Disable gesture to pull down form/page sheet modal presentation

In iOS 13 modal presentations using the form and page sheet style can be dismissed with a pan down gesture. This is problematic in one of my form sheets because the user draws into this box which interferes with the gesture. It pulls the screen down instead of drawing a vertical line.

How can you disable the vertical swipe to dismiss gesture in a modal view controller presented as a sheet?

Setting isModalInPresentation = true still allows the sheet to be pulled down, it just won't dismiss.

In general, you shouldn't try to disable the swipe to dismiss functionality, as users expect all form/page sheets to behave the same across all apps. Instead, you may want to consider using a full-screen presentation style. If you do want to use a sheet that can't be dismissed via swipe, set isModalInPresentation = true, but note this still allows the sheet to be pulled down vertically and it'll bounce back up upon releasing the touch. Check out the UIAdaptivePresentationControllerDelegate documentation to react when the user tries to dismiss it via swipe, among other actions.

If you have a scenario where your app's gesture or touch handling is impacted by the swipe to dismiss feature, I did receive some advice from an Apple engineer on how to fix that.

If you can prevent the system's pan gesture recognizer from beginning, this will prevent the gestural dismissal. A few ways to do this:

1. If your canvas drawing is done with a gesture recognizer, such as your own UIGestureRecognizer subclass, enter the began phase before the sheet’s dismiss gesture does. If you recognize as quickly as UIPanGestureRecognizer, you will win, and the sheet’s dismiss gesture will be subverted.

2. If your canvas drawing is done with a gesture recognizer, setup a dynamic failure requirement with -shouldBeRequiredToFailByGestureRecognizer: (or the related delegate method), where you return NO if the passed in gesture recognizer is a UIPanGestureRecognizer.

3. If your canvas drawing is done with manual touch handling (e.g. touchesBegan:), override -gestureRecognizerShouldBegin on your touch handling view, and return NO if the passed in gesture recognizer is a UIPanGestureRecognizer.

With my setup #3 proved to work very well. This allows the user to swipe down anywhere outside of the drawing canvas to dismiss (like the nav bar), while allowing the user to draw without moving the sheet, just as one would expect.

I cannot recommend trying to find the gesture to disable it, as it seems to be rather dynamic and can reenable itself when switching between different size classes for example, and this could change in future releases.

This gesture can be found in the modal view controller's presentedView property. As I debugged, the gestureRecognizers array of this property has only one item and printing it resulted in something like this:

> UIPanGestureRecognizer: 0x7fd3b8401aa0 > (_UISheetInteractionBackgroundDismissRecognizer);

So to disable this gesture you can do like below:

let vc = UIViewController()

self.present(vc, animated: true, completion: {
  vc.presentationController?.presentedView?.gestureRecognizers?[0].isEnabled = false
})

To re-enable it simply set isEnabled back to true:

vc.presentationController?.presentedView?.gestureRecognizers?[0].isEnabled = true

Note that iOS 13 is still in beta so a simpler approach might be added in an upcoming release.

Although this solution seems to work at the moment, I would not recommend it as it might not work in some situations or might be changed in future iOS releases and possibly affect your app.

Use this in the presented ViewController viewDidLoad:

if #available(iOS 13.0, *) {
    self.isModalInPresentation = true
}

In my case, I have a modal screen with a view that receives touches to capture customer signatures.

Disabling the gesture recognizer in the navigation controller solved the problem, preventing the modal interactive dismissal from being triggered at all.

The following methods are implemented in our modal view controller, and are called via delegate from our custom signature view.

Called from touchesBegan:

private func disableDismissalRecognizers() {
    navigationController?.presentationController?.presentedView?.gestureRecognizers?.forEach {
        $0.isEnabled = false
    }
}

Called from touchesEnded:

private func enableDismissalRecognizers() {
    navigationController?.presentationController?.presentedView?.gestureRecognizers?.forEach {
        $0.isEnabled = true
    }
}

Here is a GIF showing the behavior:

This question, flagged as duplicate, describes better the issue I had: https://stackoverflow.com/questions/58647239/disabling-interactive-dismissal-of-presented-view-controller-on-ios-13-when-drag

you can change the presentation style, if its in full screen the pull down to dismiss would be disabled

navigationCont.modalPresentationStyle = .fullScreen

No need to reinvent the wheel. It is as simple as adopting the UIAdaptivePresentationControllerDelegate protocol on your destinationViewController and then implement the relevant method:

func presentationControllerShouldDismiss(_ presentationController: UIPresentationController) -> Bool {
    return false
}

For example, let's suppose that your destinationViewController is prepared for segue like below:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "yourIdentifier",
       let destinationVC = segue.destination as? DetailViewController
    {
        //do other stuff

        destinationVC.presentationController?.delegate = destinationVC

    }
}

Then on the destinationVC (that should adopt the protocol described above), you can implement the described method func presentationControllerShouldDismiss(_ presentationController:) -> Bool or any of the other ones, in order to handle correctly your custom behaviour.

