Quickstart: Update a live tile from a background task

發行項
10/06/2015

[This article is for Windows 8.x and Windows Phone 8.x developers writing Windows Runtime apps. If you’re developing for Windows 10, see the latest documentation]

Use a background task to update your app's live tile with fresh content.

Here's a video that shows how to add live tiles to your apps.

Prerequisites

This topic assumes that you can create a basic Windows Runtime app using C++, C#, or Visual Basic. For instructions on how to create your first Windows Store app, see Building your first Windows Runtime apps using C++, C#, or Visual Basic.

To use the code described in this section, you'll need:

Windows 8
Microsoft Visual Studio Express 2012 for Windows 8

Create the background task project

To enable a live tile for your app, add a new Windows Runtime Component project to your solution. This is a separate assembly that the OS loads and runs in the background when a user installs your app.

In Solution Explorer, right-click the solution, point to Add, and click or tap New Project.
In the Add New Project dialog, select the Windows Runtime Component template in the Visual C# > Windows Store section.
Name the project BackgroundTasks and click or tap OK. Microsoft Visual Studio adds the new project to the solution.
In the main project, add a reference to the BackgroundTasks project.

Implement the background task

Implement the IBackgroundTask interface to create a class that updates your app's live tile. Your background work goes in the Run method. In this case, the task gets a syndication feed for the MSDN blogs. To prevent the task from closing prematurely while asynchronous code is still running, get a deferral.

In Solution Explorer, rename the automatically generated file, Class1.cs, to BlogFeedBackgroundTask.cs.
In BlogFeedBackgroundTask.cs, replace the automatically generated code with the stub code for the BlogFeedBackgroundTask class.
In the Run method implementation, add code for the GetMSDNBlogFeed and UpdateTile methods.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

// Added during quickstart
using Windows.ApplicationModel.Background;
using Windows.Data.Xml.Dom;
using Windows.UI.Notifications;
using Windows.Web.Syndication;

namespace BackgroundTasks
{
    public sealed class BlogFeedBackgroundTask  : IBackgroundTask
    {
        public async void Run( IBackgroundTaskInstance taskInstance )
        {
            // Get a deferral, to prevent the task from closing prematurely 
            // while asynchronous code is still running.
            BackgroundTaskDeferral deferral = taskInstance.GetDeferral();

            // Download the feed.
            var feed = await GetMSDNBlogFeed();

            // Update the live tile with the feed items.
            UpdateTile( feed );

            // Inform the system that the task is finished.
            deferral.Complete();
        }

        private static async Task<SyndicationFeed> GetMSDNBlogFeed()
        {
            SyndicationFeed feed = null;

            try
            {
                // Create a syndication client that downloads the feed.  
                SyndicationClient client = new SyndicationClient();
                client.BypassCacheOnRetrieve = true;
                client.SetRequestHeader( customHeaderName, customHeaderValue );

                // Download the feed. 
                feed = await client.RetrieveFeedAsync( new Uri( feedUrl ) );
            }
            catch( Exception ex )
            {
                Debug.WriteLine( ex.ToString() );
            }

            return feed;
        }

        private static void UpdateTile( SyndicationFeed feed )
        {
            // Create a tile update manager for the specified syndication feed.
            var updater = TileUpdateManager.CreateTileUpdaterForApplication();
            updater.EnableNotificationQueue( true );
            updater.Clear();

            // Keep track of the number feed items that get tile notifications. 
            int itemCount = 0;

            // Create a tile notification for each feed item.
            foreach( var item in feed.Items )
            {
                XmlDocument tileXml = TileUpdateManager.GetTemplateContent( TileTemplateType.TileWideText03 );

                var title = item.Title;
                string titleText = title.Text == null ? String.Empty : title.Text;
                tileXml.GetElementsByTagName( textElementName )[0].InnerText = titleText;

                // Create a new tile notification. 
                updater.Update( new TileNotification( tileXml ) );

                // Don't create more than 5 notifications.
                if( itemCount++ > 5 ) break;
            }
        }

        // Although most HTTP servers do not require User-Agent header, others will reject the request or return 
        // a different response if this header is missing. Use SetRequestHeader() to add custom headers. 
        static string customHeaderName = "User-Agent";
        static string customHeaderValue = "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0)";

        static string textElementName = "text";
        static string feedUrl = @"https://blogs.msdn.com/b/MainFeed.aspx?Type=BlogsOnly";
    }
}

Set up the package manifest

To set up the package manifest, open it and add a new background task declaration. Set the entry point for the task to the class name, including its namespace.

