iOS UICollectionView 页眉和页脚位置

Question

在iOS 7中工作，如何指定头&页脚框进入UICollectionView？

我有一个自定义的UICollectionViewFlowLayout。我已覆盖

-(void)prepareLayout
-(NSArray*) layoutAttributesForElementsInRect:(CGRect)rect
-(UICollectionViewLayoutAttributes*) layoutAttributesForSupplementaryViewOfKind: (NSString*)kind atIndexPath:(NSIndexPath*)indexPath

我的问题是，我不知道如何指定标头位置。我已经指定prepareLayout:中存在标头

-(void)prepareLayout
{
[super prepareLayout];
boundsSize = self.collectionView.bounds.size;
midX = boundsSize.width / 2.0f;
curIndex = 0;
self.headerReferenceSize = CGSizeMake(CELL_SIZE, TITLE_HEIGHT);
self.footerReferenceSize = CGSizeMake(0, 0);
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
self.sectionInset = UIEdgeInsetsMake(TOP_INSET, LEFT_INSET, BOTTOM_INSET, RIGHT_INSET);
self.minimumLineSpacing = LINE_SPACING;
self.minimumInteritemSpacing = INTERIM_SPACING;
self.itemSize = CGSizeMake(CELL_SIZE, CELL_SIZE);
}

我只是不知道要设置的自定义FlowLayout的正确属性，因为似乎没有像"HeaderLocation"这样的东西要设置，无论是作为LayoutAttributes还是在布局对象本身中。现在，当我希望它们出现在每个图像上方时(水平滚动(，它会出现在我的图像旁边/图像之间。

我尝试过以下几种：

-(UICollectionReusableView*) collectionView: (UICollectionView*)collectionView viewForSupplementaryElementOfKind:(NSString*)kind atIndexPath:(NSIndexPath*)indexPath
{
    NSLog(@"**ViewForSupplementaryElementOfKind called***");
    CGFloat centerX = collectionView.center.x;
    CGFloat centerY = collectionView.center.y;
    CGFloat titleWidth = [MyLayout titleWidth];
    CGFloat titleHeight = [MyLayout titleHeight];
    MyTitleView* titleView = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:ImageTitleIdentifier forIndexPath:indexPath];
    titleView.frame = CGRectMake(centerX - titleWidth/2.0,
                                 0.0,
                                 titleWidth,
                                 titleHeight);
    return titleView;
}

这行不通。标题出现在上面，与一堆其他标题重叠，然后当我开始滚动(水平(时，它们跳回到错误的位置，在图像之间水平移动，而不是在上面。

PS>请不要建议任何与NIB或XIB放置有关的内容。我使用的是UICollectionView，而不是UICollectionViewController，所以我实际上没有典型的单元格可供使用。布局是完全通过程序完成的——仅从代码开始——所以我不能简单地打开XIB文件并调整文本框的位置。

Answer 1

修改-layoutAttributesForElementsInRect返回的属性是正确的方法，但如果您想更改屏幕外页眉和页脚的位置，您可能需要自己获取补充视图属性。

例如，在UICollectionViewFlowLayout子类中：

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSMutableArray *attributesArray = [[super layoutAttributesForElementsInRect:rect] mutableCopy];
    // the call to super only returns attributes for headers that are in the bounds,
    // so locate attributes for out of bounds headers and include them in the array
    NSMutableIndexSet *omittedSections = [NSMutableIndexSet indexSet];
    for (UICollectionViewLayoutAttributes *attributes in attributesArray) {
        if (attributes.representedElementCategory == UICollectionElementCategoryCell) {
            [omittedSections addIndex:attributes.indexPath.section];
        }
    }
    for (UICollectionViewLayoutAttributes *attributes in attributesArray) {
        if ([attributes.representedElementKind isEqualToString:UICollectionElementKindSectionHeader]) {
            [omittedSections removeIndex:attributes.indexPath.section];
        }
    }
    [omittedSections enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:idx];
        UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                                                                                            atIndexPath:indexPath];
        [attributesArray addObject:attributes];
    }];
    for (UICollectionViewLayoutAttributes *attributes in attributesArray) {
        if ([attributes.representedElementKind isEqualToString:UICollectionElementKindSectionHeader]) {
            // adjust any aspect of each header's attributes here, including frame or zIndex
        }
    }
    return attributesArray;
}

Answer 2

CollectionView标头高度设置在CollectionView委托之下

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section

并在代理下方的集合视图标题中设置视图

- (UICollectionReusableView*)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    UICollectionReusableView * view = nil;
    if ([kind isEqualToString:UICollectionElementKindSectionHeader])
    {
        ColorSectionHeaderView *header = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                                                                            withReuseIdentifier:NSStringFromClass([ColorSectionHeaderView class])
                                                                                   forIndexPath:indexPath];
        header.sectionIndex = indexPath.section;
        header.hideDelete = collectionView.numberOfSections == 1; // hide when only one section
        header.delegate = self;
        view = header;
    }
return view;

}

ViewDidLoad 中的Ragistred类

-(void)ViewDidLoad
{
[collectionView registerNib:[UINib nibWithNibName:NSStringFromClass([ColorSectionFooterView class]) bundle:nil]
     forSupplementaryViewOfKind:UICollectionElementKindSectionFooter
            withReuseIdentifier:NSStringFromClass([ColorSectionFooterView class])];
   [Super ViewDidLoad];
}