Animate With The iOS Keyboard In Swift

This post presents an implementation of animations that animate alongside the iOS keyboard animation. Following the method in this post will allow your views to animate smoothly when the iOS keyboard shows and hides.

1. Subscribe To Keyboard Show And Hide Notifications
2. keyboardAnimationCurveUserInfoKey and UIViewPropertyAnimator
3. Animate With The iOS Keyboard
4. Example Keyboard Animation Implementation
5. Move View With iOS Keyboard Animation

Subscribe To Keyboard Show And Hide Notifications

The first step is to subscribe to the will show and will hide keyboard animations.

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 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
        )
    }

    @objc
    dynamic func keyboardWillShow(
       _ notification: NSNotification
    ) { }
    
    @objc
    dynamic func keyboardWillHide(
        _ notification: NSNotification
    ) { }
}

keyboardAnimationCurveUserInfoKey and UIViewPropertyAnimator

The next step is to create a function that wraps the iOS keyboard animation. The iOS keyboard animation uses a custom animation curve that is not publically accessible. To animate with the keyboard, extract the curve from the notification using the key UIResponder.keyboardAnimationCurveUserInfoKey and then use a UIViewPropertyAnimator to perform the animations.

In the following implementation, the animations block passed into animateWithKeyboard allows the caller to specify layout changes that should animate with the iOS keyboard animation. An example implementation is available at the end of this post.

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()
    }
}

Animate With The iOS Keyboard

That’s it! Using the animateWithKeyboard method allows custom animations to move with the iOS keyboard. For example, a UITextField may move up and down as the iOS keyboard shows and hides.

Example Keyboard Animation Implementation

// ...

    @objc
    dynamic func keyboardWillShow(
        _ notification: NSNotification
    ) {
        animateWithKeyboard(notification: notification) { 
            (keyboardFrame) in
            let constant = 20 + keyboardFrame.height
            self.textFieldTrailingConstraint?.constant = constant
        }
    }
    
    @objc
    dynamic func keyboardWillHide(
        _ notification: NSNotification
    ) {
        animateWithKeyboard(notification: notification) { 
            (keyboardFrame) in
            self.textFieldTrailingConstraint?.constant = 20
        }
    }

// ...

Move View With iOS Keyboard Animation