Subview on top of window view in Swift

I want to place a UIView over the entire screen (including the navigation bar). This view will be black with 0.3 opacity. I want to do this to darken out the screen content and push a view on top of this. I am using this code:

UIApplication.sharedApplication().keyWindow?.addSubview(darkView)

This covers the whole screen as expected. However I now want to place another view on top of this dark view. Is there a way to do this? Everything I try just results in the view being under the dark view. Any pointers would be really appreciated! thanks

It's really simple.

You just add another view to window! And it will be there, on top of the first view you added. For example, this code adds a black view and a white view:

let window = UIApplication.sharedApplication().keyWindow!
let v = UIView(frame: window.bounds)
window.addSubview(v)
v.backgroundColor = UIColor.blackColor()
let v2 = UIView(frame: CGRect(x: 50, y: 50, width: 100, height: 50))
v2.backgroundColor = UIColor.whiteColor()
window.addSubview(v2)

You can also add the new view as a sub view of the first view you added:

let window = UIApplication.sharedApplication().keyWindow!
let v = UIView(frame: window.bounds)
window.addSubview(v)
v.backgroundColor = UIColor.blackColor()
let v2 = UIView(frame: CGRect(x: 50, y: 50, width: 100, height: 50))
v2.backgroundColor = UIColor.whiteColor()
v.addSubview(v2)

Swift 4

let window = UIApplication.shared.keyWindow!
let v = UIView(frame: window.bounds)
window.addSubview(v)
v.backgroundColor = .black
let v2 = UIView(frame: CGRect(x: 50, y: 50, width: 100, height: 50))
v2.backgroundColor = UIColor.white
v.addSubview(v2)

Simple!

For SWIFT 3 use this:

let window = UIApplication.shared.keyWindow!
window.addSubview(someView)

Swift 4, Adding a UIViewController as a subview to UIWindow

This code is for adding view controller as a subview, covering the whole window with simple animation.

let appDelegate = UIApplication.shared.delegate as! AppDelegate
var customReviewPopup = ReviewPopupViewController.init(nibName: "ReviewPopupViewController", bundle: Bundle.main)

self.appDelegate.window?.addSubview((customReviewPopup.view)!)
self.customReviewPopup.view.frame = (self.appDelegate.window?.bounds)!
self.customReviewPopup.view.alpha = 0
self.customReviewPopup.view.isHidden = true
    
UIView.animate(withDuration: 0.3, delay: 0, options: .transitionCrossDissolve, animations: {
    self.customReviewPopup.view.isHidden = false
    self.customReviewPopup.view.alpha = 1
}, completion: nil)
        

Swift 5:

let window = UIApplication.shared.windows.last!

let viewToShow = UIView(frame: CGRect(x: 0, y: 0, width: window.frame.size.width, height: 40.0))

viewToShow.backgroundColor = UIColor.white

window.addSubview(viewToShow)