Model View Controller MVC - PowerPoint PPT Presentation

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Build and run your project and tap one of the herb images: Nothing happens. The difference between these two groups is that the interactive transitions are controlled by the user through a continuous gesture.

Some of these are implemented using only a UIViewControllerTransitioningDelegate, but if we really want to perform completely customizable ones, we need to go one step deeper and implement a. In custom view controllers, you can change the behavior of these methods to something more suitable for your view controller.

How To Make A UIViewController Transition Animation Like in the Ping App

In , took us through the new custom in iOS 7. Note that I am talking about custom container view controllers as direct subclasses of UIViewController, not UITabBarController or UINavigationController subclasses. There is no ready-to-use API for your custom container UIViewController subclass that allows an arbitrary animation controller to automatically conduct the transition from one of your child view controllers to another, interactively or non-interactively. Before We Begin You may ask yourself a question or two at this point, so let me answer them for you: Why not just subclass UINavigationController or UITabBarController and get the support for free? Maybe you want a very specific appearance or behavior, far from what these classes offer, and therefore would have to resort to tricky hacking, risking it to break with any new version of the framework. Or maybe you just want to be in total control of your containment and avoid having to support specialized functionality. OK, but then why not just use transitionFromViewController:toViewController:duration:options:animations:completion: and be over with it? Another good question, and you may just want to do that. But perhaps you care about your code and want to encapsulate the transition. So why not use a now-established and well-proven design pattern? And, heck, as a bonus, have support for third-party transition animations thrown in for free. The components of the iOS 7 custom view controller transition API are mostly protocols which make them extremely flexible to work with, because you can very easily plug them into your existing class hierarchy. These objects conform to the UIViewControllerContextTransitioning protocol, and are created and provided by the system. They conform to the UIViewControllerTransitionCoordinator protocol. As you know, from otherwise reading this publication, there are interactive and non-interactive transitions. In this article, we will concentrate on non-interactive transitions. This means that we will be dealing with animation controllers, transitioning delegates, and transitioning contexts from the list above. The Xcode project, in its three stages, is put in a. Stage 1: The Basics The central class in our app is ContainerViewController, which hosts an array of UIViewController instances — in our case, trivial ChildViewController objects. The container view controller sets up a private subview with tappable icons representing each child view controller: To switch between child view controllers, tap the icons. At this stage, there is no transition animation when switching child view controllers. Check out the tag to see the code for the basic app. Stage 2: Animating the Transition When adding a transition animation, we want to support animation controllers conforming to UIViewControllerAnimatedTransitioning. The protocol defines these three methods, the first two of which are required: - NSTimeInterval transitionDuration: id transitionContext; - void animateTransition: id transitionContext; - void animationEnded: BOOL transitionCompleted; This tells us everything we need to know. When our container view controller is about to perform the animation, we can query the animation controller for the duration and ask it to perform the actual animation. When it is done, we can call animationEnded: on the the animation controller, if it implements that optional method. However, there is one thing we need to figure out first. As you can see from the method signatures above, the two required ones take a transitioning context parameter, i. Normally, when using the built-in classes, the framework creates and passes on this context to our animation controller for us. But in our case, since we are acting as the framework, we need to create that object. This is where the convenience of the heavy use of protocols comes in. Instead of having to override a private class, which obviously is a no-go, we can make our own and just have it conform to the documented protocol. There are a , though, and they are all required. But we can ignore some of them for now, because we are currently only supporting non-interactive transitions. Just like UIKit, we define a private NSObject class. Notice, our initializer requires information about whether we are going right or not. In our specialized ContainerViewController context, where buttons are arranged horizontally next to each other, the transition context is recording information about their positional relationship by setting the respective frames. The animation controller, or animator, can choose to use this when composing the animation. The animator should only concern itself with the context, which is passed to it, because that would, ideally, make the animator reusable in other contexts. We will keep this in mind when making our own animation controller next, now that we have the transition context available to us. You probably remember that this was exactly what we did in ,. So why not just use that? In fact, because of the extensive use of protocols in this framework, we can take the animation controller, the Animator class, from that project and plug it right in to ours — without any modifications. Doing the animation is basically three lines of code: 1 creating the animator, 2 creating the transition context, and 3 triggering the animation. With that, the transition now looks like this: Pretty cool. This is reflected in the code with the tag. To see the full extent of the stage 2 changes, check the. This entails conveniently removing the dependency to the Animator class, as well as creating a delegate protocol. Otherwise, we will create our own private default animator of class PrivateAnimatedTransition. We will implement this next. Although the default animation is somewhat different than that of Animator, the code looks surprisingly similar. This class can therefore still be used in other codebases. The transition animation now looks like this: In the code with the tag, setting the delegate in the app delegate has been in order to see the default animation in action. Set it back in to use Animator again. You may want to check out the. We now have a self-contained ContainerViewController with a nicely animated default transition that developers can override with their own, iOS 7 custom animation controller UIViewControllerAnimatedTransitioning objects — even without needing access to our source code. Conclusion In this article we looked at making our custom container view controller a first-class UIKit citizen by integrating it with the Custom View Controller Transitions, new in iOS 7. This means you can apply your own non-interactive transition animation to our custom container view controller. We saw that because we could take an existing transition class, from seven issues ago, and plug it right in — without modification. This is perfect if you are distributing your custom container view controller as part of a library or framework, or just want your code to be reusable. Note that we only support non-interactive transitions so far. The next step is supporting interactive transitions as well. I will leave that as an exercise for you. It is somewhat more complex because we are basically mimicking the framework behavior, which is all guesswork, really.

You will learn how to implement your own UIPresentationController subclass that defines a custom layout for the presented view controller, and responds to changes to the presented view controller's preferredContentSize. Checkerboard This example implements a jesus between two view controllers in a UINavigationController. For both presenting and dismissing, herbView will always be the view that you animate. All you have to do is set up the event-handling code needed to compute that completion percentage value and update it as each new met arrives. During a presentation, the view belonging to the presenting view controller is removed when the transition completes. Not a breathtaking presentation, but completely custom. The thing that will separate view controller presentation animation View Controller from the simple or ordinary and make it something truly unique. The Transitioning Zip Object Before a transition animation begins, UIKit creates a transitioning context object and fills it with information about how to perform the animations. Set any other properties to their final values as well. Other views may be animated as part of your presentation, but the main target of your jesus is always the view being added to the view hierarchy. Build and view controller presentation animation the project to see how the app looks and feels: Tap on one of the herb images, and the details screen comes up via the standard vertical cover transition. The transition coordinator is a way to glad those changes and animate your own content at the same time.