Windows Phone 8.1 Backgroundtask中的位置触发器不会触发

Question

我正在使用Windows Phone 8.1 [RT]应用程序，因为我在后台有更新位置，我正在使用GeofenceMonitor

 GeofenceMonitor gm = GeofenceMonitor.Current;
  gm.Geofences.Clear();
  Geoposition geoposition = await new Geolocator().GetGeopositionAsync();
  Geofence gf = new Geofence("InitalLocation", new Geocircle(geoposition.Coordinate.Point.Position, 1), MonitoredGeofenceStates.Entered | MonitoredGeofenceStates.Exited, false,TimeSpan.FromSeconds(5));
  gm.Geofences.Add(gf);

并为位置触发添加Backgroud任务

        var backgroundAccessStatus = await BackgroundExecutionManager.RequestAccessAsync();
        var geofenceTaskBuilder = new BackgroundTaskBuilder
        {
            Name = "GeofenceBackgroundTask",
            TaskEntryPoint = "BackgroundTask.GeofenceBackgroundTask"
        };

        var trigger = new LocationTrigger(LocationTriggerType.Geofence);
        geofenceTaskBuilder.SetTrigger(trigger);
        var geofenceTask = geofenceTaskBuilder.Register();

我不知道我错在哪里，但当我在1米无线电中的位置时，后台任务不会触发。

找到参考代码here