danielpunkass · February 3, 2020 04:57 · Feb 3, 2020
diff --git a/UIView+RSKeyboardLayoutGuide.swift b/UIView+RSKeyboardLayoutGuide.swift
@@ -0,0 +1,104 @@
+//
+//  UIView+RSKeyboardLayoutGuide.swift
+//  RSTouchUIKit
+//
+//  Created by Daniel Jalkut on 12/23/18.
+//
+
+import UIKit
+
+// Extends UIView to expose a keyboardLayoutGuide property that can be used to tie a view controller's content
+// to so that it will automatically move out of the way when the keyboard appears.
+
+extension UIView {
+
+	func layoutGuide(withIdentifier identifier: String) -> UILayoutGuide? {
+		// Should only ever be one with a matching identifier
+		return self.layoutGuides.filter { $0.identifier == identifier }.first
+	}
+
+	@objc(rsKeyboardLayoutGuide)
+	public var keyboardLayoutGuide: UILayoutGuide {
+		get {
+
+			let keyboardGuideIdentifier = "com.red-sweater.layoutguide.keyboard"
+			if let existingGuide = self.layoutGuide(withIdentifier: keyboardGuideIdentifier) {
+				return existingGuide
+			}
+			else {
+				let newGuide = UILayoutGuide()
+				newGuide.identifier = keyboardGuideIdentifier
+
+				self.addLayoutGuide(newGuide)
+
+				let heightConstraint = newGuide.heightAnchor.constraint(equalToConstant: 0)
+				heightConstraint.isActive = true
+				newGuide.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
+
+				// Subscribe to notifications of keyboard size change, so we can adapt our
+				// guide to match.
+				NotificationCenter.default.addObserver(forName: UIResponder.keyboardWillChangeFrameNotification, object: nil, queue: nil) { [weak self] note in
+					guard
+						let existingSelf = self,
+						let noteInfo = note.userInfo,
+						let keyboardFrame = noteInfo[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect,
+						let superview = existingSelf.superview
+					else {
+						return
+					}
+
+					let keyboardFrameInSuperview = superview.convert(keyboardFrame, from: nil)
+					let ourFrameInSuperview = superview.convert(existingSelf.frame, from: existingSelf)
+
+					// Special case - if the keyboard is floating we disregard its height. I don't know how
+					// to strictly tell if it's floating but when it is floating it seems to represent sometimes
+					// as having a 0 width or awkward 36 height. Let's just assume a keyboard width less than
+					// half the main screen width is floating.
+					let screenWidth = UIScreen.main.bounds.size.width
+					let isFloatingKeyboard = keyboardFrameInSuperview.width < (screenWidth / 2)
+
+					// The height anchor constant should be our view's max Y minus the keyboad frame's
+					// min Y, which is effectively the top edge of the keyboard.
+					let newKeyboardHeight = isFloatingKeyboard ? 0 : max(0.0, ourFrameInSuperview.maxY - keyboardFrameInSuperview.minY)
+
+					// Animate if we have pertinent animation info
+					if let animationDuration = noteInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? TimeInterval {
+						let animationCurve: UIView.AnimationCurve
+						if
+							let curveValue = noteInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? Int,
+							let validCurve = UIView.AnimationCurve(rawValue: curveValue)
+						{
+							animationCurve = validCurve
+						}
+						else {
+							 animationCurve = .easeInOut
+						}
+
+						// Map from curve value to animation options
+						let animationOptions: UIView.AnimationOptions
+						switch animationCurve {
+						case .easeInOut:
+							animationOptions = .curveEaseInOut
+						case .easeIn:
+							animationOptions = .curveEaseIn
+						case .easeOut:
+							animationOptions = .curveEaseOut
+						case .linear:
+							animationOptions = .curveLinear
+						default:
+							animationOptions = .curveEaseInOut
+						}
+
+						UIView.animate(withDuration: animationDuration, delay: 0, options: animationOptions, animations: {
+							heightConstraint.constant = newKeyboardHeight
+						}, completion: nil)
+					}
+					else {
+						heightConstraint.constant = newKeyboardHeight
+					}
+				}
+				return newGuide
+			}
+		}
+	}
+}
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