iOS UICollectionView跳过单元格的数据

Question

When assigning data to my UICollectionViewCell it gets added but leaves a blank Cell between them.

When the UICollectionView is displayed I expect results to be:

[1] [2] [3] [4] and so on

But instead I get this:

[1] [ ] [2] [ ] [3] [ ] [4]

Code from viewDidLoad :

- (void) viewDidLoad {
    UICollectionViewFlowLayout *layout=[[UICollectionViewFlowLayout alloc] init];
    [layout setScrollDirection:UICollectionViewScrollDirectionHorizontal];

    _collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(10, 10, self.view.frame.size.width-20, 70) collectionViewLayout:layout];
    _collectionView.userInteractionEnabled = YES;
    _collectionView.alwaysBounceHorizontal = YES;
    _collectionView.multipleTouchEnabled = NO;
    [_collectionView setDataSource:self];
    [_collectionView setDelegate:self];
    [_collectionView setPagingEnabled:NO];
    [_collectionView setScrollEnabled:YES];
    [_collectionView registerClass:[CustomCell class] forCellWithReuseIdentifier:@"CustomCell"];
}

Code from cellForItemAtIndexPath :

- (CustomCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    CustomCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"CustomCell" forIndexPath:indexPath];
    cell.titleLabel.text = [NSString stringWithFormat:@"%d", indexPath.row]; //testing row

    return cell;
}

And my CustomCell.m :

- (id)initWithFrame:(CGRect)aRect
{
    self = [super initWithFrame:aRect];
    {
        titleLabel = [[UILabel alloc] initWithFrame:self.frame];

        [self addSubview:titleLabel];
    }
    return self;
}

Answer 1

You should try to implement one of these (if not, all) methods:

-(CGSize) collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{
-(CGFloat) collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;
-(CGFloat) collectionView:(UICollectionView *) collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section{

The UICollectionViewDelegateFlowLayout is responsible with the sizes and the spacing between cells in a UICollectionView. Find out more here .

Nevertheless, if you want to fully solve and find out which is the main problem, you should debug your views by pressing the 7th button on the Xcode's bottom bar(I have the 7.2 version). Here is a snapshot:

And this is how it should look the debugging:

Answer 2

Wow I could solve this!

I've logged the Subviews of the CustomCell and there is a bug I think when assigning the frame to UILabel .

Log for titleLabel = [[UILabel alloc] initWithFrame:self.frame] :

 App( "<UIView: 0x7b74cb00; frame = (0 0; 50 70); gestureRecognizers = <NSArray: 0x7b74d0b0>; layer = <CALayer: 0x7b74cbc0>>", "<UILabel: 0x7b74d0e0; frame = (0 0; 50 70); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7b74d1f0>>" ) App ( "<UIView: 0x7c954cf0; frame = (0 0; 50 70); gestureRecognizers = <NSArray: 0x7c919a10>; layer = <CALayer: 0x7c9f30e0>>", "<UILabel: 0x7c985bc0; frame = (55 0; 50 70); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7c952020>>" ) 

As you can see the frame of the UILabel gets pushed right.

Log for titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 50, 70)] :

 App ( "<UIView: 0x7c2a1f00; frame = (0 0; 50 70); gestureRecognizers = <NSArray: 0x7c2924f0>; layer = <CALayer: 0x7c2a4970>>", "<UILabel: 0x7c2a3c60; frame = (0 0; 50 70); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7c292520>>" ) App ( "<UIView: 0x7c2a3f30; frame = (0 0; 50 70); gestureRecognizers = <NSArray: 0x7c2a5ce0>; layer = <CALayer: 0x7c2a3ff0>>", "<UILabel: 0x7c2a5d10; frame = (0 0; 50 70); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7c2a5e20>>" ) 

Now the frame of the UILabel is exactly the same as the UICollectionViewCell respectively as the UIView .