UWP后台任务5次后没有运行

Question

我正在关注https://docs.microsoft.com/en-us/windows/uwp/launch-resume/create-and-register-a-background-task文档以创建一个后台任务,该任务将每15分钟运行一次并ping一项服务.

1. 使用实现IBackgroundTask的公共密封类创建了一个Windows运行时组件项目

   namespace PeriodicBackgroundTask
   {
       public sealed class FifteenMinutePeriodicTimer : IBackgroundTask
       {
           private static readonly FileLogWriter mWriteLogToFile = new FileLogWriter();
           public FifteenMinutePeriodicTimer() { }
   
           public void Run(IBackgroundTaskInstance taskInstance)
           {
               try
               {
                   taskInstance.Canceled += new BackgroundTaskCanceledEventHandler(OnCanceled);
                   mDeferral = taskInstance.GetDeferral();
                   mWriteLogToFile.log("Starting periodic timer at " + DateTime.Now.ToString());
   
                   // Calling method to do a Post call to a service.
   
                   mWriteLogToFile.log("Finishing periodic timer at " + DateTime.Now.ToString());
               }
               catch (Exception ex)
               {
                   mWriteLogToFile.log("Fifteen Minute periodic timer failed.", ex);
               }
               finally
               {
                   // Adding some buffer for async processes to finish.    
                   Task.Delay(TimeSpan.FromSeconds(15)).Wait();
                   mDeferral.Complete();
               }
           }
   
           private void OnCanceled(IBackgroundTaskInstance sender, BackgroundTaskCancellationReason reason)
           {
               mWriteLogToFile.log("Fifteen minute periodic timer is canceled. {0}", reason.ToString());
           }
       }
   }
   

2. 在UWP应用程序的Package.appmanifest文件中输入

   <Extension Category="windows.backgroundTasks" EntryPoint="PeriodicBackgroundTask.FifteenMinutePeriodicTimer">
     <BackgroundTasks>
       <Task Type="systemEvent" />
       <Task Type="timer" />
     </BackgroundTasks>
   </Extension>
   

3. 在App.xaml.cs中的OnLaunched方法的开头注册Timer

   public async static Task RegisterBackgroundTask()
   {
       foreach (var task in BackgroundTaskRegistration.AllTasks)
       {
           if (String.Equals(task.Value.Name, TASK_NAME))
           {
               mWriteLogToFile.log("Old version of fifteen minute periodic timer found. Unregistering it.");
               BackgroundExecutionManager.RemoveAccess();
               // Unregistering so that any update in Background task can be applied.
               task.Value.Unregister(true);
               break;
           }
       }
       BackgroundAccessStatus backgroundAccessStatus = await BackgroundExecutionManager.RequestAccessAsync();
       if (backgroundAccessStatus == BackgroundAccessStatus.DeniedByUser ||
       backgroundAccessStatus == BackgroundAccessStatus.DeniedBySystemPolicy)
       {
           mWriteLogToFile.log("Fifteen minute periodic timer registration failed, due to Request access status.");
           return;
       }
   
       BackgroundTaskBuilder builder = new BackgroundTaskBuilder();
       builder.Name = TASK_NAME;
       builder.TaskEntryPoint = "PeriodicBackgroundTask.FifteenMinutePeriodicTimer";
       builder.SetTrigger(new TimeTrigger(15, false));
       builder.CancelOnConditionLoss = false;
   
       var backgroundTask = builder.Register();
       if (backgroundTask != null)
       {
           mWriteLogToFile.log("Fifteen minute periodic timer registration SUCCESSFUL.");
       }
       else
       {
           mWriteLogToFile.log("Fifteen minute periodic timer registration FAILED.");
       }
   }
   

安装应用程序后,FifteenMinuteBackgroundTimer运行5或6次.有时5,有时6.当我尝试使用Visual Studio调试任务时,我可以调试它.我不确定,为什么FifteenMinuteBackgroundTimer在5次运行后死亡.请问有谁可以告诉我如何调试此问题？

更多信息:

Windows Build:1607
Microsoft.NETCore.UniversalWindowsPlatform:5.1.0

Answer 1

您很可能会遇到两项与电力相关的政策。

1. 周期性定时器触发被认为是机会性的。根据后台使用的能源量（未通电且屏幕关闭时），您的任务可能不会被触发，以便为其他关键用户活动（例如接收短信、推送或来电）节省能源。要验证这是否是您遇到的情况：您可以在“设置->系统->电池->应用程序电池”面板中将应用程序切换为“始终允许”。
2. 您还提到，如果屏幕关闭，当触发器运行时，网络将不起作用。在备用系统中，您需要将 IsNetworkRequested 指定为触发器注册的一部分，以便系统在任务期间将网络接口置于完全操作模式。请参阅此处的文档：https://learn.microsoft.com/en-us/uwp/api/Windows.ApplicationModel.Background.BackgroundTaskBuilder