CODEWITHSUNDEEP
iosobjective-cuicollectionview
Evgeniy Kleban
Evgeniy Kleban

Reputation: 6940

Uicollectionview weird gap

I have collection view with custom flow layout and i wonder why i have extra space like that (right side):

enter image description here

It may hard to notice here, though, but you may see gray gap between right side and cell.

Here is how i override standard collection view flow layout to remove horizontals gaps:

@implementation CalendarFlowLayout

- (NSArray *) layoutAttributesForElementsInRect:(CGRect)rect {
    NSArray *answer = [super layoutAttributesForElementsInRect:rect];
    NSLog(@"layout blck passed");
    for(int i = 1; i < [answer count]; ++i) {
        UICollectionViewLayoutAttributes *currentLayoutAttributes = answer[i];
        UICollectionViewLayoutAttributes *prevLayoutAttributes = answer[i - 1];
        NSInteger maximumSpacing = 0;
        NSInteger origin = CGRectGetMaxX(prevLayoutAttributes.frame);

        if(origin + maximumSpacing + currentLayoutAttributes.frame.size.width < self.collectionViewContentSize.width) {
            CGRect frame = currentLayoutAttributes.frame;
            frame.origin.x = origin + maximumSpacing;
            currentLayoutAttributes.frame = frame;
        }
    }
    return answer;
}

@end

Cell size calculated as follow:

- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(UICollectionViewLayout *)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath{


    return CGSizeMake(SCREEN_WIDTH/7, (SCREEN_HEIGHT-NAVBAR_HEIGHT-STATUS_BAR_HEIGHT)/6);
}

Those macros above look like that:

#define SCREEN_WIDTH  [[UIScreen mainScreen] bounds].size.width

It has been tested and it return correct output.

Also, if i set width to SCREEN_WIDTH/3, there is will be no gap.

How to remove it? Why is that happen?

Upvotes: 0

Views: 92

Answers (2)

ddb
ddb

Reputation: 2435

The problem is that the width of the cell (eg. SCREEN_WIDTH/3) is not a divisor of SCREEN_WIDTH. Correct divisors of SCREEN_WIDTH (375, as you said in comments) are 3, 5, 25 and 125 (125*3=375).

But As there are different screen size among all iOS devices, I think you should manage the problem differently. For example, you should choose a specific cell width and try to center the collection view in its container, so the extra-space will always be divided on both left and right side of the collection view.

Upvotes: 1

Owen Hartnett
Owen Hartnett

Reputation: 5935

375 / 3 = 125

375 / 7 = 53.57142857142857

You can't really light a half a pixel, so it is probably rounding down, leaving you with a gap. Make sure your size is a multiple of your subview size (or add a pixel to the rightmost object if it's not).

Upvotes: 2

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