A slide-and-zoom animation using collections views

PASHideDetailAnimator.m

#import <Foundation/Foundation.h>

#import "PASConstants.h"
#import "PASViewController.h"

@interface PASHideDetailAnimator : NSObject <UIViewControllerAnimatedTransitioning>

@end

@implementation PASHideDetailAnimator

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UICollectionView *fromCollectionView = [(UICollectionViewController *)fromViewController collectionView];
    UICollectionView *toCollectionView = [(UICollectionViewController *)toViewController collectionView];
    
    UIView *containerView = [transitionContext containerView];
    [containerView addSubview:toViewController.view];
    [fromViewController.view setAlpha:0.0f];
    
    CGRect originRect = [self originRectFromContext:transitionContext];
    CGRect destinationRect = [self destinationRectFromContext:transitionContext];
    destinationRect = [containerView convertRect:destinationRect fromView:toCollectionView];
    
    CGRect firstRect = CGRectMake(originRect.origin.x, originRect.origin.y, originRect.size.width, destinationRect.size.height);
    CGRect secondRect = destinationRect;
    
    UIEdgeInsets insets = UIEdgeInsetsMake(68.0f, 0.0f, 5.0f, 0.0f);
    CGRect snapshotRect = CGRectMake(originRect.origin.x, originRect.origin.y, originRect.size.width, destinationRect.size.height);
    
    UIView *snapshot = [fromCollectionView resizableSnapshotViewFromRect:snapshotRect afterScreenUpdates:NO withCapInsets:insets];
    [snapshot setFrame:[containerView convertRect:originRect fromView:fromCollectionView]];
    [containerView addSubview:snapshot];
    
    [UIView animateKeyframesWithDuration:PASPassAnimationDuration delay:0.0f options:0 animations:^{
        [UIView addKeyframeWithRelativeStartTime:0.0f relativeDuration:0.33f animations:^{
            [snapshot setFrame:[containerView convertRect:firstRect fromView:fromCollectionView]];
        }];
        
        [UIView addKeyframeWithRelativeStartTime:0.33f relativeDuration:0.33f animations:^{
            [snapshot setFrame:secondRect];
        }];
        
        [UIView addKeyframeWithRelativeStartTime:0.66f relativeDuration:0.33f animations:^{
            [toViewController.view setAlpha:1.0f];
        }];
    } completion:^(BOOL finished) {
        [transitionContext completeTransition:finished];
        [fromViewController.view removeFromSuperview];
        [snapshot removeFromSuperview];
    }];
}

- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext {
    return PASPassAnimationDuration;
}

- (CGRect)originRectFromContext:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    if ([fromViewController isKindOfClass:[UICollectionViewController class]]) {
        UICollectionView *collectionView = [(UICollectionViewController *)fromViewController collectionView];
        NSIndexPath *indexPath = [[collectionView indexPathsForVisibleItems] firstObject];
        UICollectionViewLayoutAttributes *attributes = [collectionView layoutAttributesForItemAtIndexPath:indexPath];
        return CGRectInset(attributes.frame, 15.0f, 0.0f);
    }
    return CGRectZero;
}

- (CGRect)destinationRectFromContext:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    if ([toViewController isKindOfClass:[PASViewController class]]) {
        UICollectionView *collectionView = [(PASViewController *)toViewController collectionView];
//        NSIndexPath *indexPath = [(PASViewController *)toViewController animationIndexPath];
        NSIndexPath *indexPath = [self originIndexPathFromContext:transitionContext];
        UICollectionViewLayoutAttributes *attributes = [collectionView layoutAttributesForItemAtIndexPath:indexPath];
        return attributes.frame;
    }
    return CGRectZero;
}

- (NSIndexPath *)originIndexPathFromContext:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    if ([fromViewController isKindOfClass:[UICollectionViewController class]]) {
        UICollectionView *collectionView = [(UICollectionViewController *)fromViewController collectionView];
        NSIndexPath *indexPath = [[collectionView indexPathsForVisibleItems] firstObject];
        return indexPath;
    }
    return nil;
}

@end

PASShowDetailAnimator.m

#import <Foundation/Foundation.h>
#import "PASConstants.h"

@interface PASShowDetailAnimator : NSObject <UIViewControllerAnimatedTransitioning>

