AppDelegate.swift中application部分:

private func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        self.window = UIWindow(frame: UIScreen.main.bounds)
        self.window?.backgroundColor = UIColor.white
        let navigationController = UINavigationController(rootViewController: ViewController())
        self.window?.rootViewController = navigationController
        self.window?.makeKeyAndVisible()
        
        return true
    }
 

ViewController.swift:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let screen = UIScreen.main.bounds
        
        self.navigationItem.title = "登入"
        
        /// 1.新增使用者ID：標籤
        let labelId = UILabel(frame: CGRect(x: 80,y: 115, width: 80, height: 21))
        labelId.text = "使用者ID："
        self.view.addSubview(labelId)
        
        /// 2.新增使用者ID TextField
        let textFieldId = UITextField(frame: CGRect(x: 170, y: 106, width: 100, height: 30))
        textFieldId.borderStyle = .roundedRect
        self.view.addSubview(textFieldId)
        
        /// 3.新增密碼：標籤
        let labelPwd = UILabel(frame: CGRect(x: 80, y: 178, width: 80, height: 21))
        labelPwd.text = "密碼："
        self.view.addSubview(labelPwd)
        
        /// 4.新增密碼 TextField
        let textFieldPwd = UITextField(frame: CGRect(x: 170, y: 169, width: 100, height: 30))
        textFieldPwd.borderStyle = .roundedRect
        self.view.addSubview(textFieldPwd)
        
        /// 5.新增 登入按鈕
        let buttonLogin = UIButton(type: .system)
        buttonLogin.frame = CGRect(x: (screen.size.width - 30)/2, y: 231, width: 50, height: 30)
        buttonLogin.setTitle("登入", for: UIControl.State())
        self.view.addSubview(buttonLogin)
        
        /// 6.新增 註冊按鈕
        let buttonReg = UIButton(type: .system)
        buttonReg.frame = CGRect(x: (screen.size.width - 30)/2, y: 294, width: 50, height: 30)
        buttonReg.setTitle("註冊", for: UIControl.State())
        buttonReg.addTarget(self, action: #selector(onClick(_:)), for: .touchUpInside)
        self.view.addSubview(buttonReg)
        
        NotificationCenter.default.addObserver(self, selector: #selector(registerCompletion(_:)), name: Notification.Name(rawValue: "RegisterCompletionNotification"), object: nil)
        
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        NotificationCenter.default.removeObserver(self)
    }
    

    
    @objc func onClick(_ sender: AnyObject){
        let registerViewController = RegisterViewController()
        
        //用於例項化導航控制器UINavigationController, 將RegisterViewController嵌入到導航控制器中.
        let navigationController = UINavigationController(rootViewController: registerViewController)
        //呈現模態檢視
        self.present(navigationController,animated: true,completion: nil)
    }
    
    @objc func registerCompletion(_ notionfication: Notification){
        let theData = notionfication.userInfo!
        let username = theData["username"] as! String
        print("username = " , username)
    }


}
 

RegisterViewController.swift:

import UIKit

class RegisterViewController: UIViewController {
    
    var txtUsername: UITextField!
    
    override func viewDidLoad() {
        super.viewDidLoad()

        self.navigationItem.title = "註冊"
        
        let saveButtonItem = UIBarButtonItem(barButtonSystemItem: .save, target: self, action: #selector(save(_:)))
        
        let cancelButtonItem = UIBarButtonItem(barButtonSystemItem: .cancel, target: self, action: #selector(cancel(_:)))
        
        self.navigationItem.rightBarButtonItem = saveButtonItem
        self.navigationItem.leftBarButtonItem = cancelButtonItem
        
        /// 1.新增使用者ID：標籤
        let labelId = UILabel(frame: CGRect(x: 35, y: 187, width: 100, height: 21))
        labelId.text = "使用者ID："
        self.view.addSubview(labelId)
        
        /// 2.新增Username TextField
        self.txtUsername = UITextField(frame: CGRect(x: 180, y: 178, width: 131, height: 30))
        self.txtUsername.borderStyle = .roundedRect
        self.view.addSubview(self.txtUsername)
    }
    

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    
    @objc func save(_ sender: AnyObject) {
        
        self.dismiss(animated: true) { () -> Void in
            NSLog("點選Save按鈕，關閉模態檢視")
            
            let dataDict = ["username" : self.txtUsername.text!]
            
            NotificationCenter.default.post(name: Notification.Name(rawValue: "RegisterCompletionNotification"), object: nil, userInfo: dataDict)
            
        }
    }
    
    @objc func cancel(_ sender: AnyObject) {
        self.dismiss(animated: true, completion: {
            NSLog("點選Cancel按鈕，關閉模態檢視")
        })
    }

}