如何在UICollectionView中的UICollectionViewCells之间添加视图？

Question

我正在尝试UIView在我UICollectionViewCell的s之间添加s UICollectionView而我不知道如何做到这一点.我正在努力完成这样的事情:

我可能需要写一个自定义UICollectionViewLayout,但我真的不知道从哪里开始.

Answer 1

我研究了更多如何UICollectionViewLayout工作并想出如何解决它.我有一个UICollectionReusableView被调用的子类OrangeView,它将位于我的视图之间,而不是我编写了一个UICollectionViewFlowLayout子类CategoriesLayout来处理我的布局.

很抱歉代码的大块,但这是它的样子:

@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否是行中的最后一行,最后一行或部分中的最后一行:

@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: