如何解决快速从主线程访问布局引擎后,不得从后台线程对其进行修改
我在必要时给出了dispatchQueue.main.async {}
,但是当我在 dataTask 中给出断点时,它说
由于未捕获的异常“ NSInternalInconsistencyException”而终止应用程序,原因:“从主线程访问布局引擎后,不得从后台线程对其进行修改。”
class EventsViewController: UIViewController {
@IBOutlet weak var backBtn: UIButton!
var eventsListArray = [AnyObject]()
var eventType: String?
var eventList : EventsModel? = nil
@IBOutlet weak var eventsTableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
getAllEventsList()
}
func getAllEventsList() {
dispatchQueue.main.async {
let deviceid: String = (UIDevice.current.identifierForvendor?.uuidString)!
let personalId: String = UserDefaults.standard.string(forKey: "regUserID") ?? ""//KeychainWrapper.standard.string(forKey: "USERID") ?? ""
let headers = ["deviceid": deviceid,"userType": "personal","key": personalId]
dispatchQueue.main.async {
let string = Constants.GLOBAL_URL + "/get/allevents"
var urlComponents = URLComponents(string: string)
let eventStatus = self.eventType
let requestEventType = URLQueryItem(name: "eventstatus",value: eventStatus)
urlComponents?.queryItems = [requestEventType]
let urlStr = urlComponents?.url
let request = NSMutableuRLRequest(url: urlStr!,cachePolicy: .useProtocolCachePolicy,timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers as! [String : String]
let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest,completionHandler: { (data,response,error) -> Void in
if error == nil {
let httpResponse = response as? HTTPURLResponse
if httpResponse!.statusCode == 200 {
do {
let jsonObject = try JSONSerialization.jsonObject(with: data!,options: .mutableLeaves) as! [String :AnyObject]
print("publish event \(jsonObject)")
self.eventList = EventsModel.init(fromDictionary: jsonObject)
dispatchQueue.main.async {
if self.eventList?.events.count != 0 {
dispatchQueue.main.async {
self.eventsTableView.reloadData()
}
}
else {
dispatchQueue.main.async {
Constants.showAlertView(alertViewTitle: "",Message: "No Events \(self.eventType)",on: self)
self.eventList?.events.removeAll()
self.eventsTableView.reloadData()
}
}
}
} catch { print(error.localizedDescription) }
} else {
Constants.showAlertView(alertViewTitle: "",Message: "Something went wrong,Please try again",on: self)
}
}
})
dataTask.resume()
}
}
}
}
解决方法
您可能已经错过了一些在抛出错误时试图发出警报的地方。为什么您不立即在数据请求完成后立即进入主队列。
let dataTask = session.dataTask(with: request as URLRequest,completionHandler: { (data,response,error) -> Void in
DispatchQueue.main.async {
if error == nil {
//...
}
}
})
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