How to add views between UICollectionViewCells in

问题:

I'm trying to add UIViews between my UICollectionViewCells in my UICollectionView and I don't know how I could do that. I'm trying to accomplish something like this:

I'll probably need to write a custom UICollectionViewLayout, but I don't really know where to start.

回答1:

I studied more of how UICollectionViewLayouts work and figured out how to solve it. I have an UICollectionReusableView subclass called OrangeView that will be positioned between my views, than I wrote an UICollectionViewFlowLayout subclass called CategoriesLayout that will deal with my layout.

Sorry for the big block of code, but here is how it looks like:

@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

I also wrote a category with some methods to check if an index path is the last in a line, in the last line or the last in a section:

@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

And this is the final result:

回答2:

If you're using sections and the layout is appropriate for it, you might use section headers and footers.

But based on your illustration, it looks like you just need to define the UICollectionViewCell to contain those views. So, where you register your class:

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

put those border images in the UICollectionView cell subclass (in the above case, "CollectionViewCell"). That seems like the easiest approach.

Here's one I use:

- (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;
}

回答3:

Looks like if your collectionView background was green and contentView white you could get the horizontals with a space between the cells minimumLineSpacing. The vertical gap would be the tricky part, but if you were creative with your contentView and set the minimumInteritemSpacing carefully you could get it.

回答4:

Wow. That's a lot of code in the other answers just for a separator line between rows..

This is how I solved it. First you'll need to add the line separator inside the cell. Make sure you keep dragging it making it wider than the actual cell width so if your cell width is 60p your separator line will be 70.

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

inside cellForItemAtIndexPath:

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;

If you want a separator at the end of the collection view but there's a chance that you won't get 4 cells at the last row you can add a simple Collection Reusable View as Footer.