将UITextView设置为焦点

func textViewShouldBeginEditing(_ textView: UITextView) -> Bool {
    return true
}

override func viewDidLoad() {
    super.viewDidLoad()
    textView.delegate = self
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    textView.becomeFirstResponder()
}