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I'm having the hardest time implementing a presentation of a drawer sliding partway up on the screen on iPhone.

EDIT: I've discovered that iOS is not respecting the .custom modalTransitionStyle I've set in the Segue. If I set that explicitly in prepareForSegue:, then it calls my delegate to get the UIPresentationController.

I have a custom Segue that is also a UIViewControllerTransitioningDelegate. In the perform() method, I set the destination transitioningDelegate to self:

self.destination.transitioningDelegate = self

and I either call super.perform() (if it’s a Present Modal or Present as Popover Segue), or self.source.present(self.destination, animated: true) (if it’s a Custom Segue, because calling super.perform() throws an exception).

The perform() and animationController(…) methods get called, but never presentationController(forPresented…).

Initially I tried making the Segue in the Storyboard "Present Modally" with my custom Segue class specified, but that kept removing the presenting view controller. I tried "Present as Popover," and I swear it worked once, in that it didn't remove the presenting view controller, but then on subsequent attempts it still did.

So I made it "Custom," and perform() is still being called with a _UIFullscreenPresentationController pre-set on the destination view controller, and my presentationController(forPresented…) method is never called.

Other solutions dealing with this issue always hinge on some mis-written signature for the method. This is mine, verbatim:

public func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController?

I've spent the last four days trying to figure out “proper” custom transitions, and it doesn't help that things don’t seem to behave as advertised. What am I missing?

Rick
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  • Hi Rick, I have a hard time figuring out, how your custom transition is going wrong. Can you maybe post the code for your custom transition or attach the link to a minimal test example? Also I assume you are using two standard ViewControllers, no NavigationController involved. Am I correct? – gebirgsbärbel Nov 13 '18 at 12:31
  • The presenting view controller is inside a UINavigationController (it’s the only one). I can’t post the code at the moment but will later today. – Rick Nov 13 '18 at 12:32
  • After reading your question again, I assume, that you want to have a drawer that overlays your current view, similar to the one in Apple Maps. As far as I know, you should not do this using to view controllers, as on iOS only one ViewController can be shown at the same time, but use a UIView instead. – gebirgsbärbel Nov 13 '18 at 12:36
  • I don’t think that’s true. You can have split view controllers on iPhone, and I’ve seen an example in a WWDC video where they make a popover on iPhone. – Rick Nov 13 '18 at 12:38
  • Hm, I would have to recheck, but if using a UIView instead of a separate ViewController also would be fine for you, here is an excellent tutorial, that shows how to implement drawers on iOS: https://www.raywenderlich.com/299-how-to-create-your-own-slide-out-navigation-panel-in-swift – gebirgsbärbel Nov 13 '18 at 12:40
  • I really want to use a custom UIViewController; there's some logic in this that I don't want polluting my main view controller. I'm noticing that iOS is not respecting my segue’s specified presentation style (It should be Custom, but in -prepareForSegue: it's UIModalPresentationFullScreen). – Rick Nov 14 '18 at 00:10
  • I've edited the question to show that it seems to be a bug in iOS. Figures. – Rick Nov 14 '18 at 00:26
  • I have created an answer, that should achieve the same effect (2 UIViewControllers on one screen, which can be animated like a drawer), but without a custom segue. Maybe this would be a good solution for you :) – gebirgsbärbel Nov 14 '18 at 11:10

1 Answers1

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Instead of using a custom presentation segue, you could use a Container View for your drawer. This way, you can use a UIViewController for your Drawer content, while avoiding the issue with the custom segue.

You achieve this in two steps: First pull a Container View into your main view controller and layout it properly. The storyboard would look like this: (You can see you have two view controllers. One for the main view and one for the drawer)

enter image description here

Second, you create an action that animates the drawer in and out as needed. One simple example could look like this:

@IBAction func toggleDrawer(_ sender: Any) {
    let newHeight: CGFloat
    if drawerHeightConstraint.constant > 0 {
        newHeight = 0
    } else {
        newHeight = 200
    }

    UIView.animate(withDuration: 1) {
        self.drawerHeightConstraint.constant = newHeight
        self.view.layoutIfNeeded()
    }
}

Here, I simply change the height constraint of the drawer, to slide it in and out. Of course you could do something more fancy :)

You can find a demo project here.

gebirgsbärbel
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