Use this:

CGSize keyboardSize = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;

For Swift, you can use:

let keyboardSize = (notification.userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.size

Replace UIKeyboardFrameBeginUserInfoKey

with

UIKeyboardFrameEndUserInfoKey

The below is from Apple Docs.

UIKeyboardFrameBeginUserInfoKey- The key for an NSValue object containing a CGRect that identifies the start frame of the keyboard in screen coordinates.

UIKeyboardFrameEndUserInfoKey - The key for an NSValue object containing a CGRect that identifies the end frame of the keyboard in screen coordinates.

Try this:

Replace UIKeyboardFrameBeginUserInfoKey with UIKeyboardFrameEndUserInfoKey

I had a similar issue using Xcode Version 9.0 (9A235); although I was using Swift. In my keyboardWillShow method I wrote the following:

if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {


let heightValue = keyboardSize.height


...
}

Strangely, the first time keyboardWillShow was called, heightValue was 216.0, but during subsequent calls it had become 0! Perhaps this is an Xcode bug.

I replaced the UIKeyboardFrameBeginUserInfoKey with a UIKeyboardFrameEndUserInfoKey, and it fixed the issue for me.

This issue is happening on iOS 11.

Replace

"UIKeyboardFrameBeginUserInfoKey" with "UIKeyboardFrameEndUserInfoKey"

as shown below would fix the issue

Objective-C Code :

CGSize keyboardSize = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;

Swift 2.3 :

let keyboardSize = (NfnPsgVar.userInfo![UIKeyboardFrameEndUserInfoKey] as? NSValue)?.CGRectValue().size

Swift 3 :

let keyboardSize = (notification.userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.size

Your approach is trying to get the frame height before it is shown, and that is why it should be 0 which I am not sure why it is not at the first try! Here is an example of how to correctly get the keyboard height in swift 4.2:

func keyboardWillShow(notification: Notification) {


guard let userInfo = notification.userInfo else { return }


guard var keyboardFrame: CGRect = (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue else { return }


keyboardFrame = view.convert(keyboardFrame, from: nil)


let keyboardHeight = keyboardFrame.height
}

This will correctly provide the keyboard frame properties BEFORE keyboard appears.

Calculate keyboard height using the below code.

It is working for both devices with the safe area and non-safe area devices.

Code:

@objc func keyboardWillShow(notification: Notification) {
guard let keyboardFrame = notification.userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else {
return
}
let keyboardHeight: CGFloat
if #available(iOS 11.0, *) {
let window = UIApplication.shared.keyWindow
let bottomPadding = window?.safeAreaInsets.bottom ?? 0.0
keyboardHeight = keyboardFrame.cgRectValue.height - bottomPadding
} else {
keyboardHeight = keyboardFrame.cgRectValue.height
}
}

Eventhough we get accurate keyboard height when we adjust BottomSpace Constraints from SafeArea it makes more empty space. So we have to subtract safeArea margin from keyboard height if we are going to adjust the bottomSpace Constraints.

    @objc func keyBoardWillShow(notification: NSNotification) {
                  

    

if let keyboardFrame: NSValue = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue {
var bottomPadding: CGFloat = 0
//IF device is latest including iPhone x, it will have bottom padding as safeArea Insets. So we have to subtract that from REAL Keyboard HEIGHT.
if let window = UIApplication.shared.windows.first{
bottomPadding = window.safeAreaInsets.bottom
}
    

let keyboardRectangle = keyboardFrame.cgRectValue
let keyboardHeight = keyboardRectangle.height - bottomPadding
bottomSpaceConstraint.constant = keyboardHeight
}
self.view.layoutIfNeeded()
}