What Flipping Notch
Flipping Notch is not a framework, it is just an Xcode project, embracing the notch.
1. Put a UICollectionView and constraint it in a ViewController.
The image below shows an example how to constraint it.
2. Add a cell in the UICollectionView.
3. Set up the UICollectionView in the ViewController by conforming to UICollectionViewDataSource.
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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 } } |
4. The Notch View
- Instantiate a view that represents the notch. The
notchViewBottomConstraintis used to position the notchView into the view.
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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.
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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:
5. 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
scrollViewDidScrolldelegate 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 will increase while scrolling.
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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) } |
6. 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 thecollectionViewand drop the animatableView (notchView clone) with an animation and we round its corners.
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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() } } } |
7. Flip it
- After dropping the view, a snapshot of the
collectionview cellis taken, the image is set on theanimatableViewand it is flipped with an animation.
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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
- when you implement a NavigationBar please include the case.
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