ViewControllerTransitionsPart1-5

TTPushAnimator.m

- (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 animateWithDuration:kTransitionDuration animations:^{
		
		//adjust the new frames
		CGRect newTopFrame = topFrame;
		CGRect newBottomFrame = bottomFrame;
		newTopFrame.origin.y -= topFrame.size.height;
		newBottomFrame.origin.y += bottomFrame.size.height;
		
		//set the frames to animate them
		snapshotTop.frame = newTopFrame;
		snapshotBottom.frame = newBottomFrame;
		
	} completion:^(BOOL finished){
		
		//don't forget to clean up
		[snapshotTop removeFromSuperview];
		[snapshotBottom removeFromSuperview];
		
		[transitionContext completeTransition:finished];
	}];
}