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);