Display overlay view between ViewControllers - ios

Question

I am trying to display an overlay view on top of every ViewController after successfully logging in to show loading status of the app and load some data while this view is being displayed.
This view comes from a custom NIB file.
I display the OverlayLoadingView after a successful login request to the server, then I want to present a new ViewController on another Storyboard using:
self.present(vc, animated: true, completion: nil)
And finally hide the OverlayLoadingView in the next ViewController (This is why I handle it as a Singleton).
But when I present the next ViewController, the OverlayLoadingView disappears. Is there a way to display this loading view on top of everything while presenting a new view controller on the back at the same time?
Something like this:
LoginViewController -> Successfully logged in -> display OverlayView -> present MainViewController -> MainViewController presented below OverlayView -> Load initial data -> Hide OverlayView after initial data has been loaded.
#IBDesignable
public class OverlayLoadingView: UIView {
#IBOutlet weak var headerImageView: UIImageView!
#IBOutlet weak var detailTextLabel: UILabel!
class var sharedInstance: OverlayLoadingView {
struct Static {
static let instance: OverlayLoadingView = OverlayLoadingView(frame: UIScreen.main.bounds)
}
return Static.instance
}
// Custom view from the XIB file
fileprivate var view: UIView!
// Set header image directly by giving a value to headerImageURL variable from server response
/**
Initialiser method
*/
override init(frame: CGRect) {
super.init(frame: frame)
setupNib()
}
/**
Initialiser method
*/
required public init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
setupNib()
}
fileprivate func loadNib() -> UIView? {
return Bundle.main.loadNibNamed("OverlayLoadingView", owner: self, options: nil)?.first as? UIView
}
func setupNib() {
if let overlayLoadingView = loadNib() {
self.view = overlayLoadingView
let screenWidth = Util.screenSize().width
let screenHeight = Util.screenSize().height
self.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
view.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
self.addSubview(view)
}
}
public func showOverlay() {
if let appDelegate = UIApplication.shared.delegate as? AppDelegate,
let window = appDelegate.window {
self.alpha = 1.0
window.addSubview(self)
activityIndicator.startAnimating()
}
}
public func hideOverlayView() {
activityIndicator.stopAnimating()
self.removeFromSuperview()
}
}
EDIT:
To display the overlay view I am using:
DispatchQueue.main.async {
let storyboard = UIStoryboard(name: "TabMenu", bundle: nil)
let vc = storyboard.instantiateInitialViewController()!
OverlayLoadingView.sharedInstance.showOverlay()
self.present(vc, animated: true, completion: {
// Dismiss current VC?
})
}
The views hierarchy is shown like the following image. The overlay view should be over everything.

Answer 1

If your requirement is to display the loading view above all controllers you can add the view to the window.
if let window = UIApplication.shared.keyWindow {
let overlay = OverlayLoadingView(frame:UIScreen.main.bounds)
overlay.tag = 1001
window.addSubView(overlay)
// remove it like this
window.viewWithTag(overlay.tag)?.removeFromSuperView()
}
By the way this is not a Singleton as I'm able to use init and create another instance mark the init as private. Make the class final to avoid reflection and replace class with static As class can be overided but static can't.