UICollectionView estimatedItemSize - 最后一个单元格未对齐

Question

I want to make a usual horizontalScrolling flowLayout UICollectionView with estimatedItemSize and preferredLayoutAttributesFittingAttributes in cell. But there is something wrong with last cell. Any idea where is the issue? Project itself

@implementation RowCollectionView

- (instancetype) initWithFrame:(CGRect)frame collectionViewLayout:(UICollectionViewLayout *)layout
{
    if (self = [super initWithFrame:frame collectionViewLayout:layout])
    {
        [self configureRowCollectionView];
    }

    return self;
}

- (void) awakeFromNib
{
    [super awakeFromNib];

    [self configureRowCollectionView];
}

- (void) configureRowCollectionView
{
    self.backgroundColor = [UIColor lightGrayColor];

    self.dataSource = self;
    self.delegate = self;

    // Horizontal Direction
    UICollectionViewFlowLayout *flowLayout = (UICollectionViewFlowLayout *) self.collectionViewLayout;
    flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;

    // Estimated Item Size
    flowLayout.estimatedItemSize = CGSizeMake(self.bounds.size.height, self.bounds.size.height);


    [self registerClass:[RowCollectionViewCell class] forCellWithReuseIdentifier:NSStringFromClass([RowCollectionViewCell class])];
}

- (NSInteger) collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 10;
}

- (UICollectionViewCell *) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:NSStringFromClass([RowCollectionViewCell class]) forIndexPath:indexPath];

    cell.contentView.backgroundColor = [UIColor redColor];

    return cell;
}

@end

@implementation RowCollectionViewCell

- (UICollectionViewLayoutAttributes *) preferredLayoutAttributesFittingAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes
{
    [super preferredLayoutAttributesFittingAttributes:layoutAttributes];

    UICollectionViewLayoutAttributes *attributes = [layoutAttributes copy];

    attributes.size = CGSizeMake(80, 80);

    return attributes;
}

@end    

Answer 1

我面临一个类似的问题，通过使用委托方法--UICollectionViewDelegateFlowLayout的minimumInteritemSpacingForSectionAt-给出一个适当的最小项间距来解决问题。

Answer 2

You are setting estimatedItemSize in the init of view itself.

You need to set it in some controller.

Also,

If all of your cells are the same height, use the itemSize property, instead of this property, to specify the cell size instead.

Documentation: estimatedItemSize

Answer 3

there is a simple method to resolve this. You can add number of prototype cells to check the cell at required position. Once you find the issue at last cell . Check the cell insets in Inspector window.

Answer 4

You call super method but you did not use super returned layoutAttributes.

    [super preferredLayoutAttributesFittingAttributes:layoutAttributes];

You can try to print out original layoutAttributes vs super's layoutAttributes. Sometimes, you don't need to call super function.

Second, You can create custom flowlayout or set inset to let your cell align top. I did this in my project.

Answer 5

You can consider it a Suggestion. According to me the height of UICollectionView is more than UICollectionViewCell Height, thats why its happening. please make them equal them

Answer 6

自定义单元格大小必须与集合视图单元格大小相同，请检查。它可以为您解决问题。

Answer 7

I have done the similar small project (one raw (1*N) horizontal collection view), here is the github. I hope it would be helpful for your requirement.

https://github.com/texas16/HorizontalCollectionView

Answer 8

Had same problem and what fix it in my case was to make sure :

1. All cells height are equal.

2. The collectionView height is bigger then cell height + space between cells.