Windows phone app 8.1 - Background Task is not launched

Question

Timer Background task in my windows phone 8.1 app was fired only when app was running in debug mode from visual studio. But if I launch even debug binary without debugging it doesn't work, not after 15 minutes, not after several hours. I tested it on windows phone 8.1 emulator and on nokia lumia 920 - the same result: in debug session it works (it is fired by system and I can fire it manually from Debug Location toolbar), but when app launched manually nothing happens.

I have windows store app also and time background task works in it quite well.

To use background tasks I did the following:

1. In my wp8.1 project's manifest I've added:

    <Extension Category="windows.backgroundTasks" EntryPoint="data.TimerHandler"> <BackgroundTasks> <Task Type="timer" /> </BackgroundTasks> </Extension> 

2. Created in namespace 'data' class MyTimerManager with such methods (among others):

    public static BackgroundTaskRegistration RegisterBackgroundTask(string taskEntryPoint, string taskName, IBackgroundTrigger trigger, IBackgroundCondition condition) { foreach (var cur in BackgroundTaskRegistration.AllTasks) { if (cur.Value.Name == taskName) return (BackgroundTaskRegistration)(cur.Value); } var builder = new BackgroundTaskBuilder(); builder.Name = taskName; builder.TaskEntryPoint = taskEntryPoint; builder.SetTrigger(trigger); if (condition != null) builder.AddCondition(condition); BackgroundTaskRegistration task = null; try { task = builder.Register(); } catch (Exception e) { LogError(e); } return task; } public static bool UnRegisterBackgroundTask(string taskName) { foreach (var cur in BackgroundTaskRegistration.AllTasks) { if (cur.Value.Name == taskName) { ((BackgroundTaskRegistration)cur.Value).Unregister(false); return true; } } return false; } public static void setupAlarm() { TimeTrigger timerTrigger = new TimeTrigger(30, false); string entryPoint = "data.TimerHandler"; string taskName = "TimerHandler task"; UnRegisterBackgroundTask(taskName);//just in case BackgroundTaskRegistration task = RegisterBackgroundTask(entryPoint, taskName, timerTrigger, null); Log("RegisterBackgroundTask: " + (task!=null ?task.Name:null)); } 

3. Created winrt component project, set its Default Namespace to 'data' (the same namespace that I used for class MyTimerManager in main app) added class TimerHandler:

    namespace data { public sealed class TimerHandler : IBackgroundTask { BackgroundTaskDeferral deferral = null; public async void Run(IBackgroundTaskInstance taskInstance) { deferral = taskInstance.GetDeferral(); await BackgroundExecutionManager.RequestAccessAsync(); await backgroundTimerCallAsync(); deferral.Complete(); } public static async Task backgroundTimerCallAsync() { NotificationSender ns = new NotificationSender(false, null, null); ns.sendNotification("Timer task msg");//my code which sends notification } } } 

4. Added reference to winrt component project into my wp8.1 project.

It is very important to use the same namespace: in my Windows Store 8.1 app background task wasn't fired until I realized that. And no a single word about it in MSFT docs!

Every app launch I call setupAlarm() and in log I see task's name (everything was fine). But nothing happens then. If I launch this task manually (from Lifecircle Events control) I see my notification. The strange thing that I rememeber month ago when this code was written I saw notifications. I've checked everything with msft docs, but everything seems fine. What else should I do to make tasks be fired?

Answer 1

In some examples I've found out that you should call RequestAccessAsync BEFORE registering your tasks! That did the trick.

Before means that you must wait until RequestAccessAsync finished, I had to call it in sync code, so I did it like that:

    BackgroundExecutionManager.RequestAccessAsync.AsTask().ContinueWith(
        (t) => registerMyTasks()).ConfigureAwait(false);