Swift keyboard frame change behavior controller

KeyboardBehaviorController.swift

//
//  KeyboardBehaviorController.swift
//  Spot
//
//  Created by Afshin on 6/20/17.
//  Copyright © 2017 AFE. All rights reserved.
//

import Foundation
import UIKit

class KeyboardBehaviorController {
    
    weak var appDelegate: AppDelegate?
    var closeBtn: UIButton?
    var closeBtn_constraints = [NSLayoutConstraint]()
    var isRegistered = false
    
    
    
    init(appDelegate: AppDelegate) {
        
        self.appDelegate = appDelegate
        registerKeyboardListener()
    }
    
    
    private func setupCloseBtn() {
        
        self.closeBtn = UIButton()
        self.closeBtn!.backgroundColor = UIColor(ARGB: 0x55000000)
        self.closeBtn!.layer.masksToBounds = true
        self.closeBtn!.layer.cornerRadius = 20
        self.closeBtn!.setImage(#imageLiteral(resourceName: "KeyboardClose").scale(toSize: CGSize(width: 30, height: 30))!, for: .normal)
        self.closeBtn!.contentMode = .center
        self.closeBtn!.addTarget(self, action: #selector(btnKeyboardCloseClicked), for: .touchUpInside)
    }
    
    
    func registerKeyboardListener() {
        
        
        if appDelegate?.window != nil && !isRegistered {
            
            setupCloseBtn()
            
            NotificationCenter.default.addObserver(self, selector: #selector(onKeyboardFrameWillChange(_:)), name: Notification.Name.UIKeyboardWillChangeFrame, object: nil)
            
        }
    }
    
    
    @objc private func onKeyboardFrameWillChange(_ notification : Notification) {
        
        let duration = notification.userInfo?["UIKeyboardAnimationDurationUserInfoKey"]
        let keyboardEndRect = notification.userInfo?["UIKeyboardFrameEndUserInfoKey"] as! CGRect
        let keyboardBeginRect = notification.userInfo?["UIKeyboardFrameBeginUserInfoKey"] as! CGRect
        let isLocalUser = (notification.userInfo?["UIKeyboardIsLocalUserInfoKey"] as! Int) > 0
        
        
        guard isLocalUser else { return }
        
        
        //Current responder
        var responder = UIResponder.currentFirst()
        //The viewcontroller that is shown modally or top most view controller of current navigation controller
        var topMostVc : UIViewController? = nil
        
        //Finds the view topMostVc
        while let next = responder?.next {
            
            if let next = next as? UIViewController , (next.parent == nil || next.parent is UINavigationController) {
                
                topMostVc = next
                break
            }
            
            responder = next
        }
        
        
        if let vc = topMostVc, vc is KeyboardChangeResponsive {
            
            
            
            let isClosed = (UIScreen.main.bounds.height <= keyboardEndRect.origin.y)
            let isOpening = !isClosed
            
            //Attaches the close button to view if not attached before
            if isOpening && self.closeBtn_constraints.count == 0 {
                
                vc.view.addSubview(self.closeBtn!)
                self.closeBtn?.isHidden = false
                self.closeBtn?.layer.opacity = 0
                
                vc.view.layoutIfNeeded()
                
                self.closeBtn?.translatesAutoresizingMaskIntoConstraints = false
                self.closeBtn_constraints = [
                    
                    self.closeBtn!.bottomAnchor.constraint(equalTo: vc.view.bottomAnchor, constant: -20),
                    self.closeBtn!.rightAnchor.constraint(equalTo: vc.view.rightAnchor, constant: -20),
                    self.closeBtn!.widthAnchor.constraint(equalToConstant: 40),
                    self.closeBtn!.heightAnchor.constraint(equalToConstant: 40)
                    
                ]
                
                NSLayoutConstraint.activate(self.closeBtn_constraints)

            }
            
            //Animates the view's height
            UIView.animate(withDuration: duration as! TimeInterval, animations: {
                
                if (vc as! KeyboardChangeResponsive).keyboardBehavior == .resize {
                    
                    vc.view.frame.size.height =  vc.view.frame.size.height + (keyboardEndRect.origin.y - keyboardBeginRect.origin.y)
                }
                
                vc.view.layoutIfNeeded()
                
            }) {
                
                c in
                
                self.animateCloseBtn(visibility: isClosed)
            }
            
        }
    }
    
    
    private func animateCloseBtn(visibility: Bool) {
        
        if visibility {
            
            UIView.animate(withDuration: 0.3, animations: {
                
                self.closeBtn!.layer.opacity = 0
            }){ c in
                
                //Removes the close button from view and make it ready for next attachment
                self.closeBtn_constraints.removeAll()
                self.closeBtn?.superview?.removeConstraints(self.closeBtn_constraints)
                self.closeBtn!.removeFromSuperview()
            }
        }
        else {
            
            
            UIView.animate(withDuration: 0.3, animations: {
                
                self.closeBtn!.layer.opacity = 1
            })
        }
    }
    
    
    @objc private func btnKeyboardCloseClicked() {
        
        appDelegate?.window?.endEditing(true)
    }
    
    
}