@end

@implementation PASShowDetailAnimator

- (id)init {
    if ((self = [super init])) {
        //
    }
    return self;
}

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    
    UICollectionView *fromCollectionView = [(UICollectionViewController *)fromViewController collectionView];
//    UICollectionView *toCollectionView = [(UICollectionViewController *)toViewController collectionView];
    
    UIView *containerView = [transitionContext containerView];
    [containerView setBackgroundColor:[UIColor darkGrayColor]];
    
    [toViewController.view setAlpha:0.0f];
    [containerView addSubview:toViewController.view];
    
    CGRect originRect = [self originRectFromContext:transitionContext];
    CGRect destinationRect = CGRectMake(15.0f, 105.0f, 290.0f, 422.0f);
    
    CGRect firstRect = CGRectMake(destinationRect.origin.x, destinationRect.origin.y, destinationRect.size.width, originRect.size.height);
    CGRect secondRect = CGRectMake(destinationRect.origin.x, destinationRect.origin.y, destinationRect.size.width, destinationRect.size.height);
    
    UIEdgeInsets insets = UIEdgeInsetsMake(80.0f, 0.0f, 5.0f, 0.0f);
    UIView *snapshot = [fromCollectionView resizableSnapshotViewFromRect:originRect afterScreenUpdates:NO withCapInsets:insets];
    [snapshot setFrame:[containerView convertRect:originRect fromView:fromCollectionView]];
    [containerView addSubview:snapshot];
    
    [UIView animateKeyframesWithDuration:PASPassAnimationDuration delay:0.0f options:0 animations:^{
        [UIView addKeyframeWithRelativeStartTime:0.0f relativeDuration:0.33f animations:^{
            [fromViewController.view setAlpha:0.0f];
        }];
        
        [UIView addKeyframeWithRelativeStartTime:0.33f relativeDuration:0.33f animations:^{
            [snapshot setFrame:firstRect];
        }];
        
        [UIView addKeyframeWithRelativeStartTime:0.66f relativeDuration:0.33f animations:^{
            [snapshot setFrame:secondRect];
        }];
    } completion:^(BOOL finished) {
        [transitionContext completeTransition:finished];
        
        [toViewController.view setAlpha:1.0f];
        [fromViewController.view removeFromSuperview];
        [containerView addSubview:toViewController.view];
        [snapshot removeFromSuperview];
    }];
}

- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext {
    return PASPassAnimationDuration;
}

- (CGRect)originRectFromContext:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    if ([fromViewController isKindOfClass:[UICollectionViewController class]]) {
        UICollectionView *collectionView = [(UICollectionViewController *)fromViewController collectionView];
        NSIndexPath *indexPath = [[collectionView indexPathsForSelectedItems] firstObject];
        UICollectionViewLayoutAttributes *attributes = [collectionView layoutAttributesForItemAtIndexPath:indexPath];
        return attributes.frame;
    }
    return CGRectZero;
}

- (CGRect)destinationRectFromContext:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    if ([toViewController isKindOfClass:[UICollectionViewController class]]) {
        UICollectionView *collectionView = [(UICollectionViewController *)toViewController collectionView];
        NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
        
        UICollectionViewLayoutAttributes *attributes = [collectionView layoutAttributesForItemAtIndexPath:indexPath];
        return attributes.frame;
    }
    return CGRectZero;
}

- (NSArray *)snapshotFramesFromContext:(id<UIViewControllerContextTransitioning>)transitionContext {
    __block NSMutableArray *frames = [NSMutableArray array];
    UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    if ([fromViewController isKindOfClass:[UICollectionViewController class]]) {
        UICollectionView *collectionView = [(UICollectionViewController *)fromViewController collectionView];
        NSMutableSet *mutableSet = [NSMutableSet setWithArray:[collectionView indexPathsForVisibleItems]];
        [mutableSet minusSet:[NSSet setWithArray:[collectionView indexPathsForSelectedItems]]];
        [[mutableSet allObjects] enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
            NSIndexPath *indexPath = (NSIndexPath *)obj;
            UICollectionViewLayoutAttributes *attributes = [collectionView layoutAttributesForItemAtIndexPath:indexPath];
            [frames addObject:[NSValue valueWithCGRect:attributes.frame]];
        }];
    }
    return [NSArray arrayWithArray:frames];
}

@end