Adds a Block View as Window Subview

AddBlockViewAsWindowSubview.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    
    // MARK: - Handling Application Background State
    
    func applicationDidEnterBackground(_ application: UIApplication) {
        let blockView = BlockView()
        blockView.tag = 123
        window?.addSubview(blockView)
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
        let blockViewTag = 123
        let blockView = window?.viewWithTag(blockViewTag)
        blockView?.removeFromSuperview()
    }
}