View Controller Transition animate subview position - ios

I'm trying to create a simple transition animation between two view controllers, both of which have the same label. I simply want to animate the label from its position in the first view controller, to its position in the second (see below illustration).
I have set up my view controllers to use a custom animation controller, where I have access to both view controllers and the label through an outlet.
In the animation block, I simply set the frame of the label on the first view controller to that of the label on the second view controller.
[UIView animateWithDuration:self.duration animations:^{
fromViewController.label.frame = toViewController.titleLabel.frame;
} completion:^(BOOL finished) {
[transitionContext completeTransition:finished];
}];
Instead of the intended effect of the label moving from the middle of the screen to the upper left corner, as soon as the animation begins the label is positioned in the bottom right corner and then animates to the middle.
I tried printing out the positions of the labels beforehand, which shows the same frame I see in the storyboard:
fromViewController.label.frame: {{115.5, 313}, {144, 41}}
toViewController.titleLabel.frame: {{16, 12}, {144, 41}}
I have no idea as to why I'm not getting the intended behavior, and what is happening in its place.
Any suggestions as to what I can change to make my animation run correctly and why I'm seeing this behavior would be greatly appreciated.

You mention the animation of the subviews but you don't talk about the overall animation, but I'd be inclined to use the container view for the animation, to avoid any potential confusion/problems if you're animating the subview and the main view simultaneously. But I'd be inclined to:
Make snapshots of where the subviews in the "from" view and then hide the subviews;
Make snapshots of where the subviews in the "to" view and then hide the subviews;
Convert all of these frame values to the coordinate space of the container and add all of these snapshots to the container view;
Start the "to" snapshots' alpha at zero (so they fade in);
Animate the changing of the "to" snapshots to their final destination changing their alpha back to 1.
Simultaneously animate the "from" snapshots to the location of the "to" view final destination and animate their alpha to zero (so they fade out, which combined with point 4, yields a sort of cross dissolve).
When all done, remove the snapshots and unhide the subviews whose snapshots were animated.
The net effect is a sliding of the label from one location to another, and if the initial and final content were different, yielding a cross dissolve while they're getting moved.
For example:
By using the container view for the animation of the snapshots, it's independent of any animation you might be doing of the main view of the destination scene. In this case I'm sliding it in from the right, but you can do whatever you want.
Or, you can do this with multiple subviews:
(Personally, if this were the case, where practically everything was sliding around, I'd lose the sliding animation of the main view because it's now becoming distracting, but it gives you the basic idea. Also, in my dismiss animation, I swapped around which view is being to another, which you'd never do, but I just wanted to illustrate the flexibility and the fading.)
To render the above, I used the following in Swift 4:
protocol CustomTransitionOriginator {
var fromAnimatedSubviews: [UIView] { get }
}
protocol CustomTransitionDestination {
var toAnimatedSubviews: [UIView] { get }
}
class Animator: NSObject, UIViewControllerAnimatedTransitioning {
enum TransitionType {
case present
case dismiss
}
let type: TransitionType
init(type: TransitionType) {
self.type = type
super.init()
}
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
return 1.0
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
let fromVC = transitionContext.viewController(forKey: .from) as! CustomTransitionOriginator & UIViewController
let toVC = transitionContext.viewController(forKey: .to) as! CustomTransitionDestination & UIViewController
let container = transitionContext.containerView
// add the "to" view to the hierarchy
toVC.view.frame = fromVC.view.frame
if type == .present {
container.addSubview(toVC.view)
} else {
container.insertSubview(toVC.view, belowSubview: fromVC.view)
}
toVC.view.layoutIfNeeded()
// create snapshots of label being animated
let fromSnapshots = fromVC.fromAnimatedSubviews.map { subview -> UIView in
// create snapshot
let snapshot = subview.snapshotView(afterScreenUpdates: false)!
// we're putting it in container, so convert original frame into container's coordinate space
snapshot.frame = container.convert(subview.frame, from: subview.superview)
return snapshot
}
let toSnapshots = toVC.toAnimatedSubviews.map { subview -> UIView in
// create snapshot
let snapshot = subview.snapshotView(afterScreenUpdates: true)!// UIImageView(image: subview.snapshot())
// we're putting it in container, so convert original frame into container's coordinate space
snapshot.frame = container.convert(subview.frame, from: subview.superview)
return snapshot
}
// save the "to" and "from" frames
let frames = zip(fromSnapshots, toSnapshots).map { ($0.frame, $1.frame) }
// move the "to" snapshots to where where the "from" views were, but hide them for now
zip(toSnapshots, frames).forEach { snapshot, frame in
snapshot.frame = frame.0
snapshot.alpha = 0
container.addSubview(snapshot)
}
// add "from" snapshots, too, but hide the subviews that we just snapshotted
// associated labels so we only see animated snapshots; we'll unhide these
// original views when the animation is done.
fromSnapshots.forEach { container.addSubview($0) }
fromVC.fromAnimatedSubviews.forEach { $0.alpha = 0 }
toVC.toAnimatedSubviews.forEach { $0.alpha = 0 }
// I'm going to push the the main view from the right and dim the "from" view a bit,
// but you'll obviously do whatever you want for the main view, if anything
if type == .present {
toVC.view.transform = .init(translationX: toVC.view.frame.width, y: 0)
} else {
toVC.view.alpha = 0.5
}
// do the animation
UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
// animate the snapshots of the label
zip(toSnapshots, frames).forEach { snapshot, frame in
snapshot.frame = frame.1
snapshot.alpha = 1
}
zip(fromSnapshots, frames).forEach { snapshot, frame in
snapshot.frame = frame.1
snapshot.alpha = 0
}
// I'm now animating the "to" view into place, but you'd do whatever you want here
if self.type == .present {
toVC.view.transform = .identity
fromVC.view.alpha = 0.5
} else {
fromVC.view.transform = .init(translationX: fromVC.view.frame.width, y: 0)
toVC.view.alpha = 1
}
}, completion: { _ in
// get rid of snapshots and re-show the original labels
fromSnapshots.forEach { $0.removeFromSuperview() }
toSnapshots.forEach { $0.removeFromSuperview() }
fromVC.fromAnimatedSubviews.forEach { $0.alpha = 1 }
toVC.toAnimatedSubviews.forEach { $0.alpha = 1 }
// clean up "to" and "from" views as necessary, in my case, just restore "from" view's alpha
fromVC.view.alpha = 1
fromVC.view.transform = .identity
// complete the transition
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})
}
}
// My `UIViewControllerTransitioningDelegate` will specify this presentation
// controller, which will clean out the "from" view from the hierarchy when
// the animation is done.
class PresentationController: UIPresentationController {
override var shouldRemovePresentersView: Bool { return true }
}
Then, to allow all of the above to work, if I'm transitioning from ViewController to SecondViewController, I'd specify what subviews I'm moving from and which ones I'm moving to:
extension ViewController: CustomTransitionOriginator {
var fromAnimatedSubviews: [UIView] { return [label] }
}
extension SecondViewController: CustomTransitionDestination {
var toAnimatedSubviews: [UIView] { return [label] }
}
And to support the dismiss, I'd add the converse protocol conformance:
extension ViewController: CustomTransitionDestination {
var toAnimatedSubviews: [UIView] { return [label] }
}
extension SecondViewController: CustomTransitionOriginator {
var fromAnimatedSubviews: [UIView] { return [label] }
}
Now, I don't want you to get lost in all of this code, so I'd suggest focusing on the high-level design (those first seven points I enumerated at the top). But hopefully this is enough for you to follow the basic idea.