You can use the UIAdaptivePresentationControllerDelegate method presentationControllerDidAttemptToDismiss and disable the gestureRecognizer on the presentedView. Something like this:

func presentationControllerDidAttemptToDismiss(_ presentationController: UIPresentationController) {      
    presentationController.presentedView?.gestureRecognizers?.first?.isEnabled = false
}

For every body having problems with Jordans solution #3 running.

You have to look for the ROOT viewcontroller which is beeing presented, depending on your viewstack, this is maybe not you current view.

I had to look for my navigation controllers PresentationViewController.

BTW @Jordam: Thanks!

UIGestureRecognizer *gesture = [[self.navigationController.presentationController.presentedView gestureRecognizers] firstObject];
if ([gesture isKindOfClass:[UIPanGestureRecognizer class]]) {
    UIPanGestureRecognizer * pan = (UIPanGestureRecognizer *)gesture;
    pan.delegate = self;
}

You may first get a reference to the UIPanGestureRecognizer handling the page sheet dismissal in viewDidAppear() method. Notice that this reference is nil in viewWillAppear() or viewDidLoad(). Then you simply disable it.

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    presentationController?.presentedView?.gestureRecognizers?.first.isEnabled = false
}

If you want more customization rather than disabling it completely, for example, when using a navBar within the page sheet, set the delegate of that UIPanGestureRecognizer to your own view controller. That way, you can disable the gesture recognizer exclusively in your contentView while keeping it active in your navBar region by implementing

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {}

in IOS 13

if #available(iOS 13.0, *) {
    obj.isModalInPresentation = true
} else {
    // Fallback on earlier versions
}

Me, I use this :

-(void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];

for(UIGestureRecognizer *gr in self.presentationController.presentedView.gestureRecognizers) {
    if (@available(iOS 11.0, *)) {
        if([gr.name isEqualToString:@"_UISheetInteractionBackgroundDismissRecognizer"]) {
            gr.enabled = false;
        }
    }
}

Will try to describe method 2 already suggested by @Jordan H in more details:

1. To be able to catch and make decisions about the modal sheet's pan gesture add this into view controller's viewDidLoad:

   navigationController?.presentationController?.presentedView?.gestureRecognizers?.forEach { $0.delegate = self }

2. Enable the ability to catch the pan gesture together with your own gestures using gestureRecognizer(_:shouldRecognizeSimultaneouslyWith:)

3. The actual decision can go in gestureRecognizer(_:shouldBeRequiredToFailBy:)

Example code, which makes the swipe gesture to be preferred over sheet's pan gesture, if both present. It doesn't affect original pan gesture in areas where there is no swipe gesture recognizer and therefore the original "swipe to dismiss" can still work as designed.

extension PeopleViewController: UIGestureRecognizerDelegate {

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        if gestureRecognizer === UIPanGestureRecognizer.self && otherGestureRecognizer === UISwipeGestureRecognizer.self {
            return true
        }
        return false
    }

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return true
    }
}

In my case I have only a few swipe gesture recognizers, so comparing types is enough for me, but if there more of them it might make sense to compare the gestureRecognizers themselves (either programmatically added ones or as outlets from interface builder) as described in this doc: https://developer.apple.com/documentation/uikit/touches_presses_and_gestures/coordinating_multiple_gesture_recognizers/preferring_one_gesture_over_another

Here's how the code works in my case. Without it the swipe gesture was mostly ignored and worked only occasionally.

In the case when a UITableView or UICollectionView initiates the page sheet dismiss gesture when the user attempts to scroll past the top end of the scrolling view, this gesture can be disabled by adding an invisible UIRefreshControl that calls endRefreshing immediately.

See also https://stackoverflow.com/a/58676756/2419404

For navigation Controller, to avoid swipe interaction for presented view we can use:

if #available(iOS 13.0, *) {navController.isModalInPresentation = true}

In prepare(for:sender:) :

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == viewControllerSegueID {
        let controller = segue.destination as! YourViewController
        controller.modalPresentationStyle = .fullScreen
    }
}

or, after you initialize your controller:

let controller = YourViewController()
controller.modalPresentationStyle = .fullScreen