[iOS] Keyboard와 동일한 애니메이션 적용하기

Animate With The iOS Keyboard In Swift

 Keyboard가 보이고 사라질 때, NSNotificationd의 userInfo에 들어있는 필드들을 통해서 keyboard의 크기와 animation duration, curve정보까지 받아낼 수 있다.

 

import UIKit

class ViewController: UIViewController {
    
    @IBOutlet weak var textField: UITextField!
    @IBOutlet weak var labelTopMargin: NSLayoutConstraint!
    let defaultTopMargin: CGFloat = 500
    
    override func viewDidLoad() {
        super.viewDidLoad()
        labelTopMargin.constant = defaultTopMargin
        
        // Subscribe to Keyboard Will Show notifications
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(_:)), name: UIResponder.keyboardWillShowNotification, object: nil)

        // Subscribe to Keyboard Will Hide notifications
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(_:)), name: UIResponder.keyboardWillHideNotification, object: nil)
        
        self.view.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(hideKeyboard)))
    }
    
    @objc
    func hideKeyboard() {
        textField.resignFirstResponder()
    }
    
    @objc
    dynamic func keyboardWillShow(_ notification: NSNotification) {
        animateLabelWithKeyboard(notification: notification)
    }
        
    @objc
    dynamic func keyboardWillHide(_ notification: NSNotification) {
        animateLabelWithKeyboard(notification: notification)
    }
    
    func animateLabelWithKeyboard(notification: NSNotification) {
        animateWithKeyboard(notification: notification, animations: { keyboard in
            self.labelTopMargin.constant = self.defaultTopMargin - (UIScreen.main.bounds.height - keyboard.origin.y)
        })
    }
    
}
extension ViewController {
    func animateWithKeyboard(notification: NSNotification, animations: ((_ keyboardFrame: CGRect) -> Void)?) {
        // Extract the duration of the keyboard animation
        let durationKey = UIResponder.keyboardAnimationDurationUserInfoKey
        let duration = notification.userInfo![durationKey] as! Double
        
        // Extract the final frame of the keyboard
        let frameKey = UIResponder.keyboardFrameEndUserInfoKey
        let keyboardFrameValue = notification.userInfo![frameKey] as! NSValue
        
        // Extract the curve of the iOS keyboard animation
        let curveKey = UIResponder.keyboardAnimationCurveUserInfoKey
        let curveValue = notification.userInfo![curveKey] as! Int
        let curve = UIView.AnimationCurve(rawValue: curveValue)!

        // Create a property animator to manage the animation
        let animator = UIViewPropertyAnimator(
            duration: duration,
            curve: curve
        ) {
            // Perform the necessary animation layout updates
            animations?(keyboardFrameValue.cgRectValue)
            
            // Required to trigger NSLayoutConstraint changes
            // to animate
            self.view?.layoutIfNeeded()
        }
        
        // Start the animation
        animator.startAnimation()
    }
}

중앙의 label이 keyboard의 타이밍과 맞춰 함께 움직인다.