支持第一个问题。我试图在UICollectionView上获得5px的间距，但这并不奏效，以及UIEdgeInsetsMake(0,0,0,0)…

在UITableView中，我可以通过直接指定一行中的x,y坐标来做到这一点。

这是我的UICollectionView代码:

#pragma mark collection view cell layout / size
- (CGSize)collectionView:(UICollectionView*)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    return [self getCellSize:indexPath];  // will be w120xh100 or w190x100
    // if the width is higher, only one image will be shown in a line
}

#pragma mark collection view cell paddings
- (UIEdgeInsets)collectionView:(UICollectionView*)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
    return UIEdgeInsetsMake(0, 0, 0, 0); // top, left, bottom, right
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section {

    return 5.0;
}

更新:用下面的代码解决了我的问题。

ViewController。m

#import "ViewController.h"
#import "MagazineCell.h" // created just the default class. 

static NSString * const cellID = @"cellID";

@interface ViewController ()

@end

@implementation ViewController

#pragma mark - Collection view
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 30;
}

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    MagazineCell *mCell = (MagazineCell *)[collectionView dequeueReusableCellWithReuseIdentifier:cellID forIndexPath:indexPath];

    mCell.backgroundColor = [UIColor lightGrayColor];

    return mCell;
}

#pragma mark Collection view layout things
// Layout: Set cell size
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {

    NSLog(@"SETTING SIZE FOR ITEM AT INDEX %d", indexPath.row);
    CGSize mElementSize = CGSizeMake(104, 104);
    return mElementSize;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section {
    return 2.0;
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section {
    return 2.0;
}

// Layout: Set Edges
- (UIEdgeInsets)collectionView:
(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
   // return UIEdgeInsetsMake(0,8,0,8);  // top, left, bottom, right
    return UIEdgeInsetsMake(0,0,0,0);  // top, left, bottom, right
}

@end

试试这个方法:

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

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

    return insets;
}

我有一个水平的UICollectionView和子类化的UICollectionViewFlowLayout。集合视图具有较大的单元格，并且每次只显示一行单元格，并且集合视图适合屏幕的宽度。

我尝试了iago849的答案，它起作用了，但后来我发现我甚至不需要他的答案。出于某种原因，设置minimumInterItemSpacing没有任何作用。我的项目/单元格之间的间距可以完全由minimumlinespace控制。

不知道为什么会这样，但确实有效。

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

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。

投票的答案(以及快速版本)有一个小问题:右边会有一个很大的空格。

这是因为流布局是定制的，以使单元格间距精确，具有浮动左行为。

我的解决方案是操纵部分插入，使部分是对齐中心，但间距是完全指定的。

在下面的截图中，项目/行间距正好是8pt，而左右插入部分将大于8pt(使其居中对齐):

这样的Swift代码:

private let minItemSpacing: CGFloat = 8
private let itemWidth: CGFloat      = 100
private let headerHeight: CGFloat   = 32

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

    // Create our custom flow layout that evenly space out the items, and have them in the center
    let layout = UICollectionViewFlowLayout()
    layout.itemSize = CGSize(width: itemWidth, height: itemWidth)
    layout.minimumInteritemSpacing = minItemSpacing
    layout.minimumLineSpacing = minItemSpacing
    layout.headerReferenceSize = CGSize(width: 0, height: headerHeight)

    // Find n, where n is the number of item that can fit into the collection view
    var n: CGFloat = 1
    let containerWidth = collectionView.bounds.width
    while true {
        let nextN = n + 1
        let totalWidth = (nextN*itemWidth) + (nextN-1)*minItemSpacing
        if totalWidth > containerWidth {
            break
        } else {
            n = nextN
        }
    }

    // Calculate the section inset for left and right. 
    // Setting this section inset will manipulate the items such that they will all be aligned horizontally center.
    let inset = max(minItemSpacing, floor( (containerWidth - (n*itemWidth) - (n-1)*minItemSpacing) / 2 ) )
    layout.sectionInset = UIEdgeInsets(top: minItemSpacing, left: inset, bottom: minItemSpacing, right: inset)

    collectionView.collectionViewLayout = layout
}