Windows 8后台任务

Question

So I seem to be having some issues making a background task fire in a windows store app; I have followed the white paper a tutorial and gone though the sample code from Microsoft and all iterations of my code seem to fail. Visual Studio does not give me any errors the background task just doesn't fire, the purpose of the task is to fire every 70 minutes when there is internet connectivity.

The scope of the code below is it's in own project called Tasks, and the manifest (not for this project but the main project in the solution) is properly filled for a background task to be found in this class

class BackroundBuilder
{
  public BackroundBuilder()
  {
    this.RegisterTimeTriggerBackgroundTask();
  }

  //this is the code that registers my backround task to run a trigger
  //was added for testing.
  private bool RegisterTimeTriggerBackgroundTask()
  {
    BackgroundTaskBuilder builder = new BackgroundTaskBuilder();
    builder.Name = "Background task test";
    builder.TaskEntryPoint = "PostPage.xmal";
    // Run every 70 minutes if the device has internet connectivity
    IBackgroundTrigger trigger = new TimeTrigger(70, false);
    builder.SetTrigger(trigger);
    IBackgroundCondition condition = new
        SystemCondition(SystemConditionType.InternetAvailable);

    //this is the trigger it's set to fire when internet becomes available            
    IBackgroundTrigger Itrigger = new
        SystemTrigger(SystemTriggerType.InternetAvailable,true);
    builder.SetTrigger(Itrigger);

    builder.AddCondition(condition);
    IBackgroundTaskRegistration task = builder.Register();

    return true;
  }

  public async void Run(IBackgroundTaskInstance taskInstance)
  {
    BackgroundTaskDeferral _deferral = taskInstance.GetDeferral();            

    //WindowsBlogReader.FeedDataSource updateAll = new WindowsBlogReader.FeedDataSource();
    //direct input for the test string is declared below but the updateAll declaration     
    // above is the one that will be used once the test works
    WindowsBlogReader.LiveTileTimeUpdate updateAll = new WindowsBlogReader.LiveTileTimeUpdae();

    //this is the test to see if the background task will fire
    //await was in front of the below statement but im injecting that String into a method
    //that is not setup for async the method being used once this works is an async 
    updateAll.update("Background task fired");
    //this update method adds a String too the list of Sting that's the live tile cycles though 
    _deferral.Complete();
  }     
}

this is the manifest xml code

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

Any help would be appreciated. If this code isn't enough information I can make more available. There are no (known) issues with other parts of the app as all the features work when the app is running.

Answer 1

您需要使BackroundBuilder类实现IBackgroundTask接口 。

Answer 2

Is this a typo: builder.TaskEntryPoint = "PostPage.xmal"; Should it be: builder.TaskEntryPoint = "PostPage.xaml"; ? I'd point the finger at that if SLaks' answer doesn't seem to fix the problem.

I'd type this as a comment but I don't have enough rep to do that.

Answer 3

TaskEntryPoint should be the name of your class (including namespace) which implements IBackgroundTask . Eg "BackgroundTasks.MyBackgroundTask".
This should also be added in your manifest file. Open Package.appxmanifest, go to the Declarations tab, add Background Tasks declaration and fill in the "Entry point" field with the same name (eg "BackgroundTasks.MyBackgroundTask").
Also, your task needs to be in a separate Windows Runtime Component project and every class in that project has to be public and sealed .

Here is a quick tutorial.
An extensive one can be found here .