Extension for SwiftUI that reports the current keyboard height to Views through an EnvironmentVariable (modify to report any other notification).

EnvironmentVariables.swift

//
//  EnvironmentVariables.swift
//  PlaylogR
//
//  Created by Cenk Bilgen on 2019-10-12.
//  Copyright © 2019 Cenk Bilgen. All rights reserved.
//

import SwiftUI
import UIKit

// Custom Environment Variables

// For example have a View's property bound to the current keyboard height like:
// @Environment(\.keyboardHeight) var keyboardHeight: CGFloat

// MARK: Add new properties to EnvironmentValues

extension EnvironmentValues {
  
  var keyboardHeight : CGFloat {
    get { EnvironmentObserver.shared.keyboardHeight }
  }
  
}

// MARK: Pass notifications from UIResponder (or wherever) to set properties in EnvironmentValues

class EnvironmentObserver {
  
  static let shared = EnvironmentObserver()
  
  var keyboardHeight: CGFloat = 0 {
    didSet { print("Keyboard height \(keyboardHeight)") }
  }
  
 init() {
   
    // MARK: Keyboard Events
    
    NotificationCenter.default.addObserver(forName: UIResponder.keyboardDidHideNotification, object: nil, queue: OperationQueue.main) { [weak self ] (notification) in
      self?.keyboardHeight = 0
    }
    
    let handler: (Notification) -> Void = { [weak self] notification in
    
        guard let userInfo = notification.userInfo else { return }
        guard let frame = userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect else { return }
        
        // From Apple docs:
        // The rectangle contained in the UIKeyboardFrameBeginUserInfoKey and UIKeyboardFrameEndUserInfoKey properties of the userInfo dictionary should be used only for the size information it contains. Do not use the origin of the rectangle (which is always {0.0, 0.0}) in rectangle-intersection operations. Because the keyboard is animated into position, the actual bounding rectangle of the keyboard changes over time.
        
        self?.keyboardHeight = frame.size.height
    }
    
    NotificationCenter.default.addObserver(forName: UIResponder.keyboardDidShowNotification, object: nil, queue: OperationQueue.main, using: handler)

    NotificationCenter.default.addObserver(forName: UIResponder.keyboardDidChangeFrameNotification, object: nil, queue: OperationQueue.main, using: handler)
    
  }
  
}