UITabBar items jumping on back navigation on iOS 12.1

Question

I have an iOS app with UITabBarController on a master screen, navigating to a detail screen hiding the UITabBarController with setting hidesBottomBarWhenPushed = true.

When going back to the master screen the UITabBarController does a strange "jump" as shown on this GIF:

This happens only on iOS 12.1, not on 12.0 or 11.x.

Seems like an iOS 12.1 bug, because I noticed other apps like FB Messenger with this behavior, but I was wondering, is there some kind of workaround for it?

Answer 1

In your UITabBarController, set isTranslucent = false

Answer 2

Apple has now fixed that in iOS 12.1.1

Answer 3

I guess it's Apple's bug But you can try this as a hot fix: just create a class for your tabBar with following code:

import UIKit

class FixedTabBar: UITabBar {

    var itemFrames = [CGRect]()
    var tabBarItems = [UIView]()


    override func layoutSubviews() {
        super.layoutSubviews()

        if itemFrames.isEmpty, let UITabBarButtonClass = NSClassFromString("UITabBarButton") as? NSObject.Type {
            tabBarItems = subviews.filter({$0.isKind(of: UITabBarButtonClass)})
            tabBarItems.forEach({itemFrames.append($0.frame)})
        }

        if !itemFrames.isEmpty, !tabBarItems.isEmpty, itemFrames.count == items?.count {
            tabBarItems.enumerated().forEach({$0.element.frame = itemFrames[$0.offset]})
        }
    }
}

Answer 4

In my case (iOS 12.1.4), I found that this weird glitchy behaviour was triggered by modals being presented with the .modalPresentationStyle = .fullScreen

After updating their presentationStyle to .overFullScreen, the glitch went away.