Behaviors and Actions

Philip Colmer edited this page Sep 24, 2016 · 7 revisions

Table of Contents

  1. What is a XAML Behavior?
  2. EllipsisBehavior
  3. NavButtonBehavior
  4. DeviceDispositionBehavior
  5. BackButtonBehavior
  6. TextBoxEnterKeyBehavior
  7. KeyBehavior
  8. What is a XAML Action?
  9. CloseFlyoutAction
  10. ConditionalAction
  11. FocusAction
  12. OpenFlyoutAction
  13. TimeoutAction
  14. MessageDialogAction
  15. NavToPageAction

What is a XAML Behavior?

A XAML behavior is typically, though not necessarily, responsible for listening for a preconfigured or manually configured event.

XAML behaviors are a mechanism to encapsulate code with logic and configuration parameters such that it can then be declared in XAML without requiring code-behind. Most XAML Behaviors have design-time support. They can easily be written in C# and implement the simple interface IBehavior and typically contain XAML Actions IAction.

An example of a XAML behavior is the PropertyChangedBehavior (which is native to the framework) which waits for the value of a property to change (using INotifypropertyChanged). XAML behaviors, once triggered, invoke one or more XAML actions - also part of the behavior framework.

Syntax

[ContentProperty(Name = nameof(Actions))]
public class MyBehavior : DependencyObject, IBehavior
{
    public DependencyObject AssociatedObject { get; set; }

    public void Attach(DependencyObject associatedObject)
    {
        AssociatedObject = associatedObject;
    }

    public void Detach()
    {
        // TODO
    }

    public ActionCollection Actions
    {
        get
        {
            var actions = (ActionCollection)base.GetValue(ActionsProperty);
            if (actions == null)
                base.SetValue(ActionsProperty, actions = new ActionCollection());
            return actions;
        }
    }
    public static readonly DependencyProperty ActionsProperty = DependencyProperty.Register(nameof(Actions),
        typeof(ActionCollection), typeof(MyBehavior), new PropertyMetadata(null));
}

EllipsisBehavior

The intent of the EllipsisBehavior is to fix a flaw in the native XAML CommandBar control. By default, the ellipsis which is used to show additional elements is always visible, even when not necessary. This behavior allows the developer to specify whether the ellipsis is always Visible, Collapsed or Auto (determines visibility based upon whether there is content present).

This is valuable when your design requires you to remove the ellipse.

Syntax

<!--  header  -->
<controls:PageHeader Frame="{x:Bind Frame}" Text="{x:Bind ViewModel.Article.Headline, Mode=OneWay}">
    <Interactivity:Interaction.Behaviors>
        <Behaviors:EllipsisBehavior Visibility="Auto" />
    </Interactivity:Interaction.Behaviors>
</controls:PageHeader>

NavButtonBehavior

The intent of the NavButtonBehavior is to add behavior to any native XAML Button or AppBarButton. Once set to either [ Forward | Back ] then clicking the Button will navigate the referenced Frame accordingly.

This is valuable when wanting to create navigation buttons.

Syntax

<AppBarButton Icon="Forward" Label="Forward">
    <Interactivity:Interaction.Behaviors>
        <Behaviors:NavButtonBehavior Direction="Forward" Frame="{x:Bind Frame, Mode=OneWay}" />
    </Interactivity:Interaction.Behaviors>
</AppBarButton>

DeviceDispositionBehavior

The intent of the DeviceDispositionBehavior is to add behavior to any page that should occur on one or more specified device families. Note: this behavior is typically added to a top level element as it is listening to system events, (say transitioning to Continuum) rather than element level events.

This is valuable when you want to change some aspect of your apps behavior based upon one or more device families. An example could be hiding UIElements that are not applicable on a device, such as in-app back buttons on a Phone.

Properties

// true if the behavior applies to IoT devices; otherwise false
public bool IoT { get; set }
// true if the behavior applies to Xbox devices; otherwise false
public bool Xbox { get; set }
// true if the behavior applies to Team devices; otherwise false
// note: Team is the Surface Hub
public bool Team { get; set }
// true if the behavior applies to HoloLens devices; otherwise false
public bool HoloLens { get; set }
// true if the behavior applies to Desktop devices; otherwise false
public bool Desktop { get; set }
// true if the behavior applies to Mobile devices; otherwise false
public bool Mobile { get; set }
// true if the behavior applies to Phone devices; otherwise false
// note: determined if diagonal inches is less 7
public bool Phone { get; set }
// true if the behavior applies to Continuum devices; otherwise false
public bool Continuum { get; set }
// true if the behavior applies to Virtual devices; otherwise false
public bool Virtual { get; set }

Syntax

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <Interactivity:Interaction.Behaviors>
        <Behaviors:DeviceDispositionBehavior Desktop="True">
            <Core:GoToStateAction StateName="DesktopOnlyState"/>
        </Behaviors:DeviceDispositionBehavior>
    </Interactivity:Interaction.Behaviors>
</Grid>

BackButtonBehavior

The intent of the BackButtonBehavior is to add behavior to any page or view. The behavior will be triggered whenever the BootStrapper.BackRequested event is raised. Setting e.Handled = true in the code invoked by the behavior/action will prevent the system from executing a back navigation. Note: this behavior is typically added to a top level element as it is listening to the BootStrapper.BackRequested rather than element level events.

This is valuable when you want to intercept the BootStrapper.BackRequested and perform a specific action, then mark the event as handled. An example would be intecepting the BootStrapper.BackRequested event and closing a PopUp instead of navigating back.

Properties

none

Syntax

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <Interactivity:Interaction.Behaviors>
        <Behaviors:BackButtonBehavior>
            <Core:CallMethodAction MethodName="ClosePopUp" TargetObject="{Binding ElementName=page}"/>
        </Behaviors:BackButtonBehavior>
    </Interactivity:Interaction.Behaviors>
</Grid>

TextBoxEnterKeyBehavior

This is now obsolete - use KeyBehavior instead.

KeyBehavior

The intent of the KeyBehavior is to add behavior to any UIElement that supports key events. The behavior has properties that allow the developer to specifiy whether the action is performed on key up or key down, and whether modifier keys can also be used.

This is valuable when you wish to perform an action based upon a key press.

Properties

// The key that triggers the behavior
public VirtualKey Key { get; set; } = VirtualKey.None;
// true if Control must be held also; otherwise false
public bool AndControl { get; set; } = false;
// true if Alt must be held also; otherwise false
public bool AndAlt { get; set; } = false;
// true if Shift must be held also; otherwise false
public bool AndShift { get; set; } = false;
// Detemines if the behavior is triggered on the KeyUp or the KeyDown event
public Kinds Event { get; set; } = Kinds.KeyUp;

Syntax

<TextBox MinWidth="250" MinHeight="62"
            Header="Parameter to pass"
            Text="{Binding Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
    <Interactivity:Interaction.Behaviors>
        <!--  enable submit on enter key  -->
        <Behaviors:KeyBehavior Key="Enter">
            <Core:CallMethodAction MethodName="GotoDetailsPage" TargetObject="{Binding}" />
        </Behaviors:KeyBehavior>
        <!--  focus on textbox when page loads  -->
        <Core:EventTriggerBehavior>
            <Behaviors:FocusAction />
        </Core:EventTriggerBehavior>
    </Interactivity:Interaction.Behaviors>
</TextBox>

What is a XAML Action?

A XAML action (implementing IAction) does not typically listen to events, but instead takes some action - which is limited only by the developer's imagination.

An example of a XAML action is the ChangePropertyAction (which is native to the framework) which changes the value of some property to a new value, typically leveraging data-binding.

Syntax

public sealed class MyAction : DependencyObject, IAction
{
    public object Execute(object sender, object parameter)
    {
        // TODO
    }
}

CloseFlyoutAction

The intent of the CloseFlyoutAction is to close the first FlyOut parent in the Visual Tree. When invoked by a behavior, it will hunt up the XAML tree for the first FlyOut and set its IsOpen property to false.

This is valuable for small forms inside a FlyOut and is commonly used on Submit buttons in those forms.

Syntax

<Flyout x:Key="FormFlyout">
    <StackPanel>
        <TextBox Header="Name" Text="{x:Bind VM.Name, Mode=TwoWay}"/>
        <Button>
            <Interactivity:Interaction.Behaviors>
                <Core:EventTriggerBehavior EventName="Click">
                    <Behaviors:CloseFlyoutAction/>
                </Core:EventTriggerBehavior>
            </Interactivity:Interaction.Behaviors> Submit</Button>
    </StackPanel>
</Flyout>

ConditionalAction

The intent of the ConditionalAction is to prevent subsequent actions unless a condition is met. When invoked by a behavior, it will evaluate the condition and invoke child actions if the condition is met.

This is valuable if a child action cannot be executed until some condition is satisfied.

