我正在尝试使用UICollectionView创建一堆照片，用户可以将照片滑到一边。当拖动照片时，它会变小（达到最小比例）并且后面的照片会放大到最大比例。此最大比例是前景照片的原始大小。
当拖动前景照片的平移手势结束时，如果是最小刻度，则将其发送到堆栈的背面，否则，将其动画回屏幕中心并放大回原始大小（以及背后不断增长的照片）。
我希望你还和我在一起哈哈。
现在，假设被拖动的照片处于最小尺寸，我删除了UICollectionView的用户互动，再次将照片动画显示到屏幕中心，并将其大小设置为动画以匹配其余部分背景图片。然后我将单元格发送到UICollectionView子视图的后面。
一旦完成所有这些动画，我会通过在前面添加照片来更新我的数据源（图像数组），然后在前面删除该照片。
然后，我更新UICollectionView。这包括批量更新，其中我在NSIndexPath 0：0删除项目，然后在NSIndexPath插入项目（[照片计数] - 1）：0。
当此批量更新完成后，我重新加载UICollectionView（因为只有NSIndexPath 0：0处的项目具有平移手势）并重新添加用户交互到UICollectionView。
我希望这是有道理的。
备注
背景照片的大小是80％的百分比。
前景照片的大小是100％的百分比。
这是相对于适合iPhone屏幕的UICollectionView。
我的问题
我的代码似乎运行得很好。我的问题来自于当我将手指从屏幕上移开（平移手势结束）和照片的动画（将其居中到屏幕中心并像其他背景照片一样调整大小）结束。
拖出的照片重新出现在屏幕上，尺寸从背景照片的尺寸（80％）到前景照片的尺寸（100％）然后逐渐消失。一旦发生这种情况，照片将按预期重新排序。
有谁知道为什么会这样？
这是我的Pan Gesture代码：
CGPoint touchTranslation = [gesture translationInView:self.view];
static CGPoint originalCenter;
DIGalleryCollectionViewLayout *galleryCollectionViewLayout = (DIGalleryCollectionViewLayout *)self.galleryCollectionView.collectionViewLayout;
if (gesture.state == UIGestureRecognizerStateBegan) {
//
// Began.
//
originalCenter = gesture.view.center;
} else if (gesture.state == UIGestureRecognizerStateChanged) {
//
// Changed.
//
CGPoint translate = [gesture translationInView:gesture.view.superview];
touchTranslation = CGPointMake(originalCenter.x + translate.x, originalCenter.y + translate.y);
[gesture.view setCenter:touchTranslation];
CGPoint pointsPhotoIsMovedBy = CGPointMake(fabsf(fabsf(originalCenter.x) - fabsf(touchTranslation.x)),
fabsf(fabsf(originalCenter.y) - fabsf(touchTranslation.y)));
// Update cells.
//
CGFloat currentIncrement = MAX(pointsPhotoIsMovedBy.x, pointsPhotoIsMovedBy.y);
for (NSIndexPath *indexPath in self.galleryCollectionView.indexPathsForVisibleItems) {
UICollectionViewCell *cell = [self.galleryCollectionView cellForItemAtIndexPath:indexPath];
if ([indexPath isEqual:[NSIndexPath indexPathForItem:0 inSection:0]]) {
//
// Front.
//
CGFloat frontScalePercent = MIN(GalleryCollectionViewLayoutFrontRatioDefault,
MAX(GalleryViewFrontScaleMinimum, GalleryCollectionViewLayoutFrontRatioDefault - (currentIncrement / 250.0f)));
[cell setTransform:CGAffineTransformMakeScale(frontScalePercent, frontScalePercent)];
} else if ([indexPath isEqual:[NSIndexPath indexPathForItem:1 inSection:0]]) {
//
// Next.
//
CGFloat nextScalePercent = MAX(GalleryCollectionViewLayoutBackRatioDefault,
MIN(GalleryViewNextScaleMaximum, (currentIncrement / 150.0f)));
[cell setTransform:CGAffineTransformMakeScale(nextScalePercent, nextScalePercent)];
} else {
//
// Background.
//
[cell setTransform:CGAffineTransformMakeScale(GalleryCollectionViewLayoutBackRatioDefault,
GalleryCollectionViewLayoutBackRatioDefault)];
}
}
} else if (gesture.state == UIGestureRecognizerStateEnded) {
//
// Ended.
//
if (gesture.view.transform.a == GalleryViewFrontScaleMinimum) {
//
// Next photo.
