Reusable base view controller to extend

ScrollStackViewController.swift

// Use as you wish!

import UIKit
import SnapKit

class ScrollStackViewController: UIViewController {

    let scrollView = UIScrollView()
    let contentView = UIView()
    let stackView = UIStackView()

    private lazy var keyboardAvoiding = KeyboardAvoiding(scrollView: self.scrollView, rootView: self.view, dismissKeyboardOnTap: true)

    /// Override to set insets for the stackview
    var stackViewInset: UIEdgeInsets {
        return UIEdgeInsets(top: view.statusBarHeight() + 30, left: 30, bottom: 30, right: 30)
    }

    var avoidKeyboard: Bool {
        return true
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(scrollView)
        scrollView.snp.makeConstraints { make in
            make.edges.equalToSuperview()
        }

        scrollView.addSubview(contentView)
        contentView.snp.makeConstraints { make in
            make.edges.equalToSuperview()
            make.width.equalTo(view)
        }

        stackView.axis = .vertical
        stackView.alignment = .fill
        contentView.addSubview(stackView)
        stackView.snp.makeConstraints { make in
            make.top.equalToSuperview().offset(stackViewInset.top)
            make.left.equalToSuperview().offset(stackViewInset.left)
            make.right.equalToSuperview().offset(-stackViewInset.right)
            make.bottom.equalToSuperview().offset(-stackViewInset.bottom)
        }
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        if avoidKeyboard {
            keyboardAvoiding.activate()
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        if avoidKeyboard {
            keyboardAvoiding.deactivate()
        }
    }

    func wrapWithCenteringContainer(_ contentView: UIView) -> UIView {
        let container = UIView()
        container.addSubview(contentView)
        contentView.snp.makeConstraints { make in
            make.top.bottom.centerX.equalToSuperview()
            make.left.greaterThanOrEqualToSuperview()
            make.right.lessThanOrEqualToSuperview()
        }
        return container
    }
}

class KeyboardAvoiding {

    private let scrollView: UIScrollView
    private let rootView: UIView
    private let dismissKeyboardOnTap: Bool

    private var originalBottomInset: CGFloat?

    private lazy var tapGestureRecognizer: UITapGestureRecognizer = {
        let recognizer = UITapGestureRecognizer(target: self, action: #selector(dismissKeyboard))
        recognizer.cancelsTouchesInView = false
        return recognizer
    }()

    init(scrollView: UIScrollView, rootView: UIView, dismissKeyboardOnTap: Bool) {
        self.scrollView = scrollView
        self.rootView = rootView
        self.dismissKeyboardOnTap = dismissKeyboardOnTap
    }

    func activate() {
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: UIResponder.keyboardDidShowNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)

        if dismissKeyboardOnTap {
            rootView.addGestureRecognizer(tapGestureRecognizer)
        }
    }

    func deactivate() {
        NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardDidShowNotification, object: nil)
        NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillHideNotification, object: nil)
        rootView.removeGestureRecognizer(tapGestureRecognizer)
    }

    @objc
    private func dismissKeyboard() {
        rootView.endEditing(true)
    }

    @objc
    private func keyboardWillShow(_ notification: Notification) {
        guard let userInfo = notification.userInfo as? [String: AnyObject],
            let keyboardFrame = userInfo[UIResponder.keyboardFrameEndUserInfoKey]?.cgRectValue
            else { return }

        let convertedFrame = rootView.convert(keyboardFrame, from: nil)
        let keyboardInset = scrollView.frame.maxY - convertedFrame.origin.y

        var insets = scrollView.contentInset

        // Set only once
        if originalBottomInset == nil {
            originalBottomInset = insets.bottom
        }

        insets.bottom = (originalBottomInset ?? 0) + keyboardInset

        scrollView.contentInset = insets
        scrollView.scrollIndicatorInsets = insets
    }

    @objc
    private func keyboardWillHide(_ notification: Notification) {
        var insets = scrollView.contentInset
        insets.bottom = originalBottomInset ?? 0

        scrollView.contentInset = insets
        scrollView.scrollIndicatorInsets = insets
    }
}