The problem lies in dealing with coordinate systems. Consider these numbers:
fromViewController.label.frame: {{115.5, 313}, {144, 41}}
toViewController.titleLabel.frame: {{16, 12}, {144, 41}}
Those pairs of numbers are unrelated:
The frame of the label is in the bounds coordinates of its superview, probably fromViewController.view.
The frame of the titleLabel is in the bounds coordinates of its superview, probably toViewController.view.
Moreover, in most custom view transitions, the two view controller's views are in motion throughout the process. This makes it very difficult to say where the intermediate view should be at any moment in terms of either of them.
Thus you need to express the motion of this view in some common coordinate system, higher than either of those. That's why, in my answer here I use a snapshot view that's loose in the higher context view.

Related

After running a view controller custom transition back and forward the view controller stops responding (but the app doesn't crash entirely)

I have two view controllers and from the first one I show the second one by a modal segue, which presentation style is set to over current context. I also use blur effect which appears during the transition and disappears after it.
I've created a demo app to show how the transition looks like:
Here, the second view controller contains a UIScrollView, and on top of that, a yellow rectangle, which is another UIView with a UIButton on it. That UIButton also closes the view controller. Also, as you can see, I've set the background color to clear, so the blur effect is visible.
Now, in my project the transition is basically the same, except, my view controllers are "heavier".
The first view controller is embedded inside a UINavigationController" and a UITabBarController and on it I have a custom segmented control which
is made from UIViews and UIButtons, and a UITableView with custom cells.
The second view controller consists of a UIScrollView and a UIView (like on the image above, just bigger a little). That view contains a UIImageView, UILabels and a smaller UIView which is used as button to close the view by tapping on it.
Here is the code that I use to close the second view controller by dragging it down (UIScrollViewDelegate's methods).
extension AuthorInfoViewController: UIScrollViewDelegate {
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
isDragging = true
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard isDragging else {
return
}
if !isDismissingAuthorInfo && scrollView.contentOffset.y < -30.0 && dismissAnimator != nil {
authoInfoViewControllerDelegate?.authorInfoViewControllerWillDismiss()
isDismissingAuthorInfo = true
dismissAnimator?.wantsInteractiveStart = true
dismiss(animated: true, completion: nil)
return
}
if isDismissingAuthorInfo {
let progress = max(0.0, min(1.0, ((-scrollView.contentOffset.y) - 30) / 90.0))
dismissAnimator?.update(progress)
}
}
func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
let progress = max(0.0, min(1.0, ((-scrollView.contentOffset.y) - 30) / 90.0))
if progress > 0.5 {
dismissAnimator?.finish()
} else {
dismissAnimator?.cancel()
print("Canceled")
}
isDismissingAuthorInfo = false
isDragging = false
}
}
Here, isDismissingAuthorInfo and isDragging are booleans which keep
track whether the view is dismissing and is dragged at all. authorInfoViewControllerWillDismiss is a method implemented in a protocol to which conforms the first view controller. That methods calls another method which adds the blur animation to the custom transitions animator.
EDITED
The animator code is the following:
class DismissAnimator: UIPercentDrivenInteractiveTransition, UIViewControllerAnimatedTransitioning {
var auxAnimationsForBlur: (()->Void)?
var auxAnimationsForTabBar: (()->Void)?
var auxAnimationsCancelForBlur: (()->Void)?
var auxAnimationsCancelForTabBar: (()->Void)?
var tabBar: UITabBar?
var blurView: UIView?
let transitionDuration = 0.75
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
return transitionDuration
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
transitionAnimator(using: transitionContext).startAnimation()
}
func transitionAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating {
let duration = transitionDuration(using: transitionContext)
let container = transitionContext.containerView
let from = transitionContext.view(forKey: .from)!
container.addSubview(from)
let animator = UIViewPropertyAnimator(duration: duration, curve: .easeOut)
animator.addAnimations({
from.transform = CGAffineTransform(translationX: 0.0, y: container.frame.size.height + 30)
}, delayFactor: 0.15)
animator.addCompletion { (position) in
switch position {
case .end:
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
self.tabBar?.isHidden = false
self.blurView?.removeFromSuperview()
default:
transitionContext.completeTransition(false)
self.auxAnimationsCancelForBlur?()
self.auxAnimationsCancelForTabBar?()
}
}
if let auxAnimationsForBlur = auxAnimationsForBlur {
animator.addAnimations(auxAnimationsForBlur)
}
if let auxAnimationsForTabBar = auxAnimationsForTabBar {
