Unified, easy API for custom iOS view controller transitioning.

Perhaps you watched the 2013 WWDC talk or read the slightly spread-out documentation on how to use custom transitions between child view controllers, modal view controllers and in a navigation controller. Couple of minutes in, you're wandering in Protocolandia and you're lost. We don't blame you.

Installation

pod 'STPTransitions' (via CocoaPods)

Features (TL;DR)

• Child view controller transitions
• Modal view controller transitions (+ fix for landscape)
• Navigation controller transitions
• Unified, simple API

In the works:

• Full interactive transition support

Usage

First import the library's header:

#import <STPTransitions.h>

Quick start: STPBlockTransition

With STPBlockTransition, you can quickly create in-line transitions

STPTransition *snazzyTransition = [STPTransition transitionWithAnimation:
 ^(UIView *fromView,
   UIView *toView, 
   UIView *containerView, 
   void (^executeOnCompletion)(BOOL finished)) {
     // Your fabulous animations go here
}];

Note: You have two important responsibilities:

• fromView is a subview of containerView, toView is not. Add it when appropriate.
• Execute executeOnCompletion when the animation is completed (at the end of its completion block).

Using transition: navigation controller

To set up, assign the STPTransitionCenter singleton as navigation controller's delegate:

navigationController.delegate = [STPTransitionCenter sharedInstance];

Now simply push and pop view controllers using:

[self.navigationController pushViewController:viewController
                              usingTransition:snazzyTransition];
// and                              
[self.navigationController popViewControllerUsingTransition:transition];

Using transition: child controllers

No setup is needed. In the parent controller, switch between two child controllers using:

[self transitionFromViewController:oldChildViewController
                  toViewController:newChildViewController
                   usingTransition:snazzyTransition];

Note: This transition currently cannot be interactive. If you'd like this feature, voice your opinion in the Issues.

Using transition: modal controller

To set up, assign the STPTransitionCenter singleton as presenting controller's delegate:

self.transitioningDelegate = [STPTransitionCenter sharedInstance];

Now simply present and dismiss view controllers using:

[self presentViewController:viewController
            usingTransition:snazzyTransition
                 completion:completion];
// and                
[self dismissViewControllerUsingTransition:snazzyTransition
                                completion:(void (^)(void))completion];

Proper usage: Subclassing STPTransition

To maintain thin view controllers and a nicely separated codebase, you probably don't want to keep your transition animation code in the view controller itself. It also allows for the transition to be reused. You achieve both of these goals by subclassing STPTransition.

See the example project for a hands-on code example.

Reverse transitions

When pushing or presenting a view controller, you can specify which transition should happen when the returning (i.e. pop or dismiss) operation takes place. To do that, simply assign the transition object to be used to reverseTransition.

This greatly helps decoupling, because the pushed/presented controller doesn't have to know anything about how it's being shown.

Pro tip: Just assign reverseTransition to be a new instance of the same class you just created for the push/present. See below on how to easily handle both animations in one class.

Modal transitions in landscape orientation

As of iOS 7.0.2, custom modal transitions in landscape orientation are not very usable, because the views iOS gives you have all kinds of messed up frames and transforms. STPTransitions attempts to solve this for you, providing you a view in the orientation you'd expect. This has been tested and works for iPad full-screen landscape custom modals.

Regular and reverse implementation in one class

Often, you don't want to have two STPTransition subclasses for the same type of animation, i.e. one for going forward, and one for going back. When going back – popping or dismissing a controller – the transition instance automatically gets assigned YES for isReversed.

Pro tip: Reuse code and handle both forward and backward transitions in the same class. Usually it means having if/else conditionals on isReversed.

Triggering by a gesture recognizer

A transition can have a gesture recognizer assigned. The transition gets automatically kicked off when the recognizer's gesture is detected.

Note: This does not mean the transition is interactive (e.g. follows users finger), although it can be.

Interactive transitions

TODO: Interactive transitions aren't fully supported yet.

1. Set the interactive property to YES.
2. Assign gestureRecognizer that is going to track the progress.
3. Implement interactiveGesturePercentageCompletionForPoint: in your subclass.

Note: An interactive transition doesn't necessarily need to be triggered interactively, e.g. it can be triggered by a button and happen non-interactively. The wasTriggeredInteractively property informs about the way it was triggered.

Included transitions

If you'd like the library to include some configurable, often used transitions by default, voice your opinion in the Issues. Contributions are also welcome.

FAQ

Q: I need for my UINavigationController to have my own delegate. What do I do?
A: Subclass your delegate from STPTransitionCenter and use your own instance instead of the default center. You're responsible for keeping that object around, as you're not using the singleton. Make sure you call super in any delegate methods that are implemented by the center.

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Created by Stepan Hruda. If you follow him on Twitter, he's gonna have a good time.

Thanks goes to Josh Vickery and ShopKeep POS for contributions and feedback.

Released under MIT License.