing improvement
  4. fanpyi Swift version
  5. 现在这里是我的简化版本:
  6. open class UICollectionViewLeftAlignedLayout: UICollectionViewFlowLayout {
        open override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
            return super.layoutAttributesForElements(in: rect)?.map { $0.representedElementKind == nil ? layoutAttributesForItem(at: $0.indexPath)! : $0 }
        }
    
        open override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
            guard let currentItemAttributes = super.layoutAttributesForItem(at: indexPath)?.copy() as? UICollectionViewLayoutAttributes,
                collectionView != nil else {
                // should never happen
                return nil
            }
    
            // if the current frame, once stretched to the full row intersects the previous frame then they are on the same row
            if indexPath.item != 0,
                let previousFrame = layoutAttributesForItem(at: IndexPath(item: indexPath.item - 1, section: indexPath.section))?.frame,
                currentItemAttributes.frame.intersects(CGRect(x: -.infinity, y: previousFrame.origin.y, width: .infinity, height: previousFrame.size.height)) {
                // the next item on a line
                currentItemAttributes.frame.origin.x = previousFrame.origin.x + previousFrame.size.width + evaluatedMinimumInteritemSpacingForSection(at: indexPath.section)
            } else {
                // the first item on a line
                currentItemAttributes.frame.origin.x = evaluatedSectionInsetForSection(at: indexPath.section).left
            }
            return currentItemAttributes
        }
    
        func evaluatedMinimumInteritemSpacingForSection(at section: NSInteger) -> CGFloat {
            return (collectionView?.delegate as? UICollectionViewDelegateFlowLayout)?.collectionView?(collectionView!, layout: self, minimumInteritemSpacingForSectionAt: section) ?? minimumInteritemSpacing
        }
    
        func evaluatedSectionInsetForSection(at index: NSInteger) -> UIEdgeInsets {
            return (collectionView?.delegate as? UICollectionViewDelegateFlowLayout)?.collectionView?(collectionView!, layout: self, insetForSectionAt: index) ?? sectionInset
        }
    }
    

    用法:项目之间的间距由代表collectionView (_:layout:minimumInteritemSpacingForSectionAt:)确定。

    我把它放在github https://github.com/Coeur/UICollectionViewLeftAlignedLayout上,我实际上添加了一个支持两个滚动方向(水平和垂直)的功能。

答案 8 :(得分:2)

您可以通过两种方式进行操作。

首先,在layoutAttributesForItem中进行一些修改,

通过上一个layoutAttributesForItem(at: IndexPath(item: indexPath.item - 1, section: indexPath.section))?.frame获取当前属性的布局。

  

layoutAttributesForItem(at :):此方法向集合视图提供按需布局信息。您需要重写它,并在请求的indexPath处返回该项目的布局属性。

其次,通过UICollectionViewLayoutAttributes(forCellWith: indexPath)新建一些属性,将它们布置在所需的位置。

而且数学要大一点,因为它执行了布局的繁重工作。

  

layoutAttributesForElements(in :):在此方法中,您需要返回给定矩形内所有项目的布局属性。将属性作为UICollectionViewLayoutAttributes数组返回到集合视图。


您可以选中My repo

  • 您可以将项目保持对齐状态

  • 您可以将项目右对齐

  • 您可以将项目对齐并反转

答案 9 :(得分:1)

基于Chris Wagner的回答,为感兴趣的人提供了一个更清洁的快速版本:

class AlignLeftFlowLayout: UICollectionViewFlowLayout {

    var maximumCellSpacing = CGFloat(9.0)

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

        for attributes in attributesToReturn ?? [] {
            if attributes.representedElementKind == nil {
                attributes.frame = self.layoutAttributesForItemAtIndexPath(attributes.indexPath).frame
            }
        }

        return attributesToReturn
    }

    override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes! {
        let curAttributes = super.layoutAttributesForItemAtIndexPath(indexPath)
        let sectionInset = (self.collectionView?.collectionViewLayout as UICollectionViewFlowLayout).sectionInset

        if indexPath.item == 0 {
            let f = curAttributes.frame
            curAttributes.frame = CGRectMake(sectionInset.left, f.origin.y, f.size.width, f.size.height)
            return curAttributes
        }

        let prevIndexPath = NSIndexPath(forItem: indexPath.item-1, inSection: indexPath.section)
        let prevFrame = self.layoutAttributesForItemAtIndexPath(prevIndexPath).frame
        let prevFrameRightPoint = prevFrame.origin.x + prevFrame.size.width + maximumCellSpacing

        let curFrame = curAttributes.frame
        let stretchedCurFrame = CGRectMake(0, curFrame.origin.y, self.collectionView!.frame.size.width, curFrame.size.height)

        if CGRectIntersectsRect(prevFrame, stretchedCurFrame) {
            curAttributes.frame = CGRectMake(prevFrameRightPoint, curFrame.origin.y, curFrame.size.width, curFrame.size.height)
        } else {
            curAttributes.frame = CGRectMake(sectionInset.left, curFrame.origin.y, curFrame.size.width, curFrame.size.height)
        }

        return curAttributes
    }
}

答案 10 :(得分:0)