animator.addAnimations(auxAnimationsForTabBar)
}
return animator
}
func interruptibleAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating {
return transitionAnimator(using:transitionContext)
}
}
In the code above, the auxAnimationsForBlur is for adding blur animation to the animator, the auxAnimationsCancelForBlur is for canceling it, auxAnimationsForTabBar is for adding the animation of alpha value of tabBar, auxAnimationsCancelForTabBar is for canceling it.
Now, the problem is the following: the animation works fine, but after running it by dragging the second view controller for several times (5-9, approximately), after the transition is over and the first view controller is shown, it just stops responding. However, on the bottom I have a tab bar, and it works. So, when I change to another tab and return back, I see the second view controller and a black screen behind it (where the first view controller should have been). When this happens the cancel method on UIPercentDrivenInteractiveTransition gets called, from scrollViewWillEndDragging method above (on the console I see the word cancel printed). Is it possible that cancel method on UIPercentDrivenInteractiveTransition doesn't causes this problem, because when I comment out the call to that method, it seems everything works ok (in that case, I also comment out the call to interruptibleAnimator(using:) method on my animator, so I lose the interactive behaviour of the transition)? I couldn't reproduce this behaviour while closing the second view controller by tapping on a close button, so I think it has something to do with dragging.
What could cause this problem, and what could you suggest for solving it? I would appreciate all your help.

How can return UIView views along with its subviews in swift?

I want to create a stack of rounded circle views like this.
UIView stack
I want to return this whole stack of UIViews at once. So I tried in this way.
open func setupCirclestack(parentFrame:CGRect)->UIView
{
let arrayColor=[UIColor.yellow,UIColor.blue,UIColor.red]
let baseCircle=Circle.init(frame: parentFrame)
baseCircle.backgroundColor=UIColor.purple
var parentview=baseCircle
// var existingFrame=baseCircle.frame
for i in 0...2//<CircleValues().numberOfCircles-1
{
let circle=self.getInnerCircle(currentFrame: parentFrame)
circle.backgroundColor=arrayColor[i]
parentview.addSubview(circle)
parentview=circle as! Circle
//existingFrame=circle.frame
}
return parentview
}
func getInnerCircle(currentFrame:CGRect)->UIView
{
CircleValues.sharedInstance.radius=CircleValues.sharedInstance.radius-30
print("New Radius------\(CircleValues.sharedInstance.radius)")
let circle=Circle.init(frame: currentFrame)
return circle
}
But I can get only the last (inner most view) view. How can I return the whole stack of UIViews from this method
It is because your all the frames for all the circles are same as parentFrame.
So, your all views are adding but you can only able to see last view as it is overlaps other views!
You have to decrease your frame size for every iteration of your for loop for every child view you are adding!
for i in 0...2//<CircleValues().numberOfCircles-1
{
let circle=self.getInnerCircle(currentFrame: parentFrame) // decrease size(height and width) here every time to achieve result attached in screenshot in your question
circle.backgroundColor=arrayColor[i]
parentview.addSubview(circle)
parentview=circle as! Circle
//existingFrame=circle.frame
}
You reasign a parentView variable at the end of for loop, So it will replace existing object of parentView in which you added the circle as a subview. Therefore it will return a last circle object which is stored in parentView.
for i in 0...2//<CircleValues().numberOfCircles-1
{
let circle=self.getInnerCircle(currentFrame: parentFrame)
circle.backgroundColor=arrayColor[i]
parentview.addSubview(circle)
//parentview=circle as! Circle
//existingFrame=circle.frame
}
If you want to return views inside your parent view you need to change your function to something like this:
open func setupCirclestack(parentFrame:CGRect)->UIView
{
let arrayColor=[UIColor.yellow,UIColor.blue,UIColor.red]
let baseCircle=Circle.init(frame: parentFrame)
baseCircle.backgroundColor=UIColor.purple
var parentview=baseCircle
// var existingFrame=baseCircle.frame
for i in 0...2//<CircleValues().numberOfCircles-1
{
let circle=self.getInnerCircle(currentFrame: parentFrame)
circle.backgroundColor=arrayColor[i]
parentview.addSubview(circle)
}
return parentview
}
But if you need to return array of views, try this:
open func setupCirclestack(parentFrame:CGRect)->[UIView]
{
let arrayColor = [UIColor.yellow,UIColor.blue,UIColor.red]
let baseCircle = Circle.init(frame: parentFrame)
baseCircle.backgroundColor=UIColor.purple
var circleArray = [Circle]()
for i in 0...2
{
let circle = self.getInnerCircle(currentFrame: parentFrame)
circle.backgroundColor = arrayColor[i]
circleArray.append(circle)
}
return circleArray
}

How to replicate the drop/bounce animation effect as seen in iOS Notification Center window?

