keyboardWillShow Notification not called immediately after becomeFirstResponder - ios

Question

I have implemented keyboardWillShow: and keyboardWillHide: notifications. I am registering the notifications and they work perfectly after directly touching the screen on the UITextField, but there's a problem. In my viewDidLoad right after registering the notifications I'm calling becomeFirstResponder. The keyboard pops up but the keyboardWillShow: is not getting called (as mentioned, only the first time. It seems like there's a delay from the time you call the function to register the notification and the time it is actually registered, and I shouldn't delay the execution of becomeFirstResponder). Any ideas?
#objc func keyboardWillShow(_ notification: NSNotification) {
print("Show")
if let keyboardSize = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
var userInfo = notification.userInfo!
var keyboardFrame:CGRect = (userInfo[UIKeyboardFrameBeginUserInfoKey] as! NSValue).cgRectValue
keyboardFrame = self.view.convert(keyboardFrame, from: nil)
var contentInset: UIEdgeInsets = self.tv_main.contentInset
contentInset.bottom = keyboardSize.height
self.tv_main.contentInset = contentInset
let indexpath = IndexPath(row: 0, section: 0)
self.tv_main.scrollToRow(at: indexpath, at: UITableViewScrollPosition.top, animated: true)
}
}
#objc func keyboardWillHide(_ notification: NSNotification) {
print("Hide")
if let _ = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
let contentInset:UIEdgeInsets = UIEdgeInsets.zero
self.tv_main.contentInset = contentInset
}
}
override func viewDidLoad() {
super.viewDidLoad()
tv_main.delegate = self
tv_main.dataSource = self
tf_search.delegate = self
NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
self.tf_search.becomeFirstResponder()
if let placeholder = tf_search.placeholder {
tf_search.attributedPlaceholder = NSAttributedString(string:placeholder, attributes: [NSAttributedStringKey.foregroundColor: UIColor.white])
}
}

Answer 1

You should call becomeFirstResponder in viewWillAppear or viewDidAppear.