Question

我目前正在为iOS项目开发图片库。该项目完全使用自动布局。

我有UICollectionView并使用全屏细胞。为了保持可见单元格，我在旋转之前存储indexPath并在布局子视图之后选择所需的单元格。

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
    NSUInteger itemIndex = [[self collectionView] contentOffset].x / CGRectGetWidth([[self collectionView] bounds]);
    [self setCurrentIndexPath:[NSIndexPath indexPathForItem:itemIndex inSection:0]];
}


- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    [[self collectionView] scrollToItemAtIndexPath:[self currentIndexPath]
                                  atScrollPosition:UICollectionViewScrollPositionCenteredVertically | UICollectionViewScrollPositionCenteredHorizontally
                                          animated:NO];
}

这一切都很有效且稳定。但是当选择第二个或下一个单元格并旋转时，第一个单元格会在新位置滑动时略微覆盖当前单元格。

我现在想要隐藏所有的屏幕外细胞。所以这就是我到目前为止所做的：

- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
    [cell setHidden:NO];
}

- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
    [cell setHidden:YES];
}

第二种方法是在集合视图上方有一个覆盖视图，然后在它前面有单元格图像视图：

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
    NSUInteger itemIndex = [[self collectionView] contentOffset].x / CGRectGetWidth([[self collectionView] bounds]);
    [self setCurrentIndexPath:[NSIndexPath indexPathForItem:itemIndex inSection:0]];

    JFWImageViewCollectionViewCell *cell = (JFWImageViewCollectionViewCell *)[[self collectionView] cellForItemAtIndexPath:[self currentIndexPath]];
    [[[cell imageView] layer] setZPosition:2];

    if (!_rotationCoverView) {
        [self setRotationCoverView:[UIView new]];
        [[self rotationCoverView] setBackgroundColor:[UIColor blackColor]];
        [[self rotationCoverView] setTranslatesAutoresizingMaskIntoConstraints:NO];

        [[self rotationCoverView] layer] setZPosition:1];

        [[self view] addSubview:[self rotationCoverView]];

        [[self view] addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[cover]|"
                                                                            options:0
                                                                            metrics:nil
                                                                              views:@{@"cover": [self rotationCoverView]}]];
        [[self view] addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[cover]|"
                                                                            options:0
                                                                            metrics:nil
                                                                              views:@{@"cover": [self rotationCoverView]}]];
    }
}

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    JFWImageViewCollectionViewCell *cell = (JFWImageViewCollectionViewCell *)[[self collectionView] cellForItemAtIndexPath:[self currentIndexPath]];
    [[[cell imageView] layer] setZPosition:0];

    [[self rotationCoverView] removeFromSuperview];
    [self setRotationCoverView:nil];
}

我尝试了zPosition以及-[UIView sendSubViewToFront:]及其兄弟姐妹的各种组合。

那么如何隐藏所有屏幕外单元格或逐层定位呢？

旋转期间全屏UICollectionViewCells重叠

0 个答案: