swift - 如果在 URLSession 之后呈现 View ，UIButton 标签会消失

Question

我正在制作一个社交应用程序，它通过 URLSession 检查用户是否登录。

所以我创建了 3 个 ViewController

1. 自定义启动屏幕VC
2. 登录VC
3. MainVc

CustomLaunchScreenVC:

View 出现后，我调用 checkIfSignedIn() 函数，该函数检查用户默认值中是否保存了 session 值。

如果NOT，则加载LoginVC

如果YES它调用另一个函数:loginWithSession(uid, session)

这个函数(loginWithSession)可能会因为里面有一个URLRequest而延迟。

它在网站上检查 session 是否有效，然后调用 goToMainVC() 或 goToLoginVC() 函数

<小时/>

现在的问题是，如果有一个已保存的 session ，但它无效，那么应用程序应该转到 SignInVC，它确实如此，但该 VC 上的按钮标签消失了，我不知道为什么.

(我尝试了一些方法，在从 loginWithSession() 函数中删除 URLSession Task 后，问题解决了，按钮也正常了。但我真的需要那个 URLSession 函数..)

所以可能是因为互联网连接造成了一些延迟，然后提交 VC 导致了类似的问题。

这是 CustomLaunchScreenVC 的代码(简化):

class CustomLaunchScreenVC : UIViewController {


    override func viewDidAppear(_ animated: Bool) {
        checkIfSignedIn()
    }

    func checkIfSignedIn(){
        let uid = defaults.integer(forKey: "uid")
        let session = defaults.string(forKey: "session")
        if uid != nil && session != nil {
            loginWithSession(session: session, uid: uid) { response in
                if let response = response {

                    if (response!.loggedIn == "yes"){
                        self.goToMainVC()
                    } else {
                        self.goToLoginVC() // This does NOT work, UIButtons' labels are NOT loading, and I don't know why :(
                    }
                }
            }
        } else {
            // there is no saved session so user is not logged in
            self.goToLoginVC() // This does works, UIButtons' labels are loading
        }
    }




    func loginWithSession(session: String, uid: Int, completion: @escaping (CustomTypeArray??)->()){

        let connectUrl = URL(string: "http://website.com/common/php/sessionLogin.php")
        var request = URLRequest(url: connectUrl!)
        request.httpMethod = "POST"
        let postString = "userId=\(uid)&session=\(session)"
        request.httpBody = postString.data(using: String.Encoding.utf8)

        let task = URLSession.shared.dataTask(with: request) {
            (data: Data?, response: URLResponse?, error: Error?) in

            //Simplified the code
            if (data.loggedin == "yes"){
                return completion(CustomTypeArray(loggedIn : "yes"))
            } else {
                return completion(CustomTypeArray(loggedIn : "no"))
            }
        }
        task.resume()

    }



    func goToLoginVC(){
        let loginVC = self.storyboard?.instantiateViewController(withIdentifier: "LoginVC") as! LoginVC
        self.present(loginVC, animated: false)
    }
    func goToMainVC(){
        let mainVC = self.storyboard?.instantiateViewController(withIdentifier: "MainVC") as! MainVC
        self.present(mainVC, animated: false)
    }
}

问题视频:Video

Answer 1

@rmaddy 帮助了我，谢谢!

解决方案是将所有 UI 代码移至主队列

DispatchQueue.main.async(execute: {() -> Void in
    self.goToSigninVC()
})