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August 14, 2019 06:20
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[KeyboardAvoiding] #protocol #iOS
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// | |
// KeyboardAvoiding.swift | |
// | |
// Created by Jay Lee on 08/14/2019. | |
// Copyright © 2019 Jay Lee <jaeho.lee@snu.ac.kr> | |
// This work is free. You can redistribute it and/or modify it under the | |
// terms of the Do What The Fuck You Want To Public License, Version 2, | |
// as published by Sam Hocevar. See http://www.wtfpl.net/ for more details. | |
// | |
import UIKit | |
protocol KeyboardAvoiding: UIViewController { | |
var keyboardAvoidingScrollView: UIScrollView { get } | |
var footerView: UIView? { get } | |
var activeField: UITextField? { get } | |
var activeFieldIsSubviewed: Bool { get } | |
var notificationCenter: NotificationCenter { get } | |
var keyboardObservers: [NSObjectProtocol] { get set } | |
} | |
extension KeyboardAvoiding { | |
var activeFieldIsSubviewed: Bool { return false } | |
var footerView: UIView? { return nil } | |
var notificationCenter: NotificationCenter { return .default } | |
func registerForKeyboardNotifications() { | |
keyboardObservers = [ | |
notificationCenter.addObserver( | |
forName: UIResponder.keyboardWillShowNotification, | |
object: nil, | |
queue: nil, | |
using: keyboardWillShow), | |
notificationCenter.addObserver( | |
forName: UIResponder.keyboardDidShowNotification, | |
object: nil, | |
queue: nil, | |
using: keyboardDidShow), | |
notificationCenter.addObserver( | |
forName: UIResponder.keyboardWillHideNotification, | |
object: nil, | |
queue: nil, | |
using: keyboardWillHide), | |
] | |
} | |
func unregisterForKeyboardNotifications() { | |
keyboardObservers.forEach { notificationCenter.removeObserver($0) } | |
} | |
func keyboardWillShow(_ notification: Notification) { | |
guard | |
let userInfo = notification.userInfo as NSDictionary?, | |
let value = userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue | |
else { return } | |
let keyboardHeight = value.cgRectValue.size.height | |
let contentInset = UIEdgeInsets( | |
top: 0, | |
left: 0, | |
bottom: keyboardHeight - (footerView?.frame.height ?? 0), | |
right: 0) | |
keyboardAvoidingScrollView.contentInset = contentInset | |
keyboardAvoidingScrollView.scrollIndicatorInsets = contentInset | |
} | |
func keyboardDidShow(_ notification: Notification) { | |
guard | |
let userInfo = notification.userInfo as NSDictionary?, | |
let value = userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue, | |
let activeField = activeField | |
else { return } | |
let keyboardHeight = value.cgRectValue.size.height | |
// If active text field is hidden by keyboard, scroll it so it's visible | |
var frame = view.frame | |
frame.size.height -= keyboardHeight - (footerView?.frame.height ?? 0) | |
let activeFieldOrigin: CGPoint | |
// If activeField is not a direct subview of the `view`, convert the | |
// `frame.origin` with respect to the `view` | |
if activeFieldIsSubviewed { | |
activeFieldOrigin = activeField.superview? | |
.convert(activeField.frame.origin, to: view) ?? activeField.frame.origin | |
} else { | |
activeFieldOrigin = activeField | |
.convert(activeField.frame.origin, to: view) | |
} | |
if !frame.contains(activeFieldOrigin) { | |
keyboardAvoidingScrollView | |
.scrollRectToVisible(activeField.frame, animated: true) | |
} | |
} | |
func keyboardWillHide(_ notification: Notification) { | |
keyboardAvoidingScrollView.contentInset = UIEdgeInsets.zero | |
keyboardAvoidingScrollView.scrollIndicatorInsets = UIEdgeInsets.zero | |
} | |
} |
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