在Swift 3.0中创建AppDelegate后，后退按钮消失

Question

我在xcode 8 swift 3.0中创建了以下结构。

在添加AppDelegate代码之前。 在应用，应用代表和配置文件控制器上，后退按钮仍然可以正常显示。

我使用segue打开页面。

但是，当我将AppDelegate代码添加到“主页”和“登录”控制器中后，“后退”按钮在“ 应用”，“代表代理和配置文件”控制器页面上消失了。

有人可以帮忙或解释为什么会这样吗？ 如何在申请，申请代表和个人资料页面上启用后退按钮？

谢谢。

迅捷

import UIKit
class ViewController: UIViewController {

    @IBOutlet var staffNumberLbl: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        staffNumberLbl.text = UserDefaults.standard.object(forKey: "login") as? String

    }
    override func viewDidAppear(_ animated: Bool) {
        let isUserLoggedIn = UserDefaults.standard.bool(forKey: "loggedIn")
        if(!isUserLoggedIn){
            self.performSegue(withIdentifier: "loginview", sender: self)
        }
    }

    @IBAction func logoutData(_ sender: Any) {
        UserDefaults.standard.set(false, forKey: "loggedIn")
        UserDefaults.standard.synchronize();
        let loginViewController = self.storyboard!.instantiateViewController(withIdentifier: "loginview") as! LoginViewController
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        appDelegate.window?.rootViewController = loginViewController
        appDelegate.window?.makeKeyAndVisible()
    }
}

Login.swift

import UIKit

class LoginViewController: UIViewController {
    @IBOutlet var loginlbl: UITextField!
    @IBOutlet var passlbl: UITextField!
    @IBOutlet var login_button: UIButton!

    var login: String!
    var pw: String!

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func loginData(_ sender: Any) {

        login = loginLbl.text
        pw = passLbl.text

        if(login == "" || pw == ""){
            return
        }
        else{
            let url     = URL(string: "http://localhost/login.php")
            let session = URLSession.shared
            let request = NSMutableURLRequest(url: url! as URL)
            request.httpMethod = "POST"

            let LoginDataToPost = "login=\(login!)&pw=\(pw!)"
            request.httpBody    = LoginDataToPost.data(using: String.Encoding.utf8)

            let task = session.dataTask(with: request as URLRequest, completionHandler: {
                (data, response, error) in
                if error != nil {
                    return
                }
                else {
                    do {
                        if let json = try JSONSerialization.jsonObject(with: data!) as? [String: String]
                        {
                            DispatchQueue.main.async
                                {
                                    let message = Int(json["message"]!)
                                    let login   = json["login"]

                                    if(message == 1) {
                                        UserDefaults.standard.set(true, forKey: "isUserLoggedIn")
                                        UserDefaults.standard.set(login, forKey: "login")
                                        UserDefaults.standard.synchronize();
                                        self.dismiss(animated: true, completion: nil)
                                        let myViewController:ViewController = self.storyboard!.instantiateViewController(withIdentifier: "ViewController") as! ViewController

                                        let appDelegate = UIApplication.shared.delegate as! AppDelegate
                                        appDelegate.window?.rootViewController = myViewController
                                        appDelegate.window?.makeKeyAndVisible()

                                        print("Value for login is : \(login!)")

                                        return
                                    }
                                    else {}
                            }  
                        }  
                        else {}
                    }
                    catch let jsonParse {}
                }
            })
            task.resume()
        }
    } 
}

AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?


    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.

        let mainStoryBoard: UIStoryboard = UIStoryboard(name: "Main", bundle:nil)

        let isUserLoggedIn:Bool = UserDefaults.standard.bool(forKey: "isUserLoggedIn")
        if(!isUserLoggedIn) {

            let loginViewController = mainStoryBoard.instantiateViewController(withIdentifier: "loginview") as! LoginViewController
            window!.rootViewController = loginViewController
            window!.makeKeyAndVisible()
        }
        else {
            let homePage = mainStoryBoard.instantiateViewController(withIdentifier: "ViewController") as! ViewController
            window!.rootViewController = homePage
            window!.makeKeyAndVisible()
        }
        return true
    }
}

Answer 1

您在设置rootviewcontroller时没有在logoutData和loginData函数中嵌入导航控制器。

使用此代码：

let navigationController = UINavigationController.init(rootViewController: myViewController)
appDelegate.window?.rootViewController = navigationController

在AppDelegate中使用以下代码：

if(!isUserLoggedIn) {

    let loginViewController = mainStoryBoard.instantiateViewController(withIdentifier: "loginview") as! LoginViewController
    let navigationController = UINavigationController.init(rootViewController: loginViewController)
    appDelegate.window?.rootViewController = navigationController
    window!.makeKeyAndVisible()
}
else {
     let homePage = mainStoryBoard.instantiateViewController(withIdentifier: "ViewController") as! ViewController
     let navigationController = UINavigationController.init(rootViewController: homePage)
     appDelegate.window?.rootViewController = navigationController
     window!.makeKeyAndVisible()
}

Answer 2

成功登录后，尝试使NavigationController成为rootViewController而不是您的ViewController

您的后退按钮将开始出现。

在AppDelegate中，在else块中，代替此行

让homePage = mainStoryBoard.instantiateViewController（withIdentifier：“ ViewController”）为！ ViewController

写这个

让homePage = mainStoryBoard.instantiateViewController（withIdentifier：“ NavigationController”）为！ UINavigationController

在LoginViewController内部，在块if（message == 1）中

更换

让myViewController：ViewController = self.storyboard！.instantiateViewController（withIdentifier：“ ViewController”）为！ ViewController

与

让navController：UINavigationController = self.storyboard！.instantiateViewController（withIdentifier：“ NavigationController”）为！ UINavigationController

还将故事板上的UINavigationController的故事板标识符设置为NavigationController

Answer 3

从Home.swift中删除它，

let appDelegate = UIApplication.shared.delegate as! AppDelegate
        appDelegate.window?.rootViewController = loginViewController
        appDelegate.window?.makeKeyAndVisible()

因为它不继承导航控制器的属性

并将其添加到Appdelegate.swift文件中

对于其他3个ViewController，您需要在eachSegway之间添加Navigation控制器，以便继承它或通过分别实例化ViewController来编码按钮

Answer 4

根据您的配置：

self.navigationItem.hidesBackButton = YES;

要么：

self.navigationController.navigationItem.hidesBackButton = YES;

或者，如果您只想禁用按钮而不隐藏它，则可以使用它。

self.navigationController.navigationItem.backBarButtonItem.enabled = NO;