How would one replicate the bounce effect of the iOS Notification Center window that drops to the bottom of the screen and bounces without ever traveling below the height of the window? This appears to use damping and spring velocity but how do you prevent the object, such as in this case, from overshooting its mark and slinging back?
Take a look into UIKitDynamics. This will allow you to apply physics and collisions to your views.
You could have a view that drops from the top of the screen and collides with a view at the bottom of the screen. You'll need to use UIGravityBehavior and UICollisionBehavior, and should be able to adjust the constants to get the desired effect.
Updated answer: You could build your own custom transition.
Say you have two view controllers, StartController and EndController. You want to have this custom transition to happen from StartController to EndController.
1) Create your custom transition object like so:
class CustomSlideTransition: NSObject, UIViewControllerAnimatedTransitioning {
var duration: Double = 1.0
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
return duration
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
// Access EndController
let toViewController = transitionContext.viewController(forKey: .to) as! EndController
// Access the container view :
let containerView = transitionContext.containerView
// Move EndController's view frame:
toViewController.view.frame.origin.y -= UIScreen.main.bounds.size.height
containerView.addSubview(toViewController.view)
// Adjust the properties of the spring to what fits your needs the most:
UIView.animate(withDuration: duration, delay: 0.0, usingSpringWithDamping: 0.2, initialSpringVelocity: 7.0, options: [.curveEaseInOut], animations: {
// Get your EndController's view frame moves back to its final position
toViewController.view.frame.origin.y += UIScreen.main.bounds.size.height
}, completion: { (finished) in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})
}
}
2) In the prepareForSegue method of your StartController, set the delegate to self :
class StartController: UIViewController {
// ...
// MARK: PrepareForSegue
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destinationController = segue.destination as? EndController {
destinationController.transitioningDelegate = self
}
}
// ...
}
3) Make StartController conform to the UIViewControllerTransitioningDelegate :
extension StartController: UIViewControllerTransitioningDelegate {
// MARK: UIViewControllerTransitioningDelegate
func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return CustomSlideTransition()
}
}
4) Design your EndController however you want!
Note: You may want to add a custom transition for dismissing EndController as well.
Update: Now if you really don't want your view controller to bounce even a little beyond the window, using a spring here may not be the best way to go.
Since on iPhone the bounces effect "power" is calculated using the swipe (from the top) offset, you might want to custom even more your animation block using key frame animations, or UIKIT Dynamics if you're comfortable with.
UIView.animate(withDuration: duration, animations: {
toViewController.view.frame.origin.y += UIScreen.main.bounds.size.height
}, completion: { (finished) in
// Create a custom bounce effect that doesn't go beyond the window (ie. only negative values)
let animation = CAKeyframeAnimation(keyPath: "transform.translation.y")
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
animation.duration = 0.75
animation.autoreverses = false
// Depending on how you would like to present EndController, you may want to change the hardcoded values below.
// For example you could make it so that if the user swipes really fast, it would bounce even more..
animation.values = [0, -60, 0, -25, 0]
// Add the key frame animation to the view's layer :
toViewController.view.layer.add(animation, forKey: "bounce")
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})

How can I mimic the bottom sheet from the Maps app?

Can anyone tell me how I can mimic the bottom sheet in the new Apple Maps app in iOS 10?
In Android, you can use a BottomSheet which mimics this behaviour, but I could not find anything like that for iOS.
Is that a simple scroll view with a content inset, so that the search bar is at the bottom?
I am fairly new to iOS programming so if someone could help me creating this layout, that would be highly appreciated.
This is what I mean by "bottom sheet":
I don't know how exactly the bottom sheet of the new Maps app, responds to user interactions. But you can create a custom view that looks like the one in the screenshots and add it to the main view.
I assume you know how to:
1- create view controllers either by storyboards or using xib files.
2- use googleMaps or Apple's MapKit.
Example
1- Create 2 view controllers e.g, MapViewController and BottomSheetViewController. The first controller will host the map and the second is the bottom sheet itself.
Configure MapViewController
Create a method to add the bottom sheet view.
func addBottomSheetView() {
// 1- Init bottomSheetVC
let bottomSheetVC = BottomSheetViewController()
// 2- Add bottomSheetVC as a child view
self.addChildViewController(bottomSheetVC)
self.view.addSubview(bottomSheetVC.view)
bottomSheetVC.didMoveToParentViewController(self)
// 3- Adjust bottomSheet frame and initial position.
let height = view.frame.height
let width = view.frame.width
bottomSheetVC.view.frame = CGRectMake(0, self.view.frame.maxY, width, height)
}
And call it in viewDidAppear method:
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
addBottomSheetView()
}
Configure BottomSheetViewController
1) Prepare background
Create a method to add blur and vibrancy effects
func prepareBackgroundView(){
let blurEffect = UIBlurEffect.init(style: .Dark)
let visualEffect = UIVisualEffectView.init(effect: blurEffect)
let bluredView = UIVisualEffectView.init(effect: blurEffect)
bluredView.contentView.addSubview(visualEffect)
visualEffect.frame = UIScreen.mainScreen().bounds
bluredView.frame = UIScreen.mainScreen().bounds
view.insertSubview(bluredView, atIndex: 0)
}
call this method in your viewWillAppear
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
prepareBackgroundView()
}
Make sure that your controller's view background color is clearColor.
2) Animate bottomSheet appearance
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
UIView.animateWithDuration(0.3) { [weak self] in
let frame = self?.view.frame
let yComponent = UIScreen.mainScreen().bounds.height - 200
self?.view.frame = CGRectMake(0, yComponent, frame!.width, frame!.height)
}
}
3) Modify your xib as you want.
4) Add Pan Gesture Recognizer to your view.
In your viewDidLoad method add UIPanGestureRecognizer.
override func viewDidLoad() {
super.viewDidLoad()
let gesture = UIPanGestureRecognizer.init(target: self, action: #selector(BottomSheetViewController.panGesture))
view.addGestureRecognizer(gesture)
}
And implement your gesture behaviour:
func panGesture(recognizer: UIPanGestureRecognizer) {
let translation = recognizer.translationInView(self.view)
let y = self.view.frame.minY
self.view.frame = CGRectMake(0, y + translation.y, view.frame.width, view.frame.height)
recognizer.setTranslation(CGPointZero, inView: self.view)
}
Scrollable Bottom Sheet:
If your custom view is a scroll view or any other view that inherits from, so you have two options:
First:
Design the view with a header view and add the panGesture to the header. (bad user experience).
Second:
1 - Add the panGesture to the bottom sheet view.
2 - Implement the UIGestureRecognizerDelegate and set the panGesture delegate to the controller.
3- Implement shouldRecognizeSimultaneouslyWith delegate function and disable the scrollView isScrollEnabled property in two case:
The view is partially visible.
The view is totally visible, the scrollView contentOffset property is 0 and the user is dragging the view downwards.
Otherwise enable scrolling.
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
let gesture = (gestureRecognizer as! UIPanGestureRecognizer)
let direction = gesture.velocity(in: view).y
let y = view.frame.minY
if (y == fullView && tableView.contentOffset.y == 0 && direction > 0) || (y == partialView) {
tableView.isScrollEnabled = false
} else {
tableView.isScrollEnabled = true
}
return false
}
NOTE
In case you set .allowUserInteraction as an animation option, like in the sample project, so you need to enable scrolling on the animation completion closure if the user is scrolling up.
Sample Project
I created a sample project with more options on this repo which may give you better insights about how to customise the flow.
In the demo, addBottomSheetView() function controls which view should be used as a bottom sheet.
Sample Project Screenshots
- Partial View
- FullView
- Scrollable View
Update iOS 15
In iOS 15, you can now use the native UISheetPresentationController.
if let sheet = viewControllerToPresent.sheetPresentationController {
sheet.detents = [.medium(), .large()]
// your sheet setup
}
present(viewControllerToPresent, animated: true, completion: nil)
Notice that you can even reproduce its navigation stack using the overcurrentcontext presentation mode:
let nextViewControllerToPresent: UIViewController = ...
nextViewControllerToPresent.modalPresentationStyle = .overCurrentContext
viewControllerToPresent.present(nextViewControllerToPresent, animated: true, completion: nil)
Legacy
I released a library based on my answer below.
It mimics the Shortcuts application overlay. See this article for details.
The main component of the library is the OverlayContainerViewController. It defines an area where a view controller can be dragged up and down, hiding or revealing the content underneath it.
let contentController = MapsViewController()
let overlayController = SearchViewController()
let containerController = OverlayContainerViewController()
containerController.delegate = self
containerController.viewControllers = [
contentController,
overlayController
]
window?.rootViewController = containerController
Implement OverlayContainerViewControllerDelegate to specify the number of notches wished:
enum OverlayNotch: Int, CaseIterable {
case minimum, medium, maximum
}
func numberOfNotches(in containerViewController: OverlayContainerViewController) -> Int {
return OverlayNotch.allCases.count
}
func overlayContainerViewController(_ containerViewController: OverlayContainerViewController,
heightForNotchAt index: Int,
availableSpace: CGFloat) -> CGFloat {
switch OverlayNotch.allCases[index] {
case .maximum:
return availableSpace * 3 / 4
case .medium:
return availableSpace / 2
case .minimum:
return availableSpace * 1 / 4
}
}
SwiftUI (12/29/20)
A SwiftUI version of the library is now available.
Color.red.dynamicOverlay(Color.green)
Previous answer
I think there is a significant point that is not treated in the suggested solutions: the transition between the scroll and the translation.
In Maps, as you may have noticed, when the tableView reaches contentOffset.y == 0, the bottom sheet either slides up or goes down.
