UICollectionView和Supplementary View（标题） [英] UICollectionView and Supplementary View (header)

问题描述

尝试在我的 UICollectionView 中添加一个补充视图作为标题。我有问题让它工作。

Trying to add a a Supplementary view into my UICollectionView as a header. I'm having issues getting it to work.

我使用自定义 UICollectionViewFlowLayout 返回 contentSize 总是至少比帧大1个像素（我使用的是 UIFreshControl ，只有在<$ c $时才有效c> UICollectionView 滚动，并设置 collectionView.contentSize 直接无效）和 invalidateLayout 在 sectionInsert 和 itemSize 更改：

I use a custom UICollectionViewFlowLayout to return a contentSize that is always at least 1 pixel larger then the frame (I am using a UIFreshControl which will only work if the UICollectionView scrolls, and setting collectionView.contentSize directly does nothing) and to invalidateLayout on sectionInsert and itemSize changes:

-(void)setSectionInset:(UIEdgeInsets)sectionInset {
    if (UIEdgeInsetsEqualToEdgeInsets(super.sectionInset, sectionInset)) {
        return;
    }

    super.sectionInset = sectionInset;

    [self invalidateLayout];

}

-(void) setItemSize:(CGSize)itemSize {
    if (CGSizeEqualToSize(super.itemSize, itemSize)) {
        return;
    }

    super.itemSize = itemSize;

    [self invalidateLayout];
}

- (CGSize)collectionViewContentSize
{
    CGFloat height = [super collectionViewContentSize].height;

    // Always returns a contentSize larger then frame so it can scroll and UIRefreshControl will work
    if (height < self.collectionView.bounds.size.height) {
        height = self.collectionView.bounds.size.height + 1;
    }

    return CGSizeMake([super collectionViewContentSize].width, height);
}

我创建了一个 UICollectionReusableView 类只是一个 UIView ，带有 UILabel ：

I created a UICollectionReusableView class which is just a UIView with a UILabel:

@implementation CollectionHeaderView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        NSArray *arrayOfViews = [[NSBundle mainBundle] loadNibNamed:@"CollectionHeaderView" owner:self options:nil];

        if ([arrayOfViews count] < 1) {
            return nil;
        }

        if (![[arrayOfViews objectAtIndex:0] isKindOfClass:[UICollectionViewCell class]]) {
            return nil;
        }

        self = [arrayOfViews objectAtIndex:0];

        self.headerLabel.text = @"This is a header. There are many like it.";
        self.backgroundColor = [UIColor yellowColor];


    }
    return self;
}

尝试实施它：

DatasetLayout *collectionViewFlowLayout = [[DatasetLayout alloc] init];
collectionViewFlowLayout.itemSize = CGSizeMake(360, 160);
collectionViewFlowLayout.scrollDirection = UICollectionViewScrollDirectionVertical;
collectionViewFlowLayout.sectionInset = UIEdgeInsetsMake(16, 16, 16, 16);
collectionViewFlowLayout.minimumInteritemSpacing = 16;
collectionViewFlowLayout.minimumLineSpacing = 16;
collectionViewFlowLayout.headerReferenceSize = CGSizeMake(0, 100);

UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:collectionViewFlowLayout];
collectionView.translatesAutoresizingMaskIntoConstraints = FALSE;
collectionView.backgroundColor = [UIColor yellowColor];
collectionView.delegate = self;
collectionView.dataSource = self;

我注册课程：

[self.collectionView registerClass:[CollectionHeaderView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"CollectionHeaderView"];

并实施代表：

-(UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {

    CollectionHeaderView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"CollectionHeaderView" forIndexPath:indexPath];

    headerView.headerLabel.text = @"Blarg!";

    return headerView;
}

该行

collectionViewFlowLayout.headerReferenceSize = CGSizeMake(0, 100);

导致错误：

*** Assertion failure in -[UICollectionView _createPreparedSupplementaryViewForElementOfKind:atIndexPath:withLayoutAttributes:], /SourceCache/UIKit_Sim/UIKit-2380.17/UICollectionView.m:1150
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UICollectionView dataSource is not set'

如果我发表评论，它但没有标题。

If I comment it out, it runs but no header.

我做错了什么或者没有实现？

What am I doing wrong or not implementing?

推荐答案

我遇到了类似的问题，但是在我以编程方式弹出我的UICollectionViewController后，我的应用程序崩溃了。在某些原因（我认为它只是SDK中的一个错误）self.collectionView在其'控制器销毁后仍然存在，从而导致此失败：

I faced with the similar problem, but my app crashed after I programmatically pop my UICollectionViewController. In some reason (I think it's just a bug in SDK) self.collectionView was alive after its' controller destroy, thus causing this failure:

*** Assertion failure in -[UICollectionView _createPreparedSupplementaryViewForElementOfKind:atIndexPath:withLayoutAttributes:applyAttributes:], /SourceCache/UIKit/UIKit-2935.137/UICollectionView.m:1305
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UICollectionView dataSource is not set'

解决方案是在UICollectionViewController中覆盖-dealloc并手动释放self.collectionView。 ARC代码：

The solution is just override -dealloc in UICollectionViewController and release self.collectionView manually. ARC code:

- (void)dealloc {

    self.collectionView = nil;
}

希望这会为某人节省时间。

Hope this will save time for somebody.

这篇关于UICollectionView和Supplementary View（标题）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！