Add a pad to the first and last cell of a UICollectionView

Question

I subclass UICollectionViewFlowLayout to get a horizontal UICollectionView with swap-like behavior. It works great until the UICollectionViewCell is the first of the last cell. Images are attached below.

Do I need to override something in my UICollectionViewFlowLayout other than the following?

- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity
{
CGFloat offSetAdjustment = MAXFLOAT;
CGFloat horizontalCenter = (CGFloat) (proposedContentOffset.x + (self.collectionView.bounds.size.width / 2.0));

CGRect targetRect = CGRectMake(proposedContentOffset.x,
                               0.0,
                               self.collectionView.bounds.size.width,
                               self.collectionView.bounds.size.height);

NSArray *array = [self layoutAttributesForElementsInRect:targetRect];
for (UICollectionViewLayoutAttributes *layoutAttributes in array)
{
    if(layoutAttributes.representedElementCategory == UICollectionElementCategoryCell)
    {
        CGFloat itemHorizontalCenter = layoutAttributes.center.x;
        if (ABS(itemHorizontalCenter - horizontalCenter) < ABS(offSetAdjustment))
        {
            offSetAdjustment = itemHorizontalCenter - horizontalCenter;
        }
    }
}

CGFloat nextOffset = proposedContentOffset.x + offSetAdjustment;

do {
    proposedContentOffset.x = nextOffset;
    CGFloat deltaX = proposedContentOffset.x - self.collectionView.contentOffset.x;
    CGFloat velX = velocity.x;

    if(deltaX == 0.0 || velX == 0 || (velX > 0.0 && deltaX > 0.0) || (velX < 0.0 && deltaX < 0.0))
    {
        break;
    }

    if(velocity.x > 0.0)
    {
        nextOffset += [self snapStep];
    }
    else if(velocity.x < 0.0)
    {
        nextOffset -= [self snapStep];
    }
} while ([self isValidOffset:nextOffset]);

proposedContentOffset.y = 0.0;

return proposedContentOffset;
}
    - (BOOL)isValidOffset:(CGFloat)offset
{
    return (offset >= [self minContentOffset] && offset <= [self maxContentOffset]);
}

- (CGFloat)minContentOffset
{
  return -self.collectionView.contentInset.left;
}

- (CGFloat)maxContentOffset
{
    return [self minContentOffset] + self.collectionView.contentSize.width -      self.itemSize.width;
}

- (CGFloat)snapStep
{
return self.itemSize.width + self.minimumLineSpacing;
}

Any pointers / comments would be helpful.

Answer 1

You can set the space on the left and right to indent when setting the frame for the collection view.

or

cellForItemAtIndexPath, , , . .

contentInset collectionView.

,

UICollectionView *cv; // your collectionView

cv.contentInset = UIEdgeInsetsMake(0, 5, 0, 5);

UICollectionView contentInset , .

Answer 2

, . :

Answer 3

Swift 5:

viewDidLoad contentInset collectionView :

self.collectionView.contentInset = UIEdgeInsets(top: 0, left: 5, bottom: 0, right: 5);

Answer 4

simple UIEdgeInsets, , bellow.

-(UIEdgeInsets)collectionView:(UICollectionView*)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
  return UIEdgeInsetsMake(0,10,0,10); // top, left, bottom, right
}

here you can pass the value for the left space and right space for the first and last cell, you can also provide the minimum space between two cells through the following method

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section {
   return 5.0;
}

Answer 5

The accepted solution works, but if you enabled pagingEnabled, swapping the collection view does not work .

For me, the solution was to use:

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
    return UIEdgeInsets(top: 0, left: 16, bottom: 0, right: 16)
}