The point is tricky because we can not simply enable/disable the scroll when our pan gesture begins the translation. It would stop the scroll until a new touch begins. This is the case in most of the proposed solutions here.
Here is my try to implement this motion.
Starting point: Maps App
To start our investigation, let's visualize the view hierarchy of Maps (start Maps on a simulator and select Debug > Attach to process by PID or Name > Maps in Xcode 9).
It doesn't tell how the motion works, but it helped me to understand the logic of it. You can play with the lldb and the view hierarchy debugger.
Our view controller stacks
Let's create a basic version of the Maps ViewController architecture.
We start with a BackgroundViewController (our map view):
class BackgroundViewController: UIViewController {
override func loadView() {
view = MKMapView()
}
}
We put the tableView in a dedicated UIViewController:
class OverlayViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
lazy var tableView = UITableView()
override func loadView() {
view = tableView
tableView.dataSource = self
tableView.delegate = self
}
[...]
}
Now, we need a VC to embed the overlay and manage its translation.
To simplify the problem, we consider that it can translate the overlay from one static point OverlayPosition.maximum to another OverlayPosition.minimum.
For now it only has one public method to animate the position change and it has a transparent view:
enum OverlayPosition {
case maximum, minimum
}
class OverlayContainerViewController: UIViewController {
let overlayViewController: OverlayViewController
var translatedViewHeightContraint = ...
override func loadView() {
view = UIView()
}
func moveOverlay(to position: OverlayPosition) {
[...]
}
}
Finally we need a ViewController to embed the all:
class StackViewController: UIViewController {
private var viewControllers: [UIViewController]
override func viewDidLoad() {
super.viewDidLoad()
viewControllers.forEach { gz_addChild($0, in: view) }
}
}
In our AppDelegate, our startup sequence looks like:
let overlay = OverlayViewController()
let containerViewController = OverlayContainerViewController(overlayViewController: overlay)
let backgroundViewController = BackgroundViewController()
window?.rootViewController = StackViewController(viewControllers: [backgroundViewController, containerViewController])
The difficulty behind the overlay translation
Now, how to translate our overlay?
Most of the proposed solutions use a dedicated pan gesture recognizer, but we actually already have one : the pan gesture of the table view.
Moreover, we need to keep the scroll and the translation synchronised and the UIScrollViewDelegate has all the events we need!
A naive implementation would use a second pan Gesture and try to reset the contentOffset of the table view when the translation occurs:
func panGestureAction(_ recognizer: UIPanGestureRecognizer) {
if isTranslating {
tableView.contentOffset = .zero
}
}
But it does not work. The tableView updates its contentOffset when its own pan gesture recognizer action triggers or when its displayLink callback is called. There is no chance that our recognizer triggers right after those to successfully override the contentOffset.
Our only chance is either to take part of the layout phase (by overriding layoutSubviews of the scroll view calls at each frame of the scroll view) or to respond to the didScroll method of the delegate called each time the contentOffset is modified. Let's try this one.
The translation Implementation
We add a delegate to our OverlayVC to dispatch the scrollview's events to our translation handler, the OverlayContainerViewController :
protocol OverlayViewControllerDelegate: class {
func scrollViewDidScroll(_ scrollView: UIScrollView)
func scrollViewDidStopScrolling(_ scrollView: UIScrollView)
}
class OverlayViewController: UIViewController {
[...]
func scrollViewDidScroll(_ scrollView: UIScrollView) {
delegate?.scrollViewDidScroll(scrollView)
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
delegate?.scrollViewDidStopScrolling(scrollView)
}
}
In our container, we keep track of the translation using a enum:
enum OverlayInFlightPosition {
case minimum
case maximum
case progressing
}
The current position calculation looks like :
private var overlayInFlightPosition: OverlayInFlightPosition {
let height = translatedViewHeightContraint.constant
if height == maximumHeight {
return .maximum
} else if height == minimumHeight {
return .minimum
} else {
return .progressing
}
}
We need 3 methods to handle the translation:
The first one tells us if we need to start the translation.
private func shouldTranslateView(following scrollView: UIScrollView) -> Bool {
guard scrollView.isTracking else { return false }
let offset = scrollView.contentOffset.y
switch overlayInFlightPosition {
case .maximum:
return offset < 0
case .minimum:
return offset > 0
case .progressing:
return true
}
}
The second one performs the translation. It uses the translation(in:) method of the scrollView's pan gesture.
private func translateView(following scrollView: UIScrollView) {
scrollView.contentOffset = .zero
let translation = translatedViewTargetHeight - scrollView.panGestureRecognizer.translation(in: view).y
translatedViewHeightContraint.constant = max(
Constant.minimumHeight,
min(translation, Constant.maximumHeight)
)
}
The third one animates the end of the translation when the user releases its finger. We calculate the position using the velocity & the current position of the view.
private func animateTranslationEnd() {
let position: OverlayPosition = // ... calculation based on the current overlay position & velocity
moveOverlay(to: position)
}
Our overlay's delegate implementation simply looks like :
class OverlayContainerViewController: UIViewController {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard shouldTranslateView(following: scrollView) else { return }
translateView(following: scrollView)
}
func scrollViewDidStopScrolling(_ scrollView: UIScrollView) {
// prevent scroll animation when the translation animation ends
scrollView.isEnabled = false
scrollView.isEnabled = true
animateTranslationEnd()
}
}
Final problem: dispatching the overlay container's touches
The translation is now pretty efficient. But there is still a final problem: the touches are not delivered to our background view. They are all intercepted by the overlay container's view.
We can not set isUserInteractionEnabled to false because it would also disable the interaction in our table view. The solution is the one used massively in the Maps app, PassThroughView:
class PassThroughView: UIView {
override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
let view = super.hitTest(point, with: event)
if view == self {
return nil
}
return view
}
}
It removes itself from the responder chain.
In OverlayContainerViewController:
override func loadView() {
view = PassThroughView()
}
Result
Here is the result:
You can find the code here.
Please if you see any bugs, let me know ! Note that your implementation can of course use a second pan gesture, specially if you add a header in your overlay.
Update 23/08/18
We can replace scrollViewDidEndDragging with
willEndScrollingWithVelocity rather than enabling/disabling the scroll when the user ends dragging:
