LazyTransitions

A simple framework that allows you to create similar lazy pops and dismisses like in the Facebook, Instagram or Twitter apps.

Installation

CocoaPods

Add the following line to your PodFile:

pod 'LazyTransitions' , :git => 'https://github.com/serp1412/LazyTransitions.git'

Usage

The simplest way to use this framework is to take advantage of UniversalTransitionsHandler class.

You can just give it the views in your view controller that will trigger a transition when the user swipes on them. It could be a simple static view. Or a scroll view that will trigger the transition when it reaches the edges of it's content.

Import the framework

import LazyTransitions

Create an instance of UniversalTransitionsHandler

let transitioner = UniversalTransitionsHandler()

Pass your transition views (views that will trigger a transition when user pans on them) to the handler

transitioner.addTransition(for: view)
// or
transitioner.addTransition(for: scrollView)

In the beginTransitionAction trigger your transition (dismiss or pop)

transitioner.beginTransitionAction = { [weak self] _ in
    self?.dismiss(animated: true, completion: nil)
}

In your transitioning delegate methods pass the animator and interactor from the transition handler

func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    // ... pass the animator
    return transitioner.animator
}
    
func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
    // ... pass the interactor
    return transitioner.interactor
}

Example

Here's some sample code on how to use LazyTransitions in your project.

// first of all import LazyTransitions
import LazyTransitions

class MyVC : UIViewController {
    fileprivate let transitioner = UniversalTransitionsHandler()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // add the main view to your transition handler
        transitioner.addTransition(for: view)
        
        // trigger the transition in beginTransitionAction
        transitioner.beginTransitionAction = { [weak self] _ in
            // for dismiss
            self?.dismiss(animated: true, completion: nil)
            // or for pop
            _ = self?.navigationController?.popViewController(animated: true)
        }
        
        // FOR DISMISS
        // become your delegate for custom view controller transitioning
        transitioningDelegate = self
        
        // or FOR POP
        // become the delegate for your navigation controller
        navigationController.delegate = self
    }
}

// FOR DISMISS
// in the view controller's transitioning methods...
extension MyVC : UIViewControllerTransitioningDelegate {
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        // ... pass the animator
        return transitioner.animator
    }
    
    func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        // ... pass the interactor
        return transitioner.interactor
    }
}

// FOR POP
// in the navigation controller's delegate methods
extension MyVC : UINavigationControllerDelegate {
    func navigationController(_ navigationController: UINavigationController,
                              animationControllerFor operation: UINavigationControllerOperation,
                              from fromVC: UIViewController,
                              to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        guard operation == .pop else { return nil }
        // ... pass the animator if the operation is pop
        return transitioner.animator
    }
    
    func navigationController(_ navigationController: UINavigationController, 
                              interactionControllerFor animationController: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        // ... pass the interactor
        return transitioner.interactor
    }
}

Usage Tips

To add the a bouncy effect when user scrolls with inertia and the UIScrollView reaches its edges, do the following:

// become the delegate of your UIScrollView
scrollView.delegate = self

// implement the scrollViewDidScroll() delegate method
func scrollViewDidScroll(_ scrollView: UIScrollView) {
    // forward it to the transitioner
    transitioner.didScroll(scrollView)
}

To achieve the standard pop animation of iOS, use the provided PopAnimator when initializing the UniversalTransitionsHandler

let transitioner = UniversalTransitionsHandler(animator: PopAnimator(orientation: .leftToRight))

You can limit the allowed transition orientations by setting them like this:

transitioner.allowedOrientations = [.leftToRight, .topToBottom, .bottomToTop]

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