如何在 UICollectionView 中的 UICollectionViewCells 之间添加视图？

Question

我正在尝试在UICollectionView 中的UICollectionViewCells 之间添加UIViews，但我不知道该怎么做。我正在尝试完成这样的事情：

我可能需要编写一个自定义的UICollectionViewLayout，但我真的不知道从哪里开始。

Answer 1

我更多地研究了UICollectionViewLayouts 的工作原理，并想出了如何解决它。我有一个名为OrangeView 的UICollectionReusableView 子类，它将位于我的视图之间，而不是我编写了一个名为CategoriesLayout 的UICollectionViewFlowLayout 子类来处理我的布局。

抱歉，代码块很大，但它是这样的：

@implementation CategoriesLayout

- (void)prepareLayout {
    // Registers my decoration views.
    [self registerClass:[OrangeView class] forDecorationViewOfKind:@"Vertical"];
    [self registerClass:[OrangeView class] forDecorationViewOfKind:@"Horizontal"];
}

- (UICollectionViewLayoutAttributes *)layoutAttributesForDecorationViewOfKind:(NSString *)decorationViewKind atIndexPath:(NSIndexPath *)indexPath {
    // Prepare some variables.
    NSIndexPath *nextIndexPath = [NSIndexPath indexPathForItem:indexPath.row+1 inSection:indexPath.section];

    UICollectionViewLayoutAttributes *cellAttributes = [self layoutAttributesForItemAtIndexPath:indexPath];
    UICollectionViewLayoutAttributes *nextCellAttributes = [self layoutAttributesForItemAtIndexPath:nextIndexPath];

    UICollectionViewLayoutAttributes *layoutAttributes = [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:decorationViewKind withIndexPath:indexPath];

    CGRect baseFrame = cellAttributes.frame;
    CGRect nextFrame = nextCellAttributes.frame;

    CGFloat strokeWidth = 4;
    CGFloat spaceToNextItem = 0;
    if (nextFrame.origin.y == baseFrame.origin.y)
        spaceToNextItem = (nextFrame.origin.x - baseFrame.origin.x - baseFrame.size.width);

    if ([decorationViewKind isEqualToString:@"Vertical"]) {
        CGFloat padding = 10;

        // Positions the vertical line for this item.
        CGFloat x = baseFrame.origin.x + baseFrame.size.width + (spaceToNextItem - strokeWidth)/2;
        layoutAttributes.frame = CGRectMake(x,
                                            baseFrame.origin.y + padding,
                                            strokeWidth,
                                            baseFrame.size.height - padding*2);
    } else {
        // Positions the horizontal line for this item.
        layoutAttributes.frame = CGRectMake(baseFrame.origin.x,
                                            baseFrame.origin.y + baseFrame.size.height,
                                            baseFrame.size.width + spaceToNextItem,
                                            strokeWidth);
    }

    layoutAttributes.zIndex = -1;
    return layoutAttributes;
}

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
    NSArray *baseLayoutAttributes = [super layoutAttributesForElementsInRect:rect];
    NSMutableArray * layoutAttributes = [baseLayoutAttributes mutableCopy];

    for (UICollectionViewLayoutAttributes *thisLayoutItem in baseLayoutAttributes) {
        if (thisLayoutItem.representedElementCategory == UICollectionElementCategoryCell) {
            // Adds vertical lines when the item isn't the last in a section or in line.
            if (!([self indexPathLastInSection:thisLayoutItem.indexPath] ||
                  [self indexPathLastInLine:thisLayoutItem.indexPath])) {
                UICollectionViewLayoutAttributes *newLayoutItem = [self layoutAttributesForDecorationViewOfKind:@"Vertical" atIndexPath:thisLayoutItem.indexPath];
                [layoutAttributes addObject:newLayoutItem];
            }

            // Adds horizontal lines when the item isn't in the last line.
            if (![self indexPathInLastLine:thisLayoutItem.indexPath]) {
                UICollectionViewLayoutAttributes *newHorizontalLayoutItem = [self layoutAttributesForDecorationViewOfKind:@"Horizontal" atIndexPath:thisLayoutItem.indexPath];
                [layoutAttributes addObject:newHorizontalLayoutItem];
            }
        }
    }

    return layoutAttributes;
}

@end

我还编写了一个类别，其中包含一些方法来检查索引路径是在一行中的最后一个、在最后一行还是在一个节中的最后一个：

@implementation UICollectionViewFlowLayout (Helpers)

