How to animate appearing of an element

Question

I have an question about Expression Blend 4.

I want to create a simple component appearing animation, when height of component changes from 0 to 100% and components below it are moving down to allocate required space.

My problem is that only static values in pixels allowed to create such type of animation. But I did not know height of my control (actually, it is textBox in which content and content length may vary), and I cannot set Height value of last keyframe to Auto.

What should I do to implement this task?

Thanks in advance.

Answer 1

I guess the easist way would be using the Fluid Layout.

In the below example I created a TextBlock and set its Visibility to Collpased. Then when the Show visual state is triggered, I set its Visibility to Visible. Normally you can't animate the Visibility but if you enable the Fluid Layout behavior (also remember to define a TransitionEffect), it will animate it for you automatically.

<UserControl
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions" xmlns:ee="http://schemas.microsoft.com/expression/2010/effects" xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" mc:Ignorable="d"
    x:Class="transformanimation.MainPage"
    Width="640" Height="480">
    <UserControl.Resources>
        <Storyboard x:Name="Storyboard1">
            <DoubleAnimation Duration="0:0:0.7" To="0.2" Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.ScaleX)" Storyboard.TargetName="textBlock" d:IsOptimized="True"/>
            <DoubleAnimation Duration="0:0:0.7" To="0.2" Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.ScaleY)" Storyboard.TargetName="textBlock" d:IsOptimized="True"/>
        </Storyboard>
    </UserControl.Resources>

    <Grid x:Name="LayoutRoot" Background="White">
        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup x:Name="VisualStateGroup" ei:ExtendedVisualStateManager.UseFluidLayout="True">
                <VisualStateGroup.Transitions>
                    <VisualTransition GeneratedDuration="0:0:0.2">
                        <ei:ExtendedVisualStateManager.TransitionEffect>
                            <ee:FadeTransitionEffect/>
                        </ei:ExtendedVisualStateManager.TransitionEffect>
                    </VisualTransition>
                </VisualStateGroup.Transitions>
                <VisualState x:Name="Hide"/>
                <VisualState x:Name="Show">
                    <Storyboard>
                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="textBlock">
                            <DiscreteObjectKeyFrame KeyTime="0">
                                <DiscreteObjectKeyFrame.Value>
                                    <Visibility>Visible</Visibility>
                                </DiscreteObjectKeyFrame.Value>
                            </DiscreteObjectKeyFrame>
                        </ObjectAnimationUsingKeyFrames>
                    </Storyboard>
                </VisualState>
            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
        <VisualStateManager.CustomVisualStateManager>
            <ei:ExtendedVisualStateManager/>
        </VisualStateManager.CustomVisualStateManager>
        <Grid Margin="205,96,275,150">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition/>
            </Grid.RowDefinitions>
            <TextBlock x:Name="textBlock" TextWrapping="Wrap" Text="TextBlock" FontSize="26.667" RenderTransformOrigin="0.5,0.5" Visibility="Collapsed">
                <TextBlock.RenderTransform>
                    <CompositeTransform/>
                </TextBlock.RenderTransform>
            </TextBlock>
            <Rectangle Fill="#FF767689" Stroke="Black" Grid.Row="1"/>
        </Grid>
        <Button Content="hide" HorizontalAlignment="Left" VerticalAlignment="Top" Width="75" Margin="63,19,0,0">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="Click">
                    <ei:GoToStateAction StateName="Hide"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </Button>
        <Button Content="show" HorizontalAlignment="Left" VerticalAlignment="Top" Width