xaml programming

XAML PROGRAMMINGWindows Phone User Group, Singapore. 26 April 2014

TOPICS

• Intro to XAML

• XAML UI Elements

• Controls

• Data Binding

• MVVM

EXTENSIBLE APPLICATION MARKUP LANGUAGESerialization and Initialization format

<Activity x:TypeArguments="x:Int32" x:Class="Add" xmlns="http://schemas.microsoft.com/netfx/2009/xaml/activities" > <x:Members> <x:Property Name="Operand1" Type="InArgument(x:Int32)" /> < x:Property Name="Operand2" Type="InArgument(x:Int32)" /> </x:Members> <Sequence> <Assign x:TypeArguments="x:Int32" Value="[Operand1 + Operand2]"> <Assign.To> <OutArgument x:TypeArguments="x:Int32"> <ArgumentReference x:TypeArguments="x:Int32" ArgumentName="Result"/> </OutArgument> </Assign.To> </Assign> </Sequence> </Activity>

XAML - USER INTERFACE Declarative

Toolable

Recommended

<Page x:Class="App12.MainPage"…> <Grid> <Grid.Resources> <Style x:Key="PinkButton" TargetType="Button"> <Setter Property="Background" Value="Pink" /> </Style> </Grid.Resources>

<Button x:Name="myButton" Style="{StaticResource PinkButton}" Content="{Binding data.buttonName}" Click="OnButtonClick" Width="300" Margin="250" VerticalAlignment="Stretch"> </Button> </Grid>

</Page>

DECLARATIVE

Button b = new Button();b.Width = 100;b.Height = 50;b.Content = "Click Me!"; b.Background = new SolidColorBrush( Colors.Green);

<Button Content="Click Me!" Width="100" Height="50" Background="Green“ />

UI ELEMENTSBrushes, Shapes, Styles &Properties

STYLES

<ResourceDictionary

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

<Style x:Key="RecipeTitle" TargetType="TextBlock">

<Setter Property="Foreground" Value="Orange" />

<Setter Property="FontSize" Value="24"/>

</Style>

</ResourceDictionary>

DEPENDENCY PROPERTIES

• Special properties that power most of the presentation engine features

- Data Binding- Styling- Attached Properties- Animation- Property Invalidation- Property Inheritance- Default Values- Sparse Storage

DEFINING DEPENDENCY PROPERTIES

• Inherit from DependencyObject

• Call DependencyObject.Register

• Create standard property

public static readonly DependencyProperty RadiusProperty = DependencyProperty.Register("Radius", typeof(double), typeof(CarouselPanel), new PropertyMetadata(200.0, new PropertyChangedCallback(CarouselPanel.RadiusChanged)));

// optional but convenient public double Radius{ get { return (double)this.GetValue(RadiusProperty); } set {

this.SetValue(RadiusProperty, value); }}

ATTACHED PROPERTIES

• Inherit from DependencyObject

• Call DependencyProperty.RegisterAttach

• Create two static methods Getnnn/Setnnn

public static readonly DependencyProperty RowProperty = DependencyProperty.RegisterAttached("Row", typeof(int), typeof(Grid), new PropertyMetadata(0, new PropertyChangedCallback(OnRowChanged)));

public static void SetRow(DependencyObject obj, int value){ obj.SetValue(RowProperty, value); }

public static int GetRow(DependencyObject obj ){ return (int) obj.GetValue(RowProperty); }

LAYOUTSControl Layouts

PROPERTIES AFFECTING LAYOUT• Width/Height

• HorizontalAlignment/VerticalAlignment

• Margin

• Padding

• Visibility

MARGIN • Space outside edges of an element

<StackPanel Orientation="Horizontal" Height="200" Background="AliceBlue"> <Rectangle Width="100" Height="100" Fill="Yellow" /> <Rectangle Width="100" Height="100" Fill="Green"/> <Rectangle Width="100" Height="100" Fill="Yellow" Margin="30"/> <Rectangle Width="100" Height="100" Fill="Green" Margin="50"/> <Rectangle Width="100" Height="100" Fill="Yellow" Margin="80"/> </StackPanel>

PADDING • Space inside edges of an element

<Border Width="300" Height="300" Background="Yellow" Padding="40“ > <Rectangle Fill="Red" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" /> </Border> <Border Width="300" Height="300" Background="Yellow" Padding="100,5" Margin="449,112,617,356"> <Rectangle Fill="Red" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/></Border>

DATA BINDINGDeclarative

DATA BINDING SCENARIOS AND BENEFITS

Connects UI to data• When data values change, UI updates• If two-way: when user provides input, the data is updated too

Decreases code

Enables templating

COMPONENTS OF UI DATA BINDING• A Binding consists of 4 components:

1. Source2. Source path3. Target dependency object4. Target dependency property

Binding Target Binding Source

Object

PropertyProperty

Dependency Object

Dependency Property

Dependency Property

Binding Object

BINDING COMPONENTS IN XAML1. Source2. Source path3. Target dependency object4. Target dependency property

<TextBox IsEnabled="{Binding ElementName=MyCheckBox,Path=IsChecked}"/>

Target Dependency Property Source Path

Target Dependency Object

Source

BINDING TO NON-DPS

• Any public property on a CLR object will do

• Simple properties only read once by default• Can update manually

• Updates occur only if notifications available• INotifyPropertyChanged

INOTIFYPROPERTYCHANGED• Defines the PropertyChanged event

• Of type PropertyChangedEventHandler

CONVERTERSpublic class BoolToVisibilityConverter : IValueConverter{ public object Convert(object value, Type targetType, object parameter, string language){ bool val = (bool) value ; return ( val ? Visibility.Visible : Visibility.Collapsed) ; }

public object ConvertBack(object value, Type targetType, object parameter, string language) { var vis = (Visibility)value; return vis == Visibility.Visible; }}

DATATEMPLATE & CONTENT MODEL

• Some controls house content:• ContentControl: Contains a single item• ItemsControl: Contains a collection of items

• More generally:• Anything with a ContentPresenter

• Enables use of a DataTemplate

MVVMModel-View-ViewModel

Presentation Model(ViewModel)

MVVM

Model View

Databinding

Databinding

The relationships

View

ViewModel

DataBinding Commands ServicesMessages

Model

BENEFITS

• During the development process, developers and designers can work more independently and concurrently on their components. The designers can concentrate on the view, and if they are using Expression Blend, they can easily generate sample data to work with, while the developers can work on the view model and model components.

• The developers can create unit tests for the view model and the model without using the view. The unit tests for the view model can exercise exactly the same functionality as used by the view.

• It is easy to redesign the UI of the application without touching the code because the view is implemented entirely in XAML. A new version of the view should work with the existing view model.

• If there is an existing implementation of the model that encapsulates existing business logic, it may be difficult or risky to change. In this scenario, the view model acts as an adapter for the model classes and enables you to avoid making any major changes to the model code.