func scrollView(_ scrollView: UIScrollView,
willEndScrollingWithVelocity velocity: CGPoint,
targetContentOffset: UnsafeMutablePointer<CGPoint>) {
switch overlayInFlightPosition {
case .maximum:
break
case .minimum, .progressing:
targetContentOffset.pointee = .zero
}
animateTranslationEnd(following: scrollView)
}
We can use a spring animation and allow user interaction while animating to make the motion flow better:
func moveOverlay(to position: OverlayPosition,
duration: TimeInterval,
velocity: CGPoint) {
overlayPosition = position
translatedViewHeightContraint.constant = translatedViewTargetHeight
UIView.animate(
withDuration: duration,
delay: 0,
usingSpringWithDamping: velocity.y == 0 ? 1 : 0.6,
initialSpringVelocity: abs(velocity.y),
options: [.allowUserInteraction],
animations: {
self.view.layoutIfNeeded()
}, completion: nil)
}
Try Pulley:
Pulley is an easy to use drawer library meant to imitate the drawer
in iOS 10's Maps app. It exposes a simple API that allows you to use
any UIViewController subclass as the drawer content or the primary
content.
https://github.com/52inc/Pulley
I wrote my own library to achieve the intended behaviour in ios Maps app. It is a protocol oriented solution. So you don't need to inherit any base class instead create a sheet controller and configure as you wish. It also supports inner navigation/presentation with or without UINavigationController.
See below link for more details.
https://github.com/OfTheWolf/UBottomSheet
You can try my answer https://github.com/SCENEE/FloatingPanel. It provides a container view controller to display a "bottom sheet" interface.
It's easy to use and you don't mind any gesture recognizer handling! Also you can track a scroll view's(or the sibling view) in a bottom sheet if needed.
This is a simple example. Please note that you need to prepare a view controller to display your content in a bottom sheet.
import UIKit
import FloatingPanel
class ViewController: UIViewController {
var fpc: FloatingPanelController!
override func viewDidLoad() {
super.viewDidLoad()
fpc = FloatingPanelController()
// Add "bottom sheet" in self.view.
fpc.add(toParent: self)
// Add a view controller to display your contents in "bottom sheet".
let contentVC = ContentViewController()
fpc.set(contentViewController: contentVC)
// Track a scroll view in "bottom sheet" content if needed.
fpc.track(scrollView: contentVC.tableView)
}
...
}
Here is another example code to display a bottom sheet to search a location like Apple Maps.
iOS 15 in 2021 adds UISheetPresentationController, which is Apple's first public release of an Apple Maps-style "bottom sheet":
UISheetPresentationController
UISheetPresentationController lets you present your view controller as a sheet. Before you present your view controller, configure its sheet presentation controller with the behavior and appearance you want for your sheet.
Sheet presentation controllers specify a sheet's size based on a detent, a height where a sheet naturally rests. Detents allow a sheet to resize from one edge of its fully expanded frame while the other three edges remain fixed. You specify the detents that a sheet supports using detents, and monitor its most recently selected detent using selectedDetentIdentifier.
https://developer.apple.com/documentation/uikit/uisheetpresentationcontroller
This new bottom sheet control is explored in WWDC Session 10063: Customize and Resize Sheets in UIKit
Unfortunately....
In iOS 15, the UISheetPresentationController has launched with only medium and large detents.
A small detent is notably absent from the iOS 15 API, which would be required to display an always-presented "collapsed" bottom sheet like Apple Maps:
Custom smaller Detents in UISheetPresentationController?
The medium detent was released to handle use cases such as the Share Sheet or the "••• More" menu in Mail: a button-triggered half sheet.
In iOS 15, Apple Maps is now using this UIKit sheet presentation rather than a custom implementation, which is a huge step in the right direction. Apple Maps in iOS 15 continues to show the "small" bar, as well as a 1/3rd height bar. But those view sizes are not public API available to developers.
UIKit engineers at the WWDC 2021 Labs seemed to know that a small detent would be a hugely popular UIKit component. I would expect to see an API expansion for iOS 16 next year.
We’ve just released a pure Swift Package supporting iOS 11.4+ which provides you a BottomSheet with theme and behavior options you can customize. This component is easy to use, and flexible. You can find it here: https://github.com/LunabeeStudio/LBBottomSheet.
A demo project is available in this repository too.
For example, it supports different ways to manage the needed height, and also adds to the controller behind it the ability to detect height changes and adapt its bottom content inset.
You can find more information on the GitHub repository and in the documentation: https://lbbottomsheet.lunabee.studio.
I think it can help you to do what you’re looking for. Don’t hesitate to tell me if you have comments/questions :)
Here you can see one of all the possible BottomSheet configurations:
**for iOS 15 Native Support available for this **
#IBAction func openSheet() {
let secondVC = self.storyboard?.instantiateViewController(withIdentifier: "SecondViewController")
// Create the view controller.
if #available(iOS 15.0, *) {
let formNC = UINavigationController(rootViewController: secondVC!)
formNC.modalPresentationStyle = UIModalPresentationStyle.pageSheet
guard let sheetPresentationController = formNC.presentationController as? UISheetPresentationController else {
return
}
sheetPresentationController.detents = [.medium(), .large()]
sheetPresentationController.prefersGrabberVisible = true
present(formNC, animated: true, completion: nil)
} else {
// Fallback on earlier versions
}
}
iOS 15 finally adds a native UISheetPresentationController!
Official documentation
https://developer.apple.com/documentation/uikit/uisheetpresentationcontroller
I recently created a component called SwipeableView as subclass of UIView, written in Swift 5.1 . It support all 4 direction, has several customisation options and can animate and interpolate different attributes and items ( such as layout constraints, background/tint color, affine transform, alpha channel and view center, all of them demoed with the respective show case ). It also supports the swiping coordination with the inner scroll view if set or auto detected. Should be pretty easy and straightforward to be used ( I hope 🙂)
Link at https://github.com/LucaIaco/SwipeableView
proof of concept:
Hope it helps
If you are looking for a SwiftUI 2.0 solution that uses View Struct, here it is:
https://github.com/kenfai/KavSoft-Tutorials-iOS/tree/main/MapsBottomSheet
Maybe you can try my answer https://github.com/AnYuan/AYPannel, inspired by Pulley. Smooth transition from moving the drawer to scrolling the list. I added a pan gesture on the container scroll view, and set shouldRecognizeSimultaneouslyWithGestureRecognizer to return YES. More detail in my github link above. Wish to help.

