Xcode9学习笔记30

    override func viewDidLoad() {        super.viewDidLoad()        // Do any additional setup after loading the view, typically from a nib.        let bt = UIButton(type: UIButtonType.system)        bt.frame = CGRect(x: 20, y: 120, width: 280, height: 44)        bt.setTitle("Question", for: UIControlState())        bt.addTarget(self, action: #selector(ViewController.showAlert), for: .touchUpInside)        bt.backgroundColor = UIColor.lightGray        self.view.addSubview(bt)    }        @objc func showAlert() {        let alert = UIAlertController(title: "Information", message: "Are you happy?", preferredStyle: UIAlertControllerStyle.alert)//初始化一个警告窗口，并设置窗口的标题文字和提示信息        let yes = UIAlertAction(title: "Yes", style: UIAlertActionStyle.default) { (alerts: UIAlertAction) in            print("Yes, I am happy.")        }        let no = UIAlertAction(title: "No", style: UIAlertActionStyle.default) { (alerts: UIAlertAction) in            print("No, I am not happy.")        }        alert.addAction(yes)        alert.addAction(no)        self.present(alert, animated: true, completion: nil)    }