uwp
UWP-bakgrundsuppgifter

Anmärkningar

Registrera en uppgift

/// <summary>
/// Registers a background task in the system waiting to trigger
/// </summary>
/// <param name="taskName">Name of the task. Has to be unique</param>
/// <param name="taskEntryPoint">Entry point (Namespace) of the class (has to implement IBackgroundTask and has to be in a Windows Runtime Component) to start</param>
/// <param name="trigger">What has to be triggered to start the task</param>
/// <param name="condition">Optional condition. Can be null</param>
/// <param name="recreateIfExists">Should the Task be recreated if it already exists?</param>
/// <returns></returns>
public BackgroundTaskRegistration RegisterTask(string taskName, string taskEntryPoint, IBackgroundTrigger trigger, IBackgroundCondition condition = null) {
    Debug.WriteLine("Try registering task: " + taskName);

    var builder = new BackgroundTaskBuilder {
        Name = taskName,
        TaskEntryPoint = taskEntryPoint
    };

    builder.SetTrigger(trigger);

    if (condition != null) {
        builder.AddCondition(condition);
    }

    try {
        var task = builder.Register();
        Debug.WriteLine("Task successfully registered");
        return task;
    } catch (Exception exception) {
        Debug.WriteLine("Error creating Task: " + exception);
        return null;
    }
}

Få en registrerad uppgift med namnet

/// <summary>
/// Gets a BackgroundTask by its name
/// </summary>
/// <param name="taskName">Name of the task to find</param>
/// <returns>The found Task or null if none found</returns>
public BackgroundTaskRegistration TaskByName(string taskName) =>
       BackgroundTaskRegistration.AllTasks.FirstOrDefault(x => x.Value.Name.Equals(taskName)).Value as BackgroundTaskRegistration;

Uppgiften

public sealed class BackgroundTask : IBackgroundTask {

    private BackgroundTaskDeferral _deferral;

    /// <summary>
    /// Registers the listener to check if the button is pressed
    /// </summary>
    /// <param name="taskInstance">An interface to an instance of the background task. The system creates this instance when the task has been triggered to run.</param>
    public async void Run(IBackgroundTaskInstance taskInstance) {
        _deferral = taskInstance.GetDeferral();

        //Do async operations here

        _deferral.Complete();
    }
}

Kontrollera om uppgiften är registrerad

private bool IsTaskRegistered(string taskName) =>
        BackgroundTaskRegistration.AllTasks.Any(x => x.Value.Name.Equals(taskName));

Aktivera en uppgift manuellt

var trigger = new ApplicationTrigger();
TaskHandlerMentionedInThisTutorial.RegisterTask(TaskName, entryPoint, trigger, null, true);    
await trigger.RequestAsync();

Avregistrerar en uppgift

/// <summary>
/// Unregister a single background task with given name
/// </summary>
/// <param name="taskName">task name</param>
/// <param name="cancelTask">true if task should be cancelled, false if allowed to finish</param>
public void UnregisterTask(string taskName, bool cancelTask) =>
    BackgroundTaskRegistration.AllTasks.First(x => x.Value.Name.Equals(taskName)).Value?.Unregister(cancelTask);

/// <summary>
/// Unregister an active group of background tasks, which name contains given string
/// </summary>
/// <param name="taskNamePart">part of the task name</param>
/// <param name="cancelTask">true if tasks should be cancelled, false if allowed to finish</param>
public void UnregisterTasks(string taskNamePart, bool cancelTask)
{
    foreach (var task in BackgroundTaskRegistration.AllTasks.Where(x => x.Value.Name.Contains(taskNamePart)))
        task.Value.Unregister(cancelTask);
}

Registrera bakgrundsuppgift med trigger

Bakgrundsuppgiften är ett bra sätt att utföra lite arbete medan din applikation inte körs. Innan du kan använda det måste du registrera dem.

Här är ett exempel på en bakgrundsuppgiftsklass inklusive registrering med en trigger och ett villkor och Run-implementeringen

public sealed class Agent : IBackgroundTask
{    
    public void Run(IBackgroundTaskInstance taskInstance)
    {
        // run the background task code
    }
    
    // call it when your application will start.
    // it will register the task if not already done
    private static IBackgroundTaskRegistration Register()
    {
        // get the entry point of the task. I'm reusing this as the task name in order to get an unique name
        var taskEntryPoint   = typeof(Agent).FullName;
        var taskName         = taskEntryPoint;
        
        // if the task is already registered, there is no need to register it again
        var registration            = BackgroundTaskRegistration.AllTasks.Select(x => x.Value).FirstOrDefault(x => x.Name == taskName);
        if(registration != null) return registration;
                        
        // register the task to run every 30 minutes if an internet connection is available
        var taskBuilder             = new BackgroundTaskBuilder();
        taskBuilder.Name            = taskName;
        taskBuilder.TaskEntryPoint  = taskEntryPoint;
        taskBuilder.SetTrigger(new TimeTrigger(30, false));
        taskBuilder.AddCondition(new SystemCondition(SystemConditionType.InternetAvailable));
        
        return taskBuilder.Register();
    }
}