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copied!<p>Here is a code that does custom animation both for back button and when you call <code>popRootViewController:</code> method.</p> <p>It's a class that extends <code>UINavigationViewController</code> which by itself contradicts Apple's docs also it assigns private variable using KVO, which might stop working as soon as engineers change <code>UINavigationController</code> class so use it a t your own risk.</p> <pre><code>#import "MyNavigationController.h" @interface MyNavigationController () <UINavigationBarDelegate> { // Flag that we will use to avoid collisions between navgiation bar // when we call popViewControllerAnimated: method directly BOOL _isPopping; } - (UIViewController *)myPopViewControllerAniamted:(BOOL)animated; @end @implementation MyNavigationController - (id)init { self = [super init]; if (!self) return nil; // We can't intercept delegation of the original navigation bar, // we have to replace it with our own, by assigning new instance to // the private _navigationBar vairable UINavigationBar *navigationBar = [[UINavigationBar alloc] init]; navigationBar.delegate = self; [self setValue:navigationBar forKey:@"_navigationBar"]; return self; } // This is the delegate method called when you're about to pop navigation item - (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item { // If we're in the process of popping items we don't want to reenter if (!_isPopping) { [self myPopViewControllerAniamted:YES]; } return YES; } // Similarly we have to override popToRootViewControllerAnimated: // The only difference would be that we use not previous view as a // target for the transfition, but the very first view - (UIViewController *)popViewControllerAnimated:(BOOL)animated { return [self myPopViewControllerAniamted:animated]; } // Our custom popping method - (UIViewController *)myPopViewControllerAniamted:(BOOL)animated { _isPopping = YES; // If we got here, we have at least two view controllers in the stack UIViewController *currentViewController = self.topViewController; if (animated && self.viewControllers.count > 1) { UIView *currentView = currentViewController.view; UIViewController *previousViewController = [self.viewControllers objectAtIndex:self.viewControllers.count - 2]; UIView *previousView = previousViewController.view; previousView.alpha = 0.0; [currentView.superview insertSubview:previousView belowSubview:currentView]; // I use UIView just for the sake of the simplicity of this example // In case of core animation you will have to deal with delegates // to trigger view controller popping when animation finishes [UIView animateWithDuration:0.33 delay:0.0 options:UIViewAnimationOptionCurveEaseInOut animations:^{ currentView.alpha = 0.0; previousView.alpha = 1.0; } completion:^(BOOL finished) { [super popViewControllerAnimated:NO]; _isPopping = NO; }]; } else { [super popViewControllerAnimated:NO]; _isPopping = NO; } return currentViewController; } @end </code></pre> <p>Once again, it was done purely as exercise of what is possible, I would highly recommend reading <a href="http://developer.apple.com/library/ios/#featuredarticles/ViewControllerPGforiPhoneOS/Introduction/Introduction.html" rel="nofollow">UIViewController guide</a>, probably <a href="http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIViewController_Class/Reference/Reference.html#//apple_ref/doc/uid/TP40006926-CH3-SW81" rel="nofollow">Container View Controller</a> can satisfy you needs as a designated way of customizing view controller behaviour.</p> <p>Hope it helps!</p>

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