Technology is fun isn’t it? As soon as you think you’ve figured out where things are heading a new technology comes onto
the scene, changes things up, and offers new opportunities. One of
the new technologies I’ve been spending quite a bit of time with lately is Windows 8 store applications. I posted my thoughts about Windows 8 during
the BUILD conference in 2011 and still feel excited about
the opportunity there. Time will tell how well it ends up being accepted by consumers but I’m hopeful that it’ll take off. I currently have two Windows 8 store application concepts I’m working on with one being built in XAML/C# and another in HTML/JavaScript. I really like that Microsoft supports both options since it caters to a variety of developers and makes it easy to get started regardless if you’re a desktop developer or Web developer. Here’s a quick look at how
the technologies are organized in Windows 8: In this post I’ll focus on
the basics of Windows 8 store XAML/C# apps by looking at features, files, and code provided by Visual Studio projects. To get started building these types of apps you’ll definitely need to have some knowledge of XAML and C#. Let’s get started by looking at
the Windows 8 store project types available in Visual Studio 2012. Windows 8 Store XAML/C# Project Types When you open Visual Studio 2012 you’ll see a new entry under C# named Windows Store. It includes 6 different project types as shown next.
The Blank App project provides initial starter code and a single page whereas
the Grid App and Split App templates provide quite a bit more code as well as multiple pages for your application.
The other projects available can be be used to create a class library project that runs in Windows 8 store apps, a WinRT component such as a custom control, and a unit test library project respectively. If you’re building an application that displays data in groups using
the “tile” concept then
the Grid App or Split App project templates are a good place to start. An example of
the initial screens generated by each project is shown next: Grid App Split View App When a user clicks a tile in a Grid App they can view details about
the tile data. With a Split View app groups/categories are shown and when
the user clicks on a group they can see a list of all
the different items and then drill-down into them: For
the remainder of this post I’ll focus on functionality provided by
the Blank App project since it provides a simple way to get started learning
the fundamentals of building Windows 8 store apps. Blank App Project Walkthrough
The Blank App project is a
great place to start since it’s simple and lets you focus on
the basics. In this post I’ll focus on what it provides you out of
the box and cover additional details in future posts. Once you have
the basics down you can move to
the other project types if you need
the functionality they provide.
The Blank App project template does exactly what it says – you get an empty project with a few starter files added to help get you going. This is a good option if you’ll be building an app that doesn’t fit into
the grid layout view that you see a lot of Windows 8 store apps following (such as on
the Windows 8 start screen). I ended up starting with
the Blank App project template for
the app I’m currently working on since I’m not displaying data/image tiles (something
the Grid App project does well) or drilling down into lists of data (functionality that
the Split App project provides).
The Blank App project provides images for
the tiles and splash screen (you’ll definitely want to change these), a StandardStyles.xaml resource dictionary that includes a lot of helpful styles such as buttons for
the AppBar (a special type of menu in Windows 8 store apps), an App.xaml file, and
the app’s main page which is named MainPage.xaml. It also adds a Package.appxmanifest that is used to define functionality that your app requires, app information used in
the store, plus more.
The App.xaml, App.xaml.cs and StandardStyles.xaml Files
The App.xaml file handles loading a resource dictionary named StandardStyles.xaml which has several key styles used throughout
the application: <Application
x:Class="BlankApp.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:BlankApp">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<!--
Styles that define common aspects of
the platform look and feel
Required by Visual Studio project and item templates
-->
<ResourceDictionary Source="Common/StandardStyles.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
StandardStyles.xaml has style definitions for different text styles and AppBar buttons. If you scroll down toward
the middle of
the file you’ll see that many AppBar button styles are included such as one for an edit icon. Button styles like this can be used to quickly and easily add icons/buttons into your application without having to be an expert in design.
<Style x:Key="EditAppBarButtonStyle" TargetType="ButtonBase" BasedOn="{StaticResource AppBarButtonStyle}">
<Setter Property="AutomationProperties.AutomationId" Value="EditAppBarButton"/>
<Setter Property="AutomationProperties.Name" Value="Edit"/>
<Setter Property="Content" Value=""/>
</Style>
Switching over to App.xaml.cs, it includes some code to help get you started. An OnLaunched() method is added to handle creating a Frame that child pages such as MainPage.xaml can be loaded into.
The Frame has
the same overall purpose as
the one found in WPF and Silverlight applications - it’s used to navigate between pages in an application.
/// <summary>
/// Invoked when
the application is launched normally by
the end user. Other entry points
/// will be used when
the application is launched to open a specific file, to display
/// search results, and so forth.
/// </summary>
/// <param name="args">Details about
the launch request and process.</param>
protected override void OnLaunched(LaunchActivatedEventArgs args)
{
Frame rootFrame = Window.Current.Content as Frame;
// Do not repeat app initialization when
the Window already has content,
// just ensure that
the window is active
if (rootFrame == null)
{
// Create a Frame to act as
the navigation context and navigate to
the first page
rootFrame = new Frame();
if (args.PreviousExecutionState == ApplicationExecutionState.Terminated)
{
//TODO: Load state from previously suspended application
}
// Place
the frame in
the current Window
Window.Current.Content = rootFrame;
}
if (rootFrame.Content == null)
{
// When
the navigation stack isn't restored navigate to
the first page,
// configuring
the new page by passing required information as a navigation
// parameter
if (!rootFrame.Navigate(typeof(MainPage), args.Arguments))
{
throw new Exception("Failed to create initial page");
}
}
// Ensure
the current window is active
Window.Current.Activate();
}
Notice that in addition to creating a Frame
the code also checks to see if
the app was previously terminated so that you can load any state/data that
the user may need when
the app is launched again. If you’re new to
the lifecycle of Windows 8 store apps
the following image shows how an app can be running, suspended, and terminated.