Syntax

<Button>
    <Core:EventTriggerBehavior EventName="Clicked"> 
        <b:ConditionalAction xmlns:b="using:Template10.Behaviors" 
            LeftValue="{Binding IsLoggedIn}" Operator="IsTrue"> 
            <Core:GoToStateAction StateName="LoggedInViewState" /> 
        </b:ConditionalAction> 
    </Core:EventTriggerBehavior> 
</Button>

FocusAction

The intent of the FocusAction is to call Control.Focus() on some referenced control. When invoked by a behavior, it will call Focus() and ignore if it succeed or not.

This is valuable in situations like Page.Load, focusing on the first element. It can also change the focus when used in conjunction with KeyBehavior.

Syntax

<TextBox MinWidth="250" MinHeight="62"
            Header="Parameter to pass"
            Text="{Binding Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
    <Interactivity:Interaction.Behaviors>
        <!--  enable submit on enter key  -->
        <Behaviors:KeyBehavior Key="Enter">
            <Core:CallMethodAction MethodName="GotoDetailsPage" TargetObject="{Binding}" />
        </Behaviors:KeyBehavior>
        <!--  focus on textbox when page loads  -->
        <Core:EventTriggerBehavior>
            <Behaviors:FocusAction />
        </Core:EventTriggerBehavior>
    </Interactivity:Interaction.Behaviors>
</TextBox>

OpenFlyoutAction

The intent of the OpenFlyoutAction is to open the FlyoutBase on the specified XAML element. When invoked by a behavior, it will look for the FlyOut and call Show().

This is valuable because it can be coupled with actions like ConditionalAction that can prevent the FlyOut until a condition. Or on controls that otherwise don't support a FlyOut.

Syntax

<AppBarButton Icon="Find" Label="Search">
	<FlyoutBase.AttachedFlyout>
		<Flyout>
			<StackPanel>
				<TextBlock Text="Awesome Flyout!" />
			</StackPanel>
		</Flyout>
	</FlyoutBase.AttachedFlyout>
	<Interactivity:Interaction.Behaviors>
		<Core:EventTriggerBehavior EventName="Tapped">
			<Behaviors:OpenFlyoutAction />
		</Core:EventTriggerBehavior>
	</Interactivity:Interaction.Behaviors>
</AppBarButton>

TimeoutAction

The intent of the TimeoutAction is to invoke child actions only after a specified number of seconds passes. When invoked by a behavior, a timer starts and child Actions are called once the time has passed.

This is valuable when you want to delay a response or invoke a secondary action after some time.

Syntax

<Button>
    <Interactivity:Interaction.Behaviors>
        <Core:EventTriggerBehavior EventName="Click">
            <Core:CallMethodAction MethodName="ShowBusy" TargetObject="{Binding Mode=OneWay}" />
            <Behaviors:TimeoutAction Milliseconds="5000">
                <Core:CallMethodAction MethodName="HideBusy" TargetObject="{Binding Mode=OneWay}" />
            </Behaviors:TimeoutAction>
        </Core:EventTriggerBehavior>
    </Interactivity:Interaction.Behaviors>
</Button>

MessageDialogAction

The intent of the MessageDialogAction is to display a ContentDialog with the specified Title, Content and option OkText values.

This is valuable when you want a simple way to show a notification dialog.

Properties

// The title of the dialog
public string Title { get; set }
// The content of the dialog
public string Content { get; set }
// The Ok Text of the dialog
public string OkText { get; set } = "Ok";

Syntax

<Button Content="Delete">
    <Interactivity:Interaction.Behaviors>
        <Core:EventTriggerBehavior EventName="Click">
            <Behaviors:MessageDialogAction Content="This is the Content" 
                                           Title="A Title"
                                           OkText="Agreed!"/>
        </Core:EventTriggerBehavior>
    </Interactivity:Interaction.Behaviors>
</Button>

NavToPageAction

This behavior is still in development.

The intent of the NavToPageAction is to navigate to the specified page using the supplied parameters. Note: Incomplete.

This is valuable when you want to simply navigate to page.

Properties

* **Frame**, Window.UI.XAML.Controls.Frame, required
* **Page**, string, required, full name (App.Views.MainPage)
* **Parameter**, string, optional
* **InfoOverride**, optional, Window.UI.XAML.Media.Animation.NavigationTransitionInfo

Syntax

<Button Content="Click me">
    <Interactivity:Interaction.Behaviors>
        <Core:EventTriggerBehavior EventName="Click">
            <b:NavToPageAction 
                Frame="{x:Bind Frame}" 
                Page="MultiplePageHeaders.Views.ContainerPage" />
        </Core:EventTriggerBehavior>
    </Interactivity:Interaction.Behaviors>
</Button>
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