KeyboardLayoutConstraint.swift

// The MIT License (MIT)
//
// Copyright (c) 2015 James Tang (j@jamztang.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

import UIKit

#if !os(tvOS)
@available(tvOS, unavailable)
public class KeyboardLayoutConstraint: NSLayoutConstraint {
    
    private var offset: CGFloat = 0
    private var keyboardVisibleHeight: CGFloat = 0
    
    @available(tvOS, unavailable)
    override public func awakeFromNib() {
        super.awakeFromNib()
        
        offset = constant
        
        NotificationCenter.default.addObserver(self, selector: #selector(KeyboardLayoutConstraint.keyboardWillShowNotification(_:)), name: UIWindow.keyboardWillShowNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(KeyboardLayoutConstraint.keyboardWillHideNotification(_:)), name: UIWindow.keyboardWillHideNotification, object: nil)
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    // MARK: Notification
    
    @objc func keyboardWillShowNotification(_ notification: Notification) {
        if let userInfo = notification.userInfo {
            if let frameValue = userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue {
                let frame = frameValue.cgRectValue
                keyboardVisibleHeight = frame.size.height
            }
            
            self.updateConstant()
            switch (userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber, userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? NSNumber) {
            case let (.some(duration), .some(curve)):
                
                let options = UIView.AnimationOptions(rawValue: curve.uintValue)
                
                UIView.animate(
                    withDuration: TimeInterval(duration.doubleValue),
                    delay: 0,
                    options: options,
                    animations: {
                        UIApplication.shared.keyWindow?.layoutIfNeeded()
                        return
                    }, completion: { finished in
                    })
            default:
                
                break
            }
        }
    }
    
    @objc func keyboardWillHideNotification(_ notification: NSNotification) {
        keyboardVisibleHeight = 0
        self.updateConstant()
        
        if let userInfo = notification.userInfo {
            
            switch (userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber, userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? NSNumber) {
            case let (.some(duration), .some(curve)):
                
                let options = UIView.AnimationOptions(rawValue: curve.uintValue)
                
                UIView.animate(
                    withDuration: TimeInterval(duration.doubleValue),
                    delay: 0,
                    options: options,
                    animations: {
                        UIApplication.shared.keyWindow?.layoutIfNeeded()
                        return
                    }, completion: { finished in
                    })
            default:
                break
            }
        }
    }
    
    func updateConstant() {
        self.constant = offset + keyboardVisibleHeight
    }
    
}

#endif