/ Refresh

Pull to refresh/add/show custom animation written Swift

Pull to refresh/add/show custom animation written Swift

FlippingNotch

FlippingNotch is "pull to refresh/add/show" custom animation written Swift, using the iPhone X Notch.

FlippingNotch

What FlippingNotch is not

It is not a framework, it is just an Xcode project, embracing the notch.

Requirements

FlippingNotch is written in Swift 4.0 and requires an iPhone X Simulator/Device.

Tutorial

  1. Put a UICollectionView and constraint it in a ViewController.

The image below shows an example how to constraint it.

  1. Add a cell in the UICollectionView.
  1. Set up the UICollectionView in the ViewController by conforming to UICollectionViewDataSource.
class ViewController: UIViewController {

    // MARK: IBOutlets

    @IBOutlet var collectionView: UICollectionView!
    
    // MARK: Fileprivates
    fileprivate var numberOfItemsInSection = 1

    
    // MARK: Overrides

    override func viewDidLoad() {
        super.viewDidLoad()

        collectionView.dataSource = self
    }
    
}
    
// MARK: UICollectionViewDataSource

extension ViewController: UICollectionViewDataSource {
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return numberOfItemsInSection
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        
        cell.layer.cornerRadius = 10
        cell.layer.masksToBounds = true
        
        return cell
    }
}

  1. The Notch View
  • Instantiate a view that represents the notch. The notchViewBottomConstraint is used to position the notchView into the view.
   fileprivate var notchView = UIView()
   fileprivate var notchViewBottomConstraint: NSLayoutConstraint!
   fileprivate var numberOfItemsInSection = 1
  • After instantiating the notchView, add it as a subview its parent view.
     The notchView have a black background and rounded corners.
     translatesAutoResizingMaskIntoConstraints needs to be set to false because we want to use auto layout for this view rather than frame-based layout.
     Then, the notchView is constrained to the center of its parent view, with the same width as the notch, a height of (notch height - maximum scrolling offset what we want to give) and a bottom constrained to its parent view topAnchor + notch height.

private func configureNotchView() {
        self.view.addSubview(notchView)
        
        notchView.translatesAutoresizingMaskIntoConstraints = false
        notchView.backgroundColor = UIColor.black
        notchView.layer.cornerRadius = 20
        
        notchView.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).activate()
        notchView.widthAnchor.constraint(equalToConstant: Constants.notchWidth).activate()
        notchView.heightAnchor.constraint(equalToConstant: Constants.notchHeight - 
                                                           Constants.maxScrollOffset).activate()
        notchViewBottomConstraint = notchView.bottomAnchor.constraint(equalTo: self.view.topAnchor, 
                                                                      constant: Constants.notchHeight)
        notchViewBottomConstraint.activate()
    }

The result in an iPhone 8:

  1. Reacting while scrolling

(Looks clearer in an iPhone 8 what we are trying to do)

  • We want to move down the notchView while scrolling

  • To do this, first we have to conform our ViewController to UICollectionViewDelegate and call scrollViewDidScroll delegate function. In there we write the logic to move the notchView down.

  • The scrollView should scroll until it reaches the maximum scrolling offset what we want to give

  • The bottom constrained of the notchView should be increased while scrolling.

  extension ViewController: UICollectionViewDelegate {

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
    
        // Making sure that we contentOffset of the scrollView is max to maxScrollOffset
        scrollView.contentOffset.y = max(Constants.maxScrollOffset, scrollView.contentOffset.y)
        
        // Move down the notchView until we have reached our threshold
        notchViewTopConstraint.constant = Constants.notchTopOffset - min(0, scrollView.contentOffset.y)
    }
  1. Drop the view from the notch
  • When the scroll did end dragging we want to create the view that will be part of the flipping animation.

  • We create the animatableView, reset notchBottomConstraint, and move down the collectionView and drop the animatableView (notchView clone) with an animation and we round its corners.

  private func animateView() {
    
        // Create animatableView (notch clone)
        let animatableView = UIImageView(frame: notchView.frame)
        animatableView.backgroundColor = UIColor.black
        animatableView.layer.cornerRadius = self.notchView.layer.cornerRadius
        animatableView.layer.masksToBounds = true
        animatableView.frame = self.notchView.frame
        self.view.addSubview(animatableView)
        
        // Reset notchView bottom constraint
        notchViewBottomConstraint.constant = Constants.notchHeight
        
        // Move the collectionView down
        let flowLayout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
        let height = flowLayout.itemSize.height + flowLayout.minimumInteritemSpacing
        
        self.collectionView.transform = CGAffineTransform.identity.translatedBy(x: 0, y: -Constants.maxScrollOffset)

        // Dropping animation
        UIView.animate(withDuration: 0.3, delay: 0, options: [], animations: {
            let itemSize = flowLayout.itemSize
            animatableView.frame.size = CGSize(width: Constants.notchWidth, 
                                               height: (itemSize.height / itemSize.width) * Constants.notchWidth)

            // UIImage.fromColor(color), returns an image in a certain color
            animatableView.image = UIImage.fromColor(self.view.backgroundColor?.withAlphaComponent(0.2) ?? UIColor.black)
            animatableView.frame.origin.y = Constants.notchViewTopInset
            self.collectionView.transform = CGAffineTransform.identity.translatedBy(x: 0, y: height * 0.5)
        }) 
        
        // Animate the corners
        let cornerRadiusAnimation = CABasicAnimation(keyPath: "cornerRadius")
        cornerRadiusAnimation.fromValue = 16
        cornerRadiusAnimation.toValue = 10
        cornerRadiusAnimation.duration = 0.3
        animatableView.layer.add(cornerRadiusAnimation, forKey: "cornerRadius")
        animatableView.layer.cornerRadius = 10
    }
    
extension ViewController: UICollectionViewDelegate {
   
   ...

    func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
        if scrollView.contentOffset.y <= Constants.maxScrollOffset {
            animateView()
        }
    }
}
  1. Flip it
  • After dropping the view, a snapshot of the collectionview cell is taken, the image is set on the animatableView and it is flipped with an animation.
  private func animateView() {
   ...
   
        UIView.animate(withDuration: 0.3, delay: 0, options: [], animations: {
            
            ...
            
        }) { _ in
            
            // Snapshot the collectionView cell. 
            // It is easier to deal with an image of the cell than the cell itself
            // This is the reason why animatableView is an UIImageView and not a UIView.
            let item = self.collectionView.cellForItem(at: IndexPath(row: 0, section: 0))
            animatableView.image = item?.snapshotImage()
            
            // Flipping transition
            UIView.transition(with: animatableView, duration: 0.6, options: UIViewAnimationOptions.transitionFlipFromBottom, animations: {
                animatableView.frame.size = flowLayout.itemSize
                animatableView.frame.origin = CGPoint(x: (self.collectionView.frame.width - flowLayout.itemSize.width) / 2.0, 
                                                      y: self.collectionView.frame.origin.y - height * 0.5)
                self.collectionView.transform = CGAffineTransform.identity.translatedBy(x: 0, y: height)
                }, completion: { _ in
                    // Remove the animatableView
                    self.collectionView.transform = CGAffineTransform.identity
                    animatableView.removeFromSuperview()
                    
                    // Add an item in section
                    self.numberOfItemsInSection += 1
                    self.collectionView.reloadData()
                }
            )
        }
        
      ...
    }

Limitations

The animation works as expected only in iPhone X in portrait mode

TODO

  • Include the case when a NavigationBar is implemented.

GitHub