Keyboard aware ViewController based on safeArea

KeyboardAwareVC.swift

import UIKit
import ObjectiveC

private var originalAdditionalSafeAreaInsetsKey: Int = 0
open class KeyboardAwareViewController: UIViewController {
    
    open class var backgroundTapEditingEndHandlerEnabled: Bool { true }
    
    private var originalAdditionalSafeAreaInsets: UIEdgeInsets? {
        get {
            objc_getAssociatedObject(self, &originalAdditionalSafeAreaInsetsKey) as? UIEdgeInsets
        }
        set {
            objc_setAssociatedObject(self, &originalAdditionalSafeAreaInsetsKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_COPY_NONATOMIC)
        }
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    override open func viewDidLoad() {
        dispatchPrecondition(condition: .onQueue(.main))
        super.viewDidLoad()
        setupKeyboardHandlers()
        guard Self.backgroundTapEditingEndHandlerEnabled else { return }
        setupBackgroundTapEditingEndHandler()
    }
    
    public func setupBackgroundTapEditingEndHandler() {
        let backgroundTapGesture = UITapGestureRecognizer(target: self, action: #selector(backgroundTapEditingEndHandler))
        let backgroundTapGestureDelegate = BackgroundTapGestureDelegate(backgroundTapGesture: backgroundTapGesture)
        backgroundTapGesture.delegate = backgroundTapGestureDelegate
        objc_setAssociatedObject(self, &backgroundTapGestureDelegateKey, backgroundTapGestureDelegate, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        view.addGestureRecognizer(backgroundTapGesture)
    }
    
    private func setupKeyboardHandlers() {
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(keyboardShow(notification:)),
                                               name: UIResponder.keyboardWillShowNotification, object: nil)
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(keyboardHide(notification:)),
                                               name: UIResponder.keyboardWillHideNotification, object: nil)
    }
    
    @objc private func keyboardShow(notification: NSNotification) {
        dispatchPrecondition(condition: .onQueue(.main))
        guard let notificationInfo = notification.userInfo else { return }
        let keyboardInitialFrame = notificationInfo[UIResponder.keyboardFrameBeginUserInfoKey].flatMap { ($0 as? NSValue)?.cgRectValue } ?? .zero
        let keyboardFinalFrame = notificationInfo[UIResponder.keyboardFrameEndUserInfoKey].flatMap { ($0 as? NSValue)?.cgRectValue } ?? .zero
        guard keyboardFinalFrame != keyboardInitialFrame else { return }
        let animationDuration = notificationInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double ?? 0.25
        let animationOptions = UIView.AnimationOptions(rawValue: notificationInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? UInt ?? UInt(UIView.AnimationCurve.easeInOut.rawValue))
        if let originalAdditionalSafeAreaInsets = originalAdditionalSafeAreaInsets {
            additionalSafeAreaInsets = originalAdditionalSafeAreaInsets
        } else {
            originalAdditionalSafeAreaInsets = additionalSafeAreaInsets
        }
        let overlappingKeyboardHeight: CGFloat
        if let window = view.window {
            overlappingKeyboardHeight = max(view.bounds.height - window.convert(keyboardFinalFrame, to: view).minY - view.safeAreaInsets.bottom, 0)
        } else {
            overlappingKeyboardHeight = max(keyboardFinalFrame.height - view.safeAreaInsets.bottom, 0)
        }
        additionalSafeAreaInsets = .init(top: 0, left: 0, bottom: overlappingKeyboardHeight + additionalSafeAreaInsets.bottom, right: 0)
        view.setNeedsLayout()
        viewSafeAreaInsetsDidChange()
        UIView.animate(
            withDuration: animationDuration,
            delay: 0,
            options: animationOptions,
            animations: {
                self.view.layoutIfNeeded()
            }
        )
    }
    
    @objc private func keyboardHide(notification: NSNotification) {
        dispatchPrecondition(condition: .onQueue(.main))
        guard let notificationInfo = notification.userInfo else { return }
        let keyboardInitialFrame = notificationInfo[UIResponder.keyboardFrameBeginUserInfoKey].flatMap { ($0 as? NSValue)?.cgRectValue } ?? .zero
        let keyboardFinalFrame = notificationInfo[UIResponder.keyboardFrameEndUserInfoKey].flatMap { ($0 as? NSValue)?.cgRectValue } ?? .zero
        guard keyboardFinalFrame != keyboardInitialFrame else { return }
        let animationDuration = notificationInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double ?? 0.25
        let animationOptions = UIView.AnimationOptions(rawValue: notificationInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? UInt ?? UInt(UIView.AnimationCurve.easeInOut.rawValue))
        additionalSafeAreaInsets = originalAdditionalSafeAreaInsets ?? .zero
        originalAdditionalSafeAreaInsets = nil
        view.setNeedsLayout()
        viewSafeAreaInsetsDidChange()
        UIView.animate(
            withDuration: animationDuration,
            delay: 0,
            options: animationOptions,
            animations: {
                self.view.layoutIfNeeded()
            }
        )
    }
    
    @objc private func backgroundTapEditingEndHandler() {
        dispatchPrecondition(condition: .onQueue(.main))
        view.endEditing(true)
    }
}

private var backgroundTapGestureDelegateKey: Int = 0
private final class BackgroundTapGestureDelegate: NSObject, UIGestureRecognizerDelegate {

    private weak var backgroundTapGesture: UIGestureRecognizer?

    fileprivate init(backgroundTapGesture: UIGestureRecognizer?) {
        self.backgroundTapGesture = backgroundTapGesture
    }

    fileprivate func gestureRecognizer(
        _ gestureRecognizer: UIGestureRecognizer,
        shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer
    ) -> Bool {
        guard gestureRecognizer === backgroundTapGesture else { return true }
        return false
    }
    
    fileprivate func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {
        return !(touch.view is UIControl)
    }
    
    fileprivate func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive press: UIPress) -> Bool {
        false
    }
}