Overlay a view over whole screen, when using UITabBarController?

Question

I want to overlay a HUD-style transparent graphic over the entire screen in a UITabBarController setup. The button to do this is in the first tab\'s screen (FirstViewController)

Answer 1

I really liked what Chase Robert had written here, so I thought to provide the Swift 3. version as well:

    if let window = view.window {
        let subView = UIView(frame: window.frame)
        window.addSubview(subView)
    }

I added the condition as well, so you don't get a crash if there's no windows.