这里是NSCollectionViewFlowLayout

class LeftAlignedCollectionViewFlowLayout: NSCollectionViewFlowLayout {

    var maximumCellSpacing = CGFloat(2.0)

    override func layoutAttributesForElementsInRect(rect: NSRect) -> [NSCollectionViewLayoutAttributes] {

        let attributesToReturn = super.layoutAttributesForElementsInRect(rect)

        for attributes in attributesToReturn ?? [] {
            if attributes.representedElementKind == nil {
                attributes.frame = self.layoutAttributesForItemAtIndexPath(attributes.indexPath!)!.frame
            }
        }
        return attributesToReturn
    }

    override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> NSCollectionViewLayoutAttributes? {

        let curAttributes = super.layoutAttributesForItemAtIndexPath(indexPath)
        let sectionInset = (self.collectionView?.collectionViewLayout as! NSCollectionViewFlowLayout).sectionInset

        if indexPath.item == 0 {
            let f = curAttributes!.frame
            curAttributes!.frame = CGRectMake(sectionInset.left, f.origin.y, f.size.width, f.size.height)
            return curAttributes
        }

        let prevIndexPath = NSIndexPath(forItem: indexPath.item-1, inSection: indexPath.section)
        let prevFrame = self.layoutAttributesForItemAtIndexPath(prevIndexPath)!.frame
        let prevFrameRightPoint = prevFrame.origin.x + prevFrame.size.width + maximumCellSpacing

        let curFrame = curAttributes!.frame
        let stretchedCurFrame = CGRectMake(0, curFrame.origin.y, self.collectionView!.frame.size.width, curFrame.size.height)

        if CGRectIntersectsRect(prevFrame, stretchedCurFrame) {
            curAttributes!.frame = CGRectMake(prevFrameRightPoint, curFrame.origin.y, curFrame.size.width, curFrame.size.height)
        } else {
            curAttributes!.frame = CGRectMake(sectionInset.left, curFrame.origin.y, curFrame.size.width, curFrame.size.height)
        }

        return curAttributes
    }
}

答案 11 :(得分:-1)

基于mokagio的快速版本:https://github.com/fanpyi/UICollectionViewLeftAlignedLayout-Swift

class UICollectionViewLeftAlignedLayout: UICollectionViewFlowLayout {
    override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        let attributesToReturn = super.layoutAttributesForElementsInRect(rect)
        if let attributesToReturn = attributesToReturn {
            for attributes in attributesToReturn {
                if attributes.representedElementKind == nil {
                    let indexpath = attributes.indexPath
                    if let attr = layoutAttributesForItemAtIndexPath(indexpath) {
                        attributes.frame = attr.frame
                    }

                }
            }
        }
        return attributesToReturn
    }

    override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
        if  let currentItemAttributes = super.layoutAttributesForItemAtIndexPath(indexPath){
            let sectionInset = self.evaluatedSectionInsetForItemAtIndex(indexPath.section)
            let  isFirstItemInSection = indexPath.item == 0;
            let  layoutWidth = CGRectGetWidth(self.collectionView!.frame) - sectionInset.left - sectionInset.right;

            if (isFirstItemInSection) {
                currentItemAttributes.leftAlignFrameWithSectionInset(sectionInset)
                return currentItemAttributes
            }

            let  previousIndexPath = NSIndexPath(forItem: indexPath.item - 1, inSection: indexPath.section)

            let previousFrame = layoutAttributesForItemAtIndexPath(previousIndexPath)?.frame ?? CGRectZero
            let  previousFrameRightPoint = previousFrame.origin.x + previousFrame.width
            let currentFrame = currentItemAttributes.frame;
            let  strecthedCurrentFrame = CGRectMake(sectionInset.left,
                currentFrame.origin.y,
                layoutWidth,
                currentFrame.size.height)
            // if the current frame, once left aligned to the left and stretched to the full collection view
            // widht intersects the previous frame then they are on the same line
            let  isFirstItemInRow = !CGRectIntersectsRect(previousFrame, strecthedCurrentFrame)

            if (isFirstItemInRow) {
                // make sure the first item on a line is left aligned
                currentItemAttributes.leftAlignFrameWithSectionInset(sectionInset)
                return currentItemAttributes
            }

            var frame = currentItemAttributes.frame;
            frame.origin.x = previousFrameRightPoint + evaluatedMinimumInteritemSpacingForSectionAtIndex(indexPath.section)
            currentItemAttributes.frame = frame;
            return currentItemAttributes;

        }
        return nil
    }
    func evaluatedMinimumInteritemSpacingForSectionAtIndex(sectionIndex:Int) -> CGFloat {
        if let delegate = self.collectionView?.delegate as? UICollectionViewDelegateFlowLayout {
            if delegate.respondsToSelector("collectionView:layout:minimumInteritemSpacingForSectionAtIndex:") {
                return delegate.collectionView!(self.collectionView!, layout: self, minimumInteritemSpacingForSectionAtIndex: sectionIndex)

            }
        }
        return self.minimumInteritemSpacing

    }
    func evaluatedSectionInsetForItemAtIndex(index: Int) ->UIEdgeInsets {
        if let delegate = self.collectionView?.delegate as? UICollectionViewDelegateFlowLayout {
            if  delegate.respondsToSelector("collectionView:layout:insetForSectionAtIndex:") {
                return delegate.collectionView!(self.collectionView!, layout: self, insetForSectionAtIndex: index)
            }
        }
        return self.sectionInset
    }
}