UINavigationController向下滑动手势检测

Question

UINavigationController presented modally as form sheet can be swiped down to dismiss. This gesture is native in iOS and not mine. The problem is on iOS 13, it does not trigger viewWillAppear in the parent view controller after it gets dismissed. So I need a way to know the view controller is getting dismissed or got dismissed by a system gesture. How do I detect dismissal of view controller in that case?

Answer 1

Looks like UIAdaptivePresentationControllerDelegate might be what you're looking for, specifically the 4 new instance methods. Some more info here .

Answer 2

You can use func didMove(toParent parent: UIViewController?) ,this can detect the dismissal of view controller.There is just one thing, it works too when the current viewController appears. So you will need a variable to eliminate interference like this:

import UIKit

class ViewController: UIViewController {

    var isBack:Bool = false

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

    }

    override func didMove(toParent parent: UIViewController?) {
        super.didMove(toParent: parent)

        if isBack {
            //Dismiss.

        } else {
            isBack = true
        }
    }
}