ios - 如何在 Objective-C 中将带有补充 View 的标题添加到 UiCollectionView？

Question

我有一个包含 CollectionView 的 ViewController :

- (void)viewDidLoad
{
    UICollectionViewFlowLayout *layout = [UICollectionViewFlowLayout new];
    collectionview = [[UICollectionView alloc]initWithFrame:CGRectZero collectionViewLayout:layout];
    collectionview.backgroundColor = [UIColor colorWithRed:0.86 green:0.86 blue:0.86 alpha:1.0];
    collectionview.translatesAutoresizingMaskIntoConstraints = false;
    collectionview.delegate = self;
    collectionview.dataSource = self;
    collectionview.bounces = true;
    [collectionview registerClass:[CollectionViewCell1 class] forCellWithReuseIdentifier:@"cell1"];
    [self.view addSubview:collectionview];
    [collectionview sdc_alignEdgesWithSuperview:UIRectEdgeAll];
    [collectionview registerClass:[RecipeCollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView"];
}

-(UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    UICollectionReusableView *reusableview = nil;
    RecipeCollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView" forIndexPath:indexPath];
    headerView.backgroundColor = [UIColor greenColor];
    headerView.title.text = @"ABC";
    reusableview = headerView;

    return reusableview;
}

和 RecipeCollectionReusableView 是:

- (void)initialize
{
    _title = [UILabel new];
    _title.translatesAutoresizingMaskIntoConstraints = false;
    [self addSubview:_title];
    [_title sdc_centerInSuperview];
}

但运行后屏幕上没有任何标题。

Answer 1

您是否为 header 执行了所需的实现？

https://developer.apple.com/documentation/uikit/uicollectionviewdelegateflowlayout/1617702-collectionview?language=objc

collectionView:layout:referenceSizeForHeaderInSection:

Return Value The size of the header. If you return a value of size (0, 0), no header is added.

Discussion If you do not implement this method, the flow layout uses the value in its headerReferenceSize property to set the size of the header. During layout, only the size that corresponds to the appropriate scrolling direction is used. For example, for the vertical scrolling direction, the layout object uses the height value returned by your method. (In that instance, the width of the header would be set to the width of the collection view.) If the size in the appropriate scrolling dimension is 0, no header is added.