1.刪除StoryBoard，需要設置Main為空以及刪除plist文件中對應StoryBoard一欄，否則crash
2.按鈕添加點擊方法正確姿勢

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.red
        
        let btn = UIButton(type: UIButton.ButtonType.contactAdd)
        btn.center = CGPoint(x: 100, y: 100)
        btn.addTarget(self, action:#selector(btnClick), for: UIControl.Event.touchUpInside)
        view.addSubview(btn)
    }
    
    @objc func btnClick() {
        print("點擊了按鈕")
    }


}