Animating changes to presentingViewController during interactive dismissal

I'm working on a UIPresentationController subclass similar to Mail.app's open draft behavior. When a view controller is presented, it doesn't go all the way to the top and the presenting view controller scales down as if it were falling back.
The basic gist of it is below:
class CustomPresentationController : UIPresentationController {
// Create a 40pt space above the view.
override func frameOfPresentedViewInContainerView() -> CGRect {
let frame = super.frameOfPresentedViewInContainerView()
let insets = UIEdgeInsets(top: 40, left: 0, bottom: 0, right: 0)
return UIEdgeInsetsInsetRect(frame, insets)
}
// Scale down when expanded is true, otherwise identity.
private func setScale(expanded expanded: Bool) {
if expanded {
let fromMeasurement = presentingViewController.view.bounds.width
let fromScale = (fromMeasurement - 30) / fromMeasurement
presentingViewController.view.transform = CGAffineTransformMakeScale(fromScale, fromScale)
} else {
presentingViewController.view.transform = CGAffineTransformIdentity
}
}
// Scale down alongside the presentation.
override func presentationTransitionWillBegin() {
presentingViewController.transitionCoordinator()?.animateAlongsideTransition({ context in
self.setScale(expanded: true)
}, completion: { context in
self.setScale(expanded: !context.isCancelled())
})
}
// Scale up alongside the dismissal.
override func dismissalTransitionWillBegin() {
presentingViewController.transitionCoordinator()?.animateAlongsideTransition({ context in
self.setScale(expanded: false)
}, completion: { context in
self.setScale(expanded: context.isCancelled())
})
}
// Fix the scaled view's frame on orientation change.
override func containerViewWillLayoutSubviews() {
super.containerViewWillLayoutSubviews()
guard let bounds = containerView?.bounds else { return }
presentingViewController.view.bounds = bounds
}
}
This works fine for a non-interactive presentation or dismissal. When performing an interactive dismissal, however, all animations on presentingViewController.view run non-interactively. That is, the scaling will happen in the ~300ms it normally takes to dismiss rather than staying at 3% complete when 3% dismissed.
You can see this in a sample project is available on GitHub. and a video of the issue is on YouTube.
I've tried the following approaches but they all yield the same result:
A parallel animation as seen above.
Animating in the UIViewControllerAnimatedTransitioning.
Using a CABasicAnimation an manually adjusting the timing of the container view's layer.
The problem was that presentingViewController is not a descendent of the presentation's containerView. UIPercentDrivenInteractiveTransition works by setting containerView.layer.speed to zero and setting containerView.layer.timeOffset to reflect the percent complete. Since the view in question was not part of the hierarchy, its speed stayed at 1 and it completed as normal.
This is explicitly stated in the documentation for animateAlongsideTransition(_:,completion:):
Use this method to perform animations that are not handled by the animator objects themselves. All of the animations you specify must occur inside the animation context’s container view (or one of its descendants). Use the containerView property of the context object to get the container view. To perform animations in a view that does not descend from the container view, use the animateAlongsideTransitionInView:animation:completion: method instead.
As the documentation indicates, switching to animateAlongsideTransitionInView(_:,animation:,completion:) fixes the problem:
// Scale up alongside the dismissal.
override func dismissalTransitionWillBegin() {
presentingViewController.transitionCoordinator()?.animateAlongsideTransitionInView(presentingViewController.view, animation: { context in
self.setScale(expanded: false)
}, completion: { context in
self.setScale(expanded: context.isCancelled())
})
}
The comment on that method in the header is a lot more direct about this than the documentation:
// This alternative API is needed if the view is not a descendent of the container view AND you require this animation to be driven by a UIPercentDrivenInteractiveTransition interaction controller.
Thank you for the answer, had this issue on iOS 9.x and 10.x devices - using animateAlongsideTransition(in:animation:completion:) did the job.
Interestingly, on iOS 11.x animate(alongsideTransition:completion:) works correctly for presentingViewController too (there is no need to use animateAlongsideTransition(in:animation:completion:)) - looks like Apple lifted something under the hood in the latest iOS.

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