private func showCustomKeyboard() {
    textView.inputView = customKeyboardView
    textView.reloadInputViews()
}

private func showDefaultKeyboard() {
    textView.inputView = nil
    textView.reloadInputViews()
}

textView.inputView.resignFirstResponder()
textView.inputView.becomeFirstResponder()
textView.inputView = customKeyboardView
textView.reloadInputViews()

textView?.inputView.resignFirstResponder() // dismiss keyboard
textView?.inputView.becomeFirstResponder() // show keyboard
textView?.inputView = customKeyboardView // reassign new keyboard
textView?.reloadInputViews() // reload keyboard

textView?.inputView.resignFirstResponder() // dismiss keyboard
textView?.inputView = customKeyboardView // reassign new keyboard
textView?.reloadInputViews() // reload keyboard
textView?.inputView.becomeFirstResponder() // show keyboard