Transition Animator two parts of de middle

TTPopAnimator.h

@import Foundation;

@interface TTPopAnimator : NSObject <UIViewControllerAnimatedTransitioning>

@end

TTPopAnimator.m

#import "TTPopAnimator.h"

#define kTransitionDuration .35

@implementation TTPopAnimator

#pragma mark - UIViewControllerAnimatedTransitioning

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

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext
{
	UIViewController* toController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
	UIViewController* fromController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
	UIView* container = [transitionContext containerView];
	
	//get rects that represent the top and bottom halves of the screen
	CGSize viewSize = fromController.view.bounds.size;
	CGRect topFrame = CGRectMake(0, 0, viewSize.width, viewSize.height/2);
	CGRect bottomFrame = CGRectMake(0, viewSize.height/2, viewSize.width, viewSize.height/2);
	
	//create snapshots
	UIView* snapshot = [toController.view snapshotViewAfterScreenUpdates:YES];
	UIView* snapshotTop = [snapshot resizableSnapshotViewFromRect:topFrame afterScreenUpdates:NO withCapInsets:UIEdgeInsetsZero];
	UIView* snapshotBottom = [snapshot resizableSnapshotViewFromRect:bottomFrame afterScreenUpdates:NO withCapInsets:UIEdgeInsetsZero];
	
	//start the frames with an offset
	CGRect offsetTopFrame = topFrame;
	CGRect offsetBottomFrame = bottomFrame;
	offsetTopFrame.origin.y -= topFrame.size.height;
	offsetBottomFrame.origin.y += bottomFrame.size.height;
	snapshotTop.frame = offsetTopFrame;
	snapshotBottom.frame = offsetBottomFrame;
	
	//add our snapshots on top
	[container addSubview:snapshotTop];
	[container addSubview:snapshotBottom];
	
	[UIView animateKeyframesWithDuration:kTransitionDuration delay:0 options:UIViewKeyframeAnimationOptionCalculationModeLinear animations:^{
		
		//animate the top first
		[UIView addKeyframeWithRelativeStartTime:0 relativeDuration:1 animations:^{
			snapshotTop.frame = topFrame;
		}];
		
		//animate the bottom second
		[UIView addKeyframeWithRelativeStartTime:0 relativeDuration:1 animations:^{
			snapshotBottom.frame = bottomFrame;
		}];
		
	} completion:^(BOOL finished) {
		
		//don't forget to clean up
		[snapshotTop removeFromSuperview];
		[snapshotBottom removeFromSuperview];
		[fromController.view removeFromSuperview];
		[container addSubview:toController.view];
		
		[transitionContext completeTransition:finished];
	}];
}

@end

TTPushAnimator.h

@import Foundation;

@interface TTPushAnimator : NSObject <UIViewControllerAnimatedTransitioning>

@end

TTPushAnimator.m

#import "TTPushAnimator.h"

#define kTransitionDuration .35

@implementation TTPushAnimator

#pragma mark - UIViewControllerAnimatedTransitioning

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

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext
{
	UIViewController* toController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
	UIViewController* fromController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
	UIView* container = [transitionContext containerView];
	
	//get rects that represent the top and bottom halves of the screen
	CGSize viewSize = fromController.view.bounds.size;
	CGRect topFrame = CGRectMake(0, 0, viewSize.width, viewSize.height/2);
	CGRect bottomFrame = CGRectMake(0, viewSize.height/2, viewSize.width, viewSize.height/2);
	
	//create snapshots
	UIView* snapshotTop = [fromController.view resizableSnapshotViewFromRect:topFrame afterScreenUpdates:NO withCapInsets:UIEdgeInsetsZero];
	UIView* snapshotBottom = [fromController.view resizableSnapshotViewFromRect:bottomFrame afterScreenUpdates:NO withCapInsets:UIEdgeInsetsZero];
	snapshotTop.frame = topFrame;
	snapshotBottom.frame = bottomFrame;
	
	//remove the original view from the container
	[fromController.view removeFromSuperview];
	
	//add our destination view
	[container addSubview:toController.view];
	
	//add our snapshots on top
	[container addSubview:snapshotTop];
	[container addSubview:snapshotBottom];
	
	[UIView animateKeyframesWithDuration:kTransitionDuration delay:0 options:UIViewKeyframeAnimationOptionCalculationModeLinear animations:^{
		
		//adjust the new frames
		CGRect newTopFrame = topFrame;
		CGRect newBottomFrame = bottomFrame;
		newTopFrame.origin.y -= topFrame.size.height;
		newBottomFrame.origin.y += bottomFrame.size.height;
		
		//animate the top first
		[UIView addKeyframeWithRelativeStartTime:0 relativeDuration:1 animations:^{
			snapshotTop.frame = newTopFrame;
		}];
		
		//animate the bottom second
		[UIView addKeyframeWithRelativeStartTime:0 relativeDuration:1 animations:^{
			snapshotBottom.frame = newBottomFrame;
		}];
		
	} completion:^(BOOL finished) {
		
		//don't forget to clean up
		[snapshotTop removeFromSuperview];
		[snapshotBottom removeFromSuperview];
		
		[transitionContext completeTransition:finished];
		
	}];
}

@end

Usage

@interface : UIViewController <UINavigationControllerDelegate>

#pragma mark - UINavigationControllerDelegate

- (id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                   animationControllerForOperation:(UINavigationControllerOperation)operation
                                                fromViewController:(UIViewController *)fromVC
                                                  toViewController:(UIViewController *)toVC
{
    switch(operation)
    {
        case UINavigationControllerOperationPush:
            return [[TTPushAnimator alloc] init];
        case UINavigationControllerOperationPop:
            return [[TTPopAnimator alloc] init];
        default:
            return nil;
    }
}