Question

我尝试在单一流程模型中使用新的＆＃;;背景活动＆＃39; API支持我的应用程序与后台任务。但是，我得到了，没有找到合适的方法来覆盖＆＃39;在＆＃39; OnBackgroundActivated＆＃39;方法。我的代码出了什么问题？

public MainPage()
    {
        this.InitializeComponent();
        Application.Current.EnteredBackground += Current_EnteredBackground;
    }

    private async void Current_EnteredBackground(object sender, Windows.ApplicationModel.EnteredBackgroundEventArgs e)
    {
        await RegisterBackgroundTask();
    }

    protected override void OnBackgroundActivated(BackgroundActivatedEventArgs args)
    {
        // show a toast
    }

    private void Page_Loaded(object sender, RoutedEventArgs e)
    {

    }

    private async Task RegisterBackgroundTask()
    {
        BackgroundAccessStatus backgroundAccessStatus = await BackgroundExecutionManager.RequestAccessAsync();

        if (backgroundAccessStatus == BackgroundAccessStatus.AllowedSubjectToSystemPolicy ||
            backgroundAccessStatus == BackgroundAccessStatus.AlwaysAllowed)
        {
            foreach (var bgTask in BackgroundTaskRegistration.AllTasks)
            {
                if (bgTask.Value.Name == "MyTask")
                {
                    bgTask.Value.Unregister(true);
                }
            }

            var builder = new BackgroundTaskBuilder();
            builder.Name = "MyTask";
            builder.SetTrigger(new TimeTrigger(15, false));

            // use builder.TaskEntryPoint if you want to not use the default OnBackgroundActivated
            // we’ll register it and now will start work based on the trigger, here we used a Time Trigger
            BackgroundTaskRegistration task = builder.Register();
        }
    }

Answer 1

此处的问题是您尝试覆盖OnBackgroundActivated课程中的MainPage方法。 MainPage类派生自Page Class，但Application.OnBackgroundActivated method是Application class的方法，Page类中不存在，因此您获得了no suitable method found to override错误。

要解决此问题，我们需要将OnBackgroundActivated方法放在App类中，如：

sealed partial class App : Application
{
    /// <summary>
    /// Override the Application.OnBackgroundActivated method to handle background activation in 
    /// the main process. This entry point is used when BackgroundTaskBuilder.TaskEntryPoint is 
    /// not set during background task registration.
    /// </summary>
    /// <param name="args"></param>
    protected override void OnBackgroundActivated(BackgroundActivatedEventArgs args)
    {
        //TODO
    }
}

有关单个流程后台任务的详细信息，请参阅Support your app with background tasks和Background activity with the Single Process Model。

UWP OnBackgroundActivated，没有找到合适的方法来覆盖

1 个答案: