KeyboardManager

KeyboardManager

public class KeyboardManager {
	
	public struct KeyboardChange {
		public let visibleHeight: CGFloat
		public let endFrame: CGRect
		public let animationDuration: TimeInterval
		public let animationOptions: UIViewAnimationOptions
	}
	
	public typealias KeyboardChangeClosure = (KeyboardChange)->Void
	public var keyboardChangeClosure: KeyboardChangeClosure?
	private var bottomConstraintsToBeManaged = [UIView: CGFloat]()
	private var bottomInsetsToBeManaged = [UIScrollView: CGFloat]()
	
	public init() {
		NotificationCenter.default.addObserver(
			self,
			selector: #selector(KeyboardManager.keyboardWillChangeFrameNotificationRecieved(notification:)),
			name: NSNotification.Name.UIKeyboardWillChangeFrame,
			object: nil)
		
	}
	
	deinit {
		NotificationCenter.default.removeObserver(self)
	}
	
	// MARK: - Public -
	
	public func setListener(keyboardChangeClosure: KeyboardChangeClosure) {
		self.keyboardChangeClosure = keyboardChangeClosure
	}
	
	public func manageBottomConstraint(for view: UIView) {
		let bottomConstraint = bottomConstraintFromView(view: view)
		bottomConstraintsToBeManaged[view] = bottomConstraint?.constant ?? 0
	}
	
	public func manageBottomInset(for scrollView: UIScrollView) {
		bottomConstraintsToBeManaged[scrollView] = scrollView.contentInset.bottom
	}
	
	// MARK: - Private -
	
	private func bottomConstraintFromView(view: UIView) -> NSLayoutConstraint? {
		return view.superview?.constraints.filter {
			($0.firstItem === view || $0.secondItem === view) &&
			($0.firstAttribute == .bottom || $0.secondAttribute == .bottom)
		}.first
	}
	
	// MARK: - NSNotification -
	
 	@objc func keyboardWillChangeFrameNotificationRecieved(notification: NSNotification) {
		if  let userInfo = notification.userInfo,
			let window = UIApplication.shared.keyWindow,
			let endFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue,
			let duration: TimeInterval = (userInfo[UIKeyboardAnimationDurationUserInfoKey] as? NSNumber as TimeInterval??) ?? 0,
			let animationCurveRawNSN = userInfo[UIKeyboardAnimationCurveUserInfoKey] as? NSNumber {
			
			let animationCurveRaw = animationCurveRawNSN.uintValue
			let animationCurve: UIViewAnimationOptions = UIViewAnimationOptions(rawValue: animationCurveRaw)
			let y = endFrame.origin.y == CGFloat.infinity ? 0 : endFrame.origin.y
			let height = endFrame.size.height == CGFloat.infinity ? 0 : endFrame.size.height
			let offset: CGFloat = y + height - window.frame.size.height
			let keyboardVisibleHeight = height - offset
			
			let keyboardChange = KeyboardChange(
				visibleHeight: keyboardVisibleHeight,
				endFrame: endFrame,
				animationDuration: duration,
				animationOptions: animationCurve)
			
			keyboardChangeClosure?(keyboardChange)
			
			UIView.animate(
				withDuration: keyboardChange.animationDuration,
				delay: 0,
				options: keyboardChange.animationOptions,
				animations: {
				
					for (view, bottom) in self.bottomConstraintsToBeManaged {
						let bottomConstraint = self.bottomConstraintFromView(view: view)
						bottomConstraint?.constant = bottom + keyboardChange.visibleHeight
					}
					
					for (scrollView, bottom) in self.bottomInsetsToBeManaged {
						var inset = scrollView.contentInset
						inset.bottom = bottom + keyboardChange.visibleHeight
						scrollView.contentInset = inset
					}
					
				}, completion: nil)
		}
	}
	
}