自定义textfield,首次弹起emoji键盘

class EmojiTextField: UITextField {
    
    // required for iOS 13
    override var textInputContextIdentifier: String? { "" } // return non-nil to show the Emoji keyboard ¯\_(ツ)_/¯
    
    override var textInputMode: UITextInputMode? {
        for mode in UITextInputMode.activeInputModes {
            if mode.primaryLanguage == "emoji" {
                return mode
            }
        }
        return nil
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        commonInit()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        
        commonInit()
    }
    deinit {
        NotificationCenter.default.removeObserver(self, name: UITextInputMode.currentInputModeDidChangeNotification, object: nil)
    }
    func commonInit() {
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(inputModeDidChange),
                                               name: UITextInputMode.currentInputModeDidChangeNotification,
                                               object: nil)
    }
    
    @objc func inputModeDidChange(_ notification: Notification) {
        guard isFirstResponder else {
            return
        }
        
        if let currentInputMode = UITextInputMode.activeInputModes.first {
            if currentInputMode.primaryLanguage != "emoji" {
                return
            }
        }
        
        DispatchQueue.main.async { [weak self] in
            self?.reloadInputViews()
        }
    }
}