Navbar not animating while hiding but still animates while reappearing

问题

I followed this answer and added a UIGestureRecognizer to show or hide the Navbar and Toolbar. Strangely, the Navbar is not silding while hiding but it still slides when it reappears. the toolbar is animating all the time.

I changed the code to:

override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
    print("got called")
    return UIStatusBarAnimation.slide
}

to see if it's being called when it hides and it is getting called. I also tried setting automaticallyAdjustsScrollViewInsets to false as suggested by the comments from the same answer but still no luck.

I can't find any information about this issue anywhere.

EDIT: here's my complete code:

override func viewDidLoad(){
    super.viewDidLoad()
    self.automaticallyAdjustsScrollViewInsets = false
    let gesture = UITapGestureRecognizer(target: self, action: #selector(toggle))
    view.isUserInteractionEnabled = true
    view.addGestureRecognizer(gesture)
}

func toggle() {
    navigationController?.setNavigationBarHidden(navigationController?.isNavigationBarHidden == false, animated: true)
    navigationController?.setToolbarHidden(navigationController?.isToolbarHidden == false, animated: true)
}
override var prefersStatusBarHidden: Bool {
    print("got called 1")
    return navigationController?.isNavigationBarHidden == true
}

override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
    print("got called 2")
    return UIStatusBarAnimation.slide
}

回答1:

The following Swift 4 code works fine with iOS 11 but does not work as expected for iOS 10. When using it with iOS 10, for some reason, the navigation bar does not animate when hiding and suddenly disappears.

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let gesture = UITapGestureRecognizer(target: self, action: #selector(toggle))
        view.addGestureRecognizer(gesture)
    }

    @objc func toggle() {
        navigationController?.setNavigationBarHidden(navigationController?.isNavigationBarHidden == false, animated: true)
    }

    override var prefersStatusBarHidden: Bool {
        return navigationController?.isNavigationBarHidden == true
    }

    override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
        return UIStatusBarAnimation.slide
    }

}

---

In order to fix this, you can use the following ViewController implementation that uses UIViewController's setNeedsStatusBarAppearanceUpdate() property:

class ViewController: UIViewController {

    override func viewDidLoad(){
        super.viewDidLoad()

        let gesture = UITapGestureRecognizer(target: self, action: #selector(toggle))
        view.addGestureRecognizer(gesture)
    }

    private var isHidden = false

    @objc func toggle() {
       navigationController!.setNavigationBarHidden(!isHidden, animated: true)
       isHidden = navigationController!.isNavigationBarHidden

        UIView.animate(withDuration: 0.3) {
            self.setNeedsStatusBarAppearanceUpdate()
        }
    }

    override var prefersStatusBarHidden: Bool {
        return isHidden
    }

    override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
        return UIStatusBarAnimation.slide
    }

}

---

As an alternative, you can also use the UIViewController implementation below:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad(){
        super.viewDidLoad()

        let gesture = UITapGestureRecognizer(target: self, action: #selector(toggle))
        view.addGestureRecognizer(gesture)
    }

    private var isHidden: Bool = false {
        willSet {
            self.navigationController!.setNavigationBarHidden(!self.isHidden, animated: true)
        }
        didSet {
            UIView.animate(withDuration: 0.3) {
                self.setNeedsStatusBarAppearanceUpdate()
            }
        }
    }

    @objc func toggle() {
        isHidden = !isHidden
    }

    override var prefersStatusBarHidden: Bool {
        return isHidden
    }

    override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
        return UIStatusBarAnimation.slide
    }

}

---

See this answer that shows up to 3 different ways to toggle both status bar and navigation bar for Swift 4 and iOS 11.

回答2:

Try this:

class ViewController: UIViewController {
     var isHidden:Bool = false
     @IBAction func clicked(sender: AnyObject) {
         isHidden = !isHidden
         UIView.animateWithDuration(0.5) { () -> Void in
             self.setNeedsStatusBarAppearanceUpdate()
         }
     }
     override func preferredStatusBarUpdateAnimation() -> UIStatusBarAnimation {
         return UIStatusBarAnimation.Slide
     }
     override func prefersStatusBarHidden() -> Bool {
         return isHidden
     }
   }

回答3:

The problem is that in iOS 11 navigationController?.isNavigationBarHidden always returns false. In iOS 10 this code works correct. I've not found the workaround yet (((

来源：https://stackoverflow.com/questions/45045885/navbar-not-animating-while-hiding-but-still-animates-while-reappearing