Xcode9学习笔记28

    override func viewDidLoad() {        super.viewDidLoad()        // Do any additional setup after loading the view, typically from a nib.        let rect = CGRect(x: 130, y: 100, width: 0, height: 0)        let uiSwitch = UISwitch(frame: rect)//初始化开关对象、指定位置和尺寸        uiSwitch.setOn(true, animated: true)//设置开关的默认状态为选中        //给开关对象添加状态变化事件        uiSwitch.addTarget(self, action: #selector(ViewController.switchChanged(_:)), for: UIControlEvents.valueChanged)        self.view.addSubview(uiSwitch)//将开光对象添加到当前视图控制器的根视图    }    @objc func switchChanged(_ uiSwitch: UISwitch) {        var message = "Turn on the switch"        if(!uiSwitch.isOn) {            message = "Turn off the switch"        }        let alert = UIAlertController(title: "Information", message: message, preferredStyle: UIAlertControllerStyle.alert)//创建一个信息显示窗口，并设置其显示的内容        //创建一个按钮，作为提示窗口中的“确定”按钮，点击关闭窗口        let action = UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil)        alert.addAction(action)//将按钮添加到提示窗口        self.present(alert, animated: true, completion: nil)//在当前视图控制器中，展示提示窗口    }