In Solution Explorer, open Package.appxmanifest.
Click or tap the Declarations tab.
Under Available Declarations, select BackgroundTasks and click Add. Visual Studio adds BackgroundTasks under Supported Declarations.
Under Supported task types, ensure that Timer is checked.
Under App settings, set the entry point to BackgroundTasks.BlogFeedBackgroundTask.
Click or tap the Application UI tab.
Set Lock screen notifications to Badge and Tile Text.
Set a path to a 24x24 pixel icon in the Badge logo field. Important This icon must use monochrome and transparent pixels only.
In the Small logo field, set a path to a 30x30 pixel icon.
In the Wide logo field, set a path to a 310x150 pixel icon.

Register the background task

Create a BackgroundTaskBuilder to register your task.

Note

Starting in Windows 8.1, background task registration parameters are validated at the time of registration. An error is returned if any of the registration parameters are invalid. Your app must be able to handle scenarios where background task registration fails - for example, use a conditional statement to check for registration errors and then retry failed registration using different parameter values.

In your app’s main page, add the RegisterBackgroundTask method and call it in the OnNavigatedTo event handler.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Windows.ApplicationModel.Background;
using Windows.Data.Xml.Dom;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using Windows.Web.Syndication;

// The Blank Page item template is documented at https://go.microsoft.com/fwlink/p/?LinkID=234238

namespace ContosoApp
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        /// <summary>
        /// Invoked when this page is about to be displayed in a Frame.
        /// </summary>
        /// <param name="e">Event data that describes how this page was reached.  The Parameter
        /// property is typically used to configure the page.</param>
        protected override void OnNavigatedTo( NavigationEventArgs e )
        {
            this.RegisterBackgroundTask();
        }


        private async void RegisterBackgroundTask()
        {
            var backgroundAccessStatus = await BackgroundExecutionManager.RequestAccessAsync();
            if( backgroundAccessStatus == BackgroundAccessStatus.AllowedMayUseActiveRealTimeConnectivity ||
                backgroundAccessStatus == BackgroundAccessStatus.AllowedWithAlwaysOnRealTimeConnectivity )
            {
                foreach( var task in BackgroundTaskRegistration.AllTasks )
                {
                    if( task.Value.Name == taskName )
                    {
                        task.Value.Unregister( true );
                    }
                }

                BackgroundTaskBuilder taskBuilder = new BackgroundTaskBuilder();
                taskBuilder.Name = taskName;
                taskBuilder.TaskEntryPoint = taskEntryPoint;
                taskBuilder.SetTrigger( new TimeTrigger( 15, false ) );
                var registration = taskBuilder.Register();
            }
        }

        private const string taskName = "BlogFeedBackgroundTask";
        private const string taskEntryPoint = "BackgroundTasks.BlogFeedBackgroundTask";
    }
}

Debug the background task

To debug the background task, set a breakpoint in the task’s Run method. In the Debug Location toolbar, select your background task. This causes the system to call the Run method immediately.

Set a breakpoint in the task’s Run method.
Press F5 or tap Debug > Start Debugging to deploy and run the app.
After the app launches, switch back to Visual Studio.
Ensure that the Debug Location toolbar is visible. It's on the View > Toolbars menu.
On the Debug Location toolbar, click the Suspend dropdown and select BlogFeedBackgroundTask.
Visual Studio suspends execution at the breakpoint.
Press F5 or tap Debug > Continue to continue running the app.
Press Shift+F5 or tap Debug > Stop Debugging to stop debugging.
Return to the app's tile on the Start screen. After a few seconds, tile notifications appear on your app's tile.