I'm pretty much new to Xcode when trying to align a sheet to the safe area of iPhone X, it leaves a transparent area below the sheet.
Is there a way to set the fill of that area w/o expanding the sheet or align outside of the safe area?
Here is my tiny extension. If anybody can suggest an improvement to not access added view by "magic number" tag - welcome!
extension UIViewController {
private static let insetBackgroundViewTag = 98721 //Cool number
func paintSafeAreaBottomInset(withColor color: UIColor) {
    guard #available(iOS 11.0, *) else {
        return
    }
    if let insetView = view.viewWithTag(UIViewController.insetBackgroundViewTag) {
        insetView.backgroundColor = color
        return
    }
    let insetView = UIView(frame: .zero)
    insetView.tag = UIViewController.insetBackgroundViewTag
    insetView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(insetView)
    view.sendSubview(toBack: insetView)
    insetView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
    insetView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
    insetView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
    insetView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
    insetView.backgroundColor = color
}
}
Yes, it's not a good idea but can be a solution to your problem.
Follow this steps:
- Enable 'Safe Area Layout'
- Create/add a view (i.e. name it bottomPaddingView) (Programtically or using storyboard) with background color, same as your sheet color.
- Position it (using following constraints - following constraints are not a code structure, but just showing a constraint/anchor relationship)
 - bottomPaddingView.bottom = self.view.bottom
 - bottomPaddingView.trailing = self.view.trailing
 - bottomPaddingView.leading = self.view.leading
 - bottomPaddingView.top = self.view.safeAreaLayoutConstraint.bottom // If you've enabled 'Safe Area Layout'
 - or bottomPaddingView.top = self.view.bottomLayoutguide // If you've not enabled 'Safe Area Layout'
Now hide/unhide your bottomPaddingView with respect to actionship visibility with fade animation. 
来源:https://stackoverflow.com/questions/46881641/iphone-x-set-the-color-of-the-area-around-home-indicator
