我设法让我的实现使用标准工作UICollectionViewFlowLayout
。我必须手动创建动画。
首先,我使用基本动画使已删除的单元格淡出:
- (void)tappedCloseButtonOnCell:(ScreenCell *)cell {
// We don't want to close our last screen.
if ([self screenCount] == 1u) {
return;
}
[UIView animateWithDuration:UINavigationControllerHideShowBarDuration
animations:^{
// Fade out the cell.
cell.alpha = 0.0f;
}
completion:^(BOOL finished) {
NSIndexPath *indexPath = [self.collectionView indexPathForCell:cell];
UIViewController *screen = [self viewControllerAtIndex:indexPath.item];
[self removeScreen:screen animated:YES];
}];
}
接下来,我使集合视图滚动到上一个单元格。滚动到所需的单元格后,我将删除已删除的单元格。
- (void)removeScreen:(UIViewController *)screen animated:(BOOL)animated {
NSParameterAssert(screen);
NSInteger index = [[self.viewControllerDictionaries valueForKeyPath:kViewControllerKey] indexOfObject:screen];
if (index == NSNotFound) {
return;
}
[screen willMoveToParentViewController:nil];
if (animated) {
dispatch_time_t popTime = DISPATCH_TIME_NOW;
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:index
inSection:0];
// Disables user interaction to make sure the user can't interact with
// the collection view during the time between when the scroll animation
// ends and the deleted cell is removed.
[self.collectionView setUserInteractionEnabled:NO];
// Scrolls to the previous item, if one exists. If we are at the first
// item, we just let the next screen slide in from the right.
if (index > 0) {
popTime = dispatch_time(DISPATCH_TIME_NOW, 0.5 * NSEC_PER_SEC);
NSIndexPath *targetIndexPath = [NSIndexPath indexPathForItem:index - 1
inSection:0];
[self.collectionView scrollToItemAtIndexPath:targetIndexPath
atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally
animated:YES];
}
// Uses dispatch_after since -scrollToItemAtIndexPath:atScrollPosition:animated:
// doesn't have a completion block.
dispatch_after(popTime, dispatch_get_main_queue(), ^{
[self.collectionView performBatchUpdates:^{
[self.viewControllerDictionaries removeObjectAtIndex:index];
[self.collectionView deleteItemsAtIndexPaths:@[indexPath]];
[screen removeFromParentViewController];
[self.collectionView setUserInteractionEnabled:YES];
} completion:NULL];
});
} else {
[self.viewControllerDictionaries removeObjectAtIndex:index];
[self.collectionView reloadData];
[screen removeFromParentViewController];
}
self.addPageButton.enabled = YES;
[self postScreenChangeNotification];
}
唯一有点可疑的部分是dispatch_after()
. 不幸-scrollToItemAtIndexPath:atScrollPosition:animated:
的是,没有完成块,所以我不得不模拟它。为了避免时间问题,我禁用了用户交互。这可以防止用户在删除单元格之前与集合视图进行交互。
我必须注意的另一件事是,由于单元重复使用,我必须将单元的 alpha 重置回 1。
我希望这可以帮助您使用 Safari 风格的标签选择器。我知道您的实现与我的不同,我希望我的解决方案也适用于您。