在httpPost之后，PushViewController不起作用

Question

我制作了一个登录屏幕，该屏幕接受输入并与REST API通信以验证用户。 如果响应为真，则我不登录用户。 我写了一个方法openViewControllerBasedOnIdentifier（id）来切换视图。

REST API会正确返回true和false。 推送控制器被调用，但视图不变。 如果我仅在LoginAction方法'self.openViewControllerBasedOnIdentifier（“ PlayVC”）'中放置一行，并删除其余代码，该方法将正常工作。

这是我的代码@IBAction func LoginAction（_ sender：Any）{

    //self.openViewControllerBasedOnIdentifier("PlayVC")

Constants.login_status = false
    //created NSURL
    let requestURL = NSURL(string: URL_BK)

    //creating NSMutableURLRequest
    let request = NSMutableURLRequest(url: requestURL! as URL)

    //setting the method to post
    request.httpMethod = "POST"
    let username = phonenumber.text

    //creating the post parameter by concatenating the keys and values from text field
    let postParameters = "username="+username!+"&password=bk&schoolId=0";

    //adding the parameters to request body
    request.httpBody = postParameters.data(using: String.Encoding.utf8)


    //creating a task to send the post request
    let task = URLSession.shared.dataTask(with: request as URLRequest){
        data, response, error in
        let responseData = String(data: data!, encoding: String.Encoding.utf8)
        if error != nil{
            print("error is \(error)")
            return;
        }

        //parsing the response
        do {

            print(“Received data is ---%@",responseData as Any)

            let myJSON =  try JSONSerialization.jsonObject(with: data! , options: .allowFragments) as? NSDictionary


            if let parseJSON = myJSON {


                var status : Bool!

                status = parseJSON["status"] as! Bool?
                //print(status)

                if status==false
                {
                    Constants.login_status = false

                                        }
                else{
                    Constants.login_status = true
                    print("calling PLAYVC")

                    self.openViewControllerBasedOnIdentifier("PlayVC")


                }

            }
            else{
                print("NULL VALUE RECEIVED")
            }


        } catch {
            print(error)
        }

    }
    //executing the task
    task.resume()




}

Answer 1

您应该像这样在主线程上打开新的视图控制器：

DispatchQueue.main.async {
    self.openViewControllerBasedOnIdentifier("PlayVC")
}

当您调用URLSession.shared.dataTask时，您的REST API查询响应将在后台线程中处理，因此，当您调用任何UI动作时，都应按上述方式包装代码以在主线程中执行UI代码。 然后就可以了:)