自定义UIView中的UICollectionView

Question

我正在尝试使用UICollectionView制作自定义工具栏。

我想子类化UIView并将集合视图作为子子视图。

我使用的是标准流程布局，如果将集合视图添加到视图控制器中，则一切工作正常。

当我将UICollectionview添加到MY子类视图时，所有这些都将停止正常工作。这些项目首先出现在视图外部，我必须向下滚动才能看到它们。项目开始之前似乎要添加一行空白。

当我在UIView子类内的collectionview上调用contentSize时，由于某种原因它会返回-20的高度。

我将工具集实例指向直接在视图控制器视图中托管的CollectionView的数据源，这样就可以排除代码差异。我在想，我可能会错过一些与UIView生命周期事件有关的细微问题？

这是代码：

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}


-(void)updateConstraints
{

    [super updateConstraints];

    UIView* view = _collectionView;


    [self addConstraint:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:view.superview attribute:NSLayoutAttributeTop multiplier:1 constant:0]];
    [self addConstraint:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:view.superview attribute:NSLayoutAttributeBottom multiplier:1 constant:0]];

    [self addConstraint:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:view.superview attribute:NSLayoutAttributeLeading multiplier:1 constant:0]];
    [self addConstraint:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:view.superview attribute:NSLayoutAttributeTrailing multiplier:1 constant:0]];
}

-(void)layoutSubviews
{
    [super layoutSubviews];

    [_collectionView reloadData];
}

+(BOOL)requiresConstraintBasedLayout
{
    return YES;
}


-(id)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super initWithCoder:aDecoder])
    {
        _itemsVisibleAtOnce = 5;


     //   dispatch_async(dispatch_get_main_queue(), ^{
            UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];
          //  layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
            UICollectionView* collectionView = [[UICollectionView alloc] initWithFrame:self.bounds collectionViewLayout:layout];
            _collectionView = collectionView;


            [self.collectionView registerNib:[UINib nibWithNibName:@"OSButtonBarCell" bundle:nil] forCellWithReuseIdentifier:REUSUE_OS_TAB_CELL];


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


            _collectionView.translatesAutoresizingMaskIntoConstraints = NO;
           [self addSubview:_collectionView];

           // [self invalidateIntrinsicContentSize];

        [self setNeedsUpdateConstraints];




       // });

    }

    return self;
}




/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
}
*/

-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSUInteger numItemsHorizontal = [self collectionView:collectionView numberOfItemsInSection:indexPath.section];

    if (_itemsVisibleAtOnce < numItemsHorizontal)
    {
        numItemsHorizontal = _itemsVisibleAtOnce;
    }

    CGFloat itemWidth = collectionView.bounds.size.width / numItemsHorizontal;
    return CGSizeMake(itemWidth, 30);
}
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}

-(CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return 0;
}

-(CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
    return 0;
}

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    OSButtonBarItem* button = _buttons[indexPath.row];

    OSButtonBarCell* cell = [collectionView dequeueReusableCellWithReuseIdentifier:REUSUE_OS_TAB_CELL forIndexPath:indexPath];
   // cell.translatesAutoresizingMaskIntoConstraints = NO;
    cell.contentView.translatesAutoresizingMaskIntoConstraints = NO;
    cell.indexPath = indexPath;
    cell.titleLabel.text = button.text;
    cell.backgroundColor = button.backgroundColour;
    return cell;
}

-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return _buttons.count;
}

如果有人对可能发生的事情有任何建议，我将非常感激！

非常感谢克里斯