//
[self.galleryCollectionView setUserInteractionEnabled:NO];
[self.galleryCollectionView sendSubviewToBack:gesture.view];
[UIView animateWithDuration:0.3f
animations:^{
[gesture.view setCenter:self.galleryCollectionView.center];
[gesture.view setTransform:CGAffineTransformMakeScale(GalleryCollectionViewLayoutBackRatioDefault,
GalleryCollectionViewLayoutBackRatioDefault)];
}
completion:^(BOOL finished) {
//
// Data source
//
NSMutableArray *photos = [self.photos mutableCopy];
[photos addObject:[photos objectAtIndex:0]];
[photos removeObjectAtIndex:0];
[self setPhotos:photos];
// Contents
//
[self.galleryCollectionView performBatchUpdates:^{
[self.galleryCollectionView deleteItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:0 inSection:0]]];
[self.galleryCollectionView insertItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:(self.photos.count - 1) inSection:0]]];
} completion:^(BOOL finished) {
[self.galleryCollectionView reloadData];
[self.galleryCollectionView setUserInteractionEnabled:YES];
}];
}];
} else {
//
// Stay.
//
[UIView animateWithDuration:0.3f
delay:0.0f
options:UIViewAnimationOptionCurveEaseIn
animations:^{
//
// Front cell.
//
[gesture.view setCenter:self.galleryCollectionView.center];
[gesture.view setTransform:CGAffineTransformMakeScale(GalleryCollectionViewLayoutFrontRatioDefault,
GalleryCollectionViewLayoutFrontRatioDefault)];
// Next cell.
//
for (NSIndexPath *indexPath in self.galleryCollectionView.indexPathsForVisibleItems) {
if ([indexPath isEqual:[NSIndexPath indexPathForItem:1 inSection:0]]) {
//
// Next.
//
UICollectionViewCell *cell = [self.galleryCollectionView cellForItemAtIndexPath:indexPath];
[cell setTransform:CGAffineTransformMakeScale(GalleryCollectionViewLayoutBackRatioDefault,
GalleryCollectionViewLayoutBackRatioDefault)];
}
}
}
completion:^(BOOL finished) {
[galleryCollectionViewLayout setFrontRatio:GalleryCollectionViewLayoutFrontRatioDefault];
[galleryCollectionViewLayout setNextRatio:GalleryCollectionViewLayoutBackRatioDefault];
[galleryCollectionViewLayout invalidateLayout];
}];
}
}
这是我的prepareLayout：集合视图布局的代码：
NSMutableDictionary *newLayoutInfo = [NSMutableDictionary dictionary];
NSMutableDictionary *cellLayoutInfo = [NSMutableDictionary dictionary];
NSIndexPath *indexPath;
for (NSInteger section = 0; section < [self.collectionView numberOfSections]; section++) {
NSInteger itemCount = [self.collectionView numberOfItemsInSection:section];
for (NSInteger item = 0; item < itemCount; item++) {
indexPath = [NSIndexPath indexPathForItem:item inSection:section];
UICollectionViewLayoutAttributes *itemAttributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
[itemAttributes setSize:[self sizeForPhotoAtIndexPath:indexPath inContainerOfSize:self.collectionView.bounds.size]];
[itemAttributes setCenter:self.collectionView.center];
// Z Index.
//
NSInteger zIndex = itemCount - item;
[itemAttributes setZIndex:zIndex];
// Scale cells based on z position.
//
if (zIndex == itemCount) {
//
// Foreground.
//
[itemAttributes setTransform:CGAffineTransformMakeScale(self.frontRatio, self.frontRatio)];
} else if (zIndex == itemCount - 1) {
//
// Next.
//
[itemAttributes setTransform:CGAffineTransformMakeScale(self.nextRatio, self.nextRatio)];
} else {
//
// Background.
//
[itemAttributes setTransform:CGAffineTransformMakeScale(GalleryCollectionViewLayoutBackRatioDefault,
GalleryCollectionViewLayoutBackRatioDefault)];
}
cellLayoutInfo[indexPath] = itemAttributes;
}
}
newLayoutInfo[GalleryCollectionViewLayoutCellKind] = cellLayoutInfo;
self.layoutInfo = newLayoutInfo;
作为附加参考，这是我的sizeForPhotoAtIndexPath代码：inContainerOfSize：
UIImage *photo = [[(DIGalleryViewController *)self.collectionView.delegate photos] objectAtIndex:indexPath.row];
CGSize size = CGSizeMake(photo.size.width, photo.size.height);
UIGraphicsBeginImageContext(containerSize);
[photo drawInRect:CGRectMake(0.0f, 0.0f, containerSize.width, containerSize.height)];
UIImage *resizedPhoto = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CGFloat ratio = photo.size.width / resizedPhoto.size.width;
size = CGSizeMake(resizedPhoto.size.width, photo.size.height / ratio);
return size;