- (BOOL)indexPathLastInSection:(NSIndexPath *)indexPath {
    NSInteger lastItem = [self.collectionView.dataSource collectionView:self.collectionView numberOfItemsInSection:indexPath.section] -1;
    return  lastItem == indexPath.row;
}

- (BOOL)indexPathInLastLine:(NSIndexPath *)indexPath {
    NSInteger lastItemRow = [self.collectionView.dataSource collectionView:self.collectionView numberOfItemsInSection:indexPath.section] -1;
    NSIndexPath *lastItem = [NSIndexPath indexPathForItem:lastItemRow inSection:indexPath.section];
    UICollectionViewLayoutAttributes *lastItemAttributes = [self layoutAttributesForItemAtIndexPath:lastItem];
    UICollectionViewLayoutAttributes *thisItemAttributes = [self layoutAttributesForItemAtIndexPath:indexPath];

    return lastItemAttributes.frame.origin.y == thisItemAttributes.frame.origin.y;
}

- (BOOL)indexPathLastInLine:(NSIndexPath *)indexPath {
    NSIndexPath *nextIndexPath = [NSIndexPath indexPathForItem:indexPath.row+1 inSection:indexPath.section];

    UICollectionViewLayoutAttributes *cellAttributes = [self layoutAttributesForItemAtIndexPath:indexPath];
    UICollectionViewLayoutAttributes *nextCellAttributes = [self layoutAttributesForItemAtIndexPath:nextIndexPath];

    return !(cellAttributes.frame.origin.y == nextCellAttributes.frame.origin.y);
}

@end

这是最终的结果：

Answer 2

如果您正在使用节并且布局适合它，则可以使用节页眉和页脚。

但根据您的说明，您似乎只需要定义 UICollectionViewCell 即可包含这些视图。所以，你在哪里注册你的班级：

[collectionView registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:@"Cell"];

将这些边框图像放在 UICollectionView 单元子类中（在上面的例子中，“CollectionViewCell”）。这似乎是最简单的方法。

这是我使用的一个：

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self)
    {
        self.restorationIdentifier = @"Cell";
        self.backgroundColor = [UIColor clearColor];
        self.autoresizingMask = UIViewAutoresizingNone;
        const CGFloat borderWidth = 3.0f;
        UIView *bgView = [[UIView alloc] initWithFrame:frame];
        bgView.layer.borderColor = [UIColor blackColor].CGColor;
        bgView.layer.borderWidth = borderWidth;
        bgView.layer.cornerRadius = 6.0f;
        self.selectedBackgroundView = bgView;
    }
    return self;
}

Answer 3

看起来如果您的 collectionView 背景是绿色而 contentView 是白色的，您可以获得水平方向，单元格 minimumLineSpacing 之间有一个空格。垂直间隙将是棘手的部分，但如果您对 contentView 有创意并仔细设置minimumInteritemSpacing，您可以得到它。

Answer 4

哇。其他答案中有很多代码只是用于行之间的分隔线..

我就是这样解决的。首先，您需要在单元格内添加行分隔符。确保您一直拖动它，使其比实际单元格宽度更宽，因此如果您的单元格宽度为 60p，则分隔线将为 70。

@implementation CollectionViewController
{
    NSArray *test;
    int currentLocInRow;
}

在cellForItemAtIndexPath内：

if((indexPath.row+1) % 4 == 0)
    {
        cell.clipsToBounds = YES;
    }
    else
    {
        cell.clipsToBounds = NO;
    }
    currentLocInRow++;

    if([test count] - indexPath.row+1 < 4 - currentLocInRow)
    {
        cell.lineSeparator.alpha = 0;
    }
    else
    {
        cell.lineSeparator.alpha = 1;
    }
    if(currentLocInRow==4)currentLocInRow=0;

如果您想在集合视图的末尾添加一个分隔符，但最后一行可能没有 4 个单元格，您可以添加一个简单的集合可重用视图作为页脚。