If
the user switches from an app they’re running
the app will be suspended in memory.
The app may stay suspended or may be terminated depending on how much memory
the OS thinks it needs so it’s important to save state in case
the application is ultimately terminated and has to be started fresh. Although I won’t cover saving application state here, additional information can be found at http://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh465099.aspx.
Another method in App.xaml.cs named OnSuspending() is also included in App.xaml.cs that can be used to store state as
the user switches to another application:
/// <summary>
/// Invoked when application execution is being suspended. Application state is saved
/// without knowing whether
the application will be terminated or resumed with
the contents
/// of memory still intact.
/// </summary>
/// <param name="sender">The source of
the suspend request.</param>
/// <param name="e">Details about
the suspend request.</param>
private void OnSuspending(object sender, SuspendingEventArgs e)
{
var deferral = e.SuspendingOperation.GetDeferral();
//TODO: Save application state and stop any background activity
deferral.Complete();
}
The MainPage.xaml and MainPage.xaml.cs Files
The Blank App project adds a file named MainPage.xaml that acts as
the initial screen for
the application. It doesn’t include anything aside from an empty <Grid> XAML element in it.
The code-behind class named MainPage.xaml.cs includes a constructor as well as a method named OnNavigatedTo() that is called once
the page is displayed in
the frame.
/// <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)
{
}
}
If you’re experienced with XAML you can switch to Design mode and start dragging and dropping XAML controls from
the ToolBox in Visual Studio. If you prefer to type XAML you can do that as well in
the XAML editor or while in split mode. Many of
the controls available in WPF and Silverlight are included such as Canvas, Grid, StackPanel, and Border for layout. Standard input controls are also included such as TextBox, CheckBox, PasswordBox, RadioButton, ComboBox, ListBox, and more. MediaElement is available for rendering video or playing audio files. Some of
the “common” XAML controls included out of
the box are shown next:
Although XAML/C# Windows 8 store apps don’t include all of
the functionality available in Silverlight 5,
the core functionality required to build store apps is there with additional functionality available in open source projects such as Callisto (started by Microsoft’s Tim Heuer), Q42.WinRT, and others. Standard XAML data binding can be used to bind C# objects to controls, converters can be used to manipulate data during
the data binding process, and custom styles and templates can be applied to controls to modify them. Although Visual Studio 2012 doesn’t support visually creating styles or templates, Expression Blend 5 handles that very well.
To get started building
the initial screen of a Windows 8 app you can start adding controls as mentioned earlier. Simply place them inside of
the <Grid> element that’s included. You can arrange controls in a stacked manner using
the StackPanel control, add a border around controls using
the Border control, arrange controls in columns and rows using
the Grid control, or absolutely position controls using
the Canvas control.
One of
the controls that may be new to you is
the AppBar. It can be used to add menu/toolbar functionality into a store app and keep
the app clean and focused. You can place an AppBar at
the top or bottom of
the screen. A user on a touch device can swipe up to display
the bottom AppBar or right-click when using a mouse. An example of defining an AppBar that contains an Edit button is shown next.
The EditAppBarButtonStyle is available in
the StandardStyles.xaml file mentioned earlier.
<Page.BottomAppBar>
<AppBar x:Name="ApplicationAppBar" Padding="10,0,10,0" AutomationProperties.Name="Bottom App Bar">
<Grid>
<StackPanel x:Name="RightPanel" Orientation="Horizontal" Grid.Column="1" HorizontalAlignment="Right">
<Button x:Name="Edit" Style="{StaticResource EditAppBarButtonStyle}" Tag="Edit" />
</StackPanel>
</Grid>
</AppBar>
</Page.BottomAppBar>
Like standard XAML controls,
the <Button> control in
the AppBar can be wired to an event handler method in
the MainPage.Xaml.cs file or even bound to a ViewModel object using “commanding” if your app follows
the Model-View-ViewModel (MVVM) pattern (check out
the MVVM Light package available through NuGet if you’re using MVVM with Windows 8 store apps).
The AppBar can be used to navigate to different screens, show and hide controls, display dialogs, show settings screens, and more.
The Package.appxmanifest File
The Package.appxmanifest file contains configuration details about your Windows 8 store app. By double-clicking it in Visual Studio you can define
the splash screen image, small and wide logo images used for tiles on
the start screen, orientation information, and more. You can also define what capabilities
the app has such as if it uses
the Internet, supports geolocation functionality, requires a microphone or webcam, etc. App declarations such as background processes, file picker functionality, and sharing can also be defined Finally, information about how
the app is packaged for deployment to
the store can also be defined.
Summary
If you already have some experience working with XAML technologies you’ll find that getting started building Windows 8 applications is pretty straightforward. Many of
the controls available in Silverlight and WPF are available making it easy to get started without having to relearn a lot of new technologies. In
the next post in this series I’ll discuss additional features that can be used in your Windows 8 store apps.
