The URLSessionDownloadTask never starts the handle (_ backgroundTasks: Set <WKRefreshBackgroundTask>) for the WKURLSession in the background.

Question

The URLSessionDownloadTask never starts the handle (_ backgroundTasks: Set <WKRefreshBackgroundTask>) for the WKURLSession in the background.

Trying to understand why while scheduling a background URLSessionDownloadTask in WatchKit 3.0. func handle(_ backgroundTasks: Set<WKRefreshBackgroundTask>)

never works for WKURLSessionRefreshBackgroundTask

, but other tasks are executed as WKApplicationRefreshBackgroundTask

and WKSnapshotRefreshBackgroundTask

.

My code is in hours ExtensionDelegate

...

func applicationDidBecomeActive() {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.

    scheduleBackgroundRefresh(in: 10)
}

func handle(_ backgroundTasks: Set<WKRefreshBackgroundTask>) {
    // Sent when the system needs to launch the application in the background to process tasks. Tasks arrive in a set, so loop through and process each one.
    for task in backgroundTasks {
        // Use a switch statement to check the task type
        switch task {
        case let backgroundTask as WKApplicationRefreshBackgroundTask:
            // Be sure to complete the background task once you’re done.
            scheduleURLSession()
            backgroundTask.setTaskCompleted()
        case let snapshotTask as WKSnapshotRefreshBackgroundTask:
            // Snapshot tasks have a unique completion call, make sure to set your expiration date
            snapshotTask.setTaskCompleted(restoredDefaultState: true, estimatedSnapshotExpiration: Date.distantFuture, userInfo: nil)
        case let connectivityTask as WKWatchConnectivityRefreshBackgroundTask:
            // Be sure to complete the connectivity task once you’re done.
            connectivityTask.setTaskCompleted()
        case let urlSessionTask as WKURLSessionRefreshBackgroundTask: // This is never fired, Don't know why, arrrgggggg
            // Be sure to complete the URL session task once you’re done.

            let backgroundConfigObject = URLSessionConfiguration.background(withIdentifier: urlSessionTask.sessionIdentifier)
            let backgroundSession = URLSession(configuration: backgroundConfigObject, delegate: self, delegateQueue: nil) // delegate set to self here after rejoining the session

            print("Rejoining session ", backgroundSession)

            urlSessionTask.setTaskCompleted() // probably need to postpone this until the url `urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL)` has completed, but either way, this switch case is never met
        default:
            // make sure to complete unhandled task types
            task.setTaskCompleted()
        }
    }
}

func scheduleURLSession() {
    if let url = URL(string: "https://some.path.com") {
        let backgroundConfigObject = URLSessionConfiguration.background(withIdentifier: NSUUID().uuidString)
        let backgroundSession = URLSession(configuration: backgroundConfigObject, delegate: nil, delegateQueue: nil) // nil delegate here because delegate is "supposed" to be set in `handle(_ backgroundTasks:)` delegate method ("Rejoining session"). 

        let task = backgroundSession.downloadTask(with: url)
        task.resume()
    } else {
        print("Url error")
    }
}

func scheduleBackgroundRefresh(in seconds: TimeInterval) {
    let fireDate = Date(timeIntervalSinceNow: seconds)
    // optional, any SecureCoding compliant data can be passed here
    let userInfo = ["reason" : "background update"] as NSDictionary

    WKExtension.shared().scheduleBackgroundRefresh(withPreferredDate: fireDate, userInfo: userInfo) { (error) in
        if (error == nil) {
            print("successfully scheduled background task, use the crown to send the app to the background and wait for handle:BackgroundTasks to fire.")
        }
    }
}