UITabBarItem background set by UITabBar.appearance().selectionIndicatorImage misaligned on iPhone X

Question

The code:

let size = CGSize(width: tabBar.frame.width / CGFloat(TabBarItem.allValues.count),
                  height: tabBar.frame.height)
let image = UIImage.image(color: Color.action, size: size)
UITabBar.appearance().selectionIndicatorImage = image

On usual devices looks like this:

On iPhone X like this:

What can be the reason why iPhone X tab bar item background is misaligned?

---

UPDATE 1:

After changing code to be like below it looks better but it is still workaround as image not fully occupies tab bar item space:

  var image: UIImage
  if DeviceInfo.is5p8Inch {
     image = UIImage.image(color: Color.action, size: CGSize(width: 4, height: 4))
     image = image.resizableImage(withCapInsets: UIEdgeInsets(top: 2, left: 2, bottom: 2, right: 2), resizingMode: .tile)
  } else {
     let size = CGSize(width: tabBar.frame.width / CGFloat(TabBarItem.allValues.count),
                       height: tabBar.frame.height)
     image = UIImage.image(color: Color.action, size: size)
  }

---

UPDATE 2:

Code above called from viewDidLoad (also tries from viewWillAppear). Subclass of UITabBarController written 100% from code (no Storyboards/Xibs used).

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UPDATE 3:

We also have a custom button added as subview to UITabBar which positioned correctly. Only selectionIndicatorImage is misaligned...

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UPDATE 4:

Running original code above in viewDidAppear instead of in viewDidLoad or viewWillAppear produces following result:

Answer 1

You just need to call it after delay because it didn't get correct height of tabBar in your case and set it in self.tabBar, bellow code works for me i did it in viewDidload

Async.main {
        let size = CGSize(width: tabBar.frame.width / CGFloat(TabBarItem.allValues.count),
                          height: tabBar.frame.height)
        let image = UIImage.image(color: Color.action, size: size)
        UITabBar.appearance().selectionIndicatorImage = image
        self.tabBar.selectionIndicatorImage = image // this will change color and height of current tabBar
    }