ActivityIndi cator（微调器）获取错误在解开Optional值时意外发现nil

Question

在我的共享类中，我编写微调器代码，它工作正常，但有时它会出错。

Error: Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

我在共享类中的代码：

import UIKit

class SharedClass: NSObject {

static let sharedInstance = SharedClass()

var transparentView:UIView!
var spinner = UIActivityIndicatorView()


//Show activity indicator
func activityIndicator(view:UIView) {

    DispatchQueue.main.async {
        let window = UIApplication.shared.keyWindow! //Error : Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
        self.transparentView = UIView()
        self.transparentView.frame = CGRect(x: 0, y: 0, width: window.frame.width, height: window.frame.height)
        self.transparentView.backgroundColor = UIColor.black.withAlphaComponent(0.4)
        window.addSubview(self.transparentView)

        if UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.pad {
            self.spinner = UIActivityIndicatorView(style: .whiteLarge)
            self.spinner.frame = CGRect(x: 0, y: 0, width: 60, height: 60)
        } else {
            self.spinner = UIActivityIndicatorView(style: .white)
            self.spinner.frame = CGRect(x: 0, y: 0, width: 40, height: 40)
        }
        self.spinner.center = view.center
        self.transparentView.addSubview(self.spinner)
        self.spinner.startAnimating()

        DispatchQueue.main.asyncAfter(deadline: .now() + 600.0) {//Stop spinner after 10 Sec's
            self.stopActivityIndicator()
            //self.transparentView.removeFromSuperview()
        }
    }
}

//Stop activity indicator
func stopActivityIndicator() {
    DispatchQueue.main.async {
        self.spinner.stopAnimating()
        self.spinner.removeFromSuperview()
        self.transparentView.removeFromSuperview()
    }
}

//Present alert on top of all windows
func alertWindow(title: String, message: String) {
    //Calling
    //SharedClass.sharedInstance.alertWindow(title:"", message:"")
    DispatchQueue.main.async(execute: {
        let alertWindow = UIWindow(frame: UIScreen.main.bounds)
        alertWindow.rootViewController = UIViewController()
        alertWindow.windowLevel = UIWindow.Level.alert + 1

        let alert2 = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let defaultAction2 = UIAlertAction(title: "OK", style: .default, handler: { action in
        })
        alert2.addAction(defaultAction2)

        alertWindow.makeKeyAndVisible()

        alertWindow.rootViewController?.present(alert2, animated: true, completion: nil)
    })
}


 private override init() {

}

}

我这样打电话

SharedClass.sharedInstance.activityIndi​​cator（view：self.view）//播放微调器

SharedClass.sharedInstance.stopActivityIndi​​cator（）//停止微调器

这是我的登录Btn代码

@IBAction func onClickLoginBtn(_ sender: UIButton) {

    let networkReachability = Reachability.forInternetConnection()
    let networkStatus:Int = (networkReachability?.currentReachabilityStatus())!.rawValue
    print(networkStatus)
    if networkStatus == NotReachable.rawValue {
        let msg = SharedClass.sharedInstance.noNetMsg
        SharedClass.sharedInstance.alertWindow(title: "", message: msg)
    } else {

        SharedClass.sharedInstance.activityIndicator(view: self.view)//Play spinner
        let parameters = "imei=\(deviceID)&devid=\(deviceID)&ver=\(ver)"
        print("Parameters : \(parameters)")
        var request = URLRequest(url: URL(string: url)!)

        request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
        request.httpMethod = "POST"

        print("URL : \(request)")

        request.httpBody = parameters.data(using: .utf8)

        let task = URLSession.shared.dataTask(with: request) { data, response, error in guard let data = data, error == nil else { // check for fundamental networking error
            SharedClass.sharedInstance.stopActivityIndicator() //Stop spinner
            print("error=\(String(describing: error))")
            SharedClass.sharedInstance.alertWindow(title: "", message: "\(String(describing: error!.localizedDescription))")
            return
            }

            SharedClass.sharedInstance.stopActivityIndicator() //Stop spinner

            if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode == 500 {
                SharedClass.sharedInstance.alertWindow(title: "", message: "Server Error")
            } else if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 { // check for http errors
                print("statusCode should be 200, but is \(httpStatus.statusCode)")
                print("response = \(String(describing: response))")
            }

            do {
                let response = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String: AnyObject]
                print(response!)


                if status == "SUCCESS" {


                } else {
                    let message = res[0]["message"] as! String
                    //Call alert function
                    SharedClass.sharedInstance.alertWindow(title: "", message: message)
                }

            } catch let error as NSError {
                print(error)
                print(error.localizedDescription)
            }
        }

        task.resume()

    }

}

在这里，当我第一次点击登录btn它工作正常。但当我得到响应请求超时。

错误

错误域= NSURLErrorDomain代码= -1001“请求超时。” UserInfo = {NSUnderlyingError = 0x7f9eab767d60 {Error Domain = kCFErrorDomainCFNetwork Code = -1001“（null）”UserInfo = {_ kCFStreamErrorCodeKey = -2102，_kCFStreamErrorDomainKey = 4}}

将显示警报。在这种情况下，当我点击登录btn第二次现在应用程序崩溃与错误：Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value。

1）我的代码格式是否正确（表示函数调用和JSON邮政编码）

2）如何解决这个错误。

Answer 1

您可以确保获得keyWindow，就像您没有进入窗口一样，您将在哪里显示您的活动加载程序。

以下列方式进行

guard let window = UIApplication.shared.keyWindow else {
  return
}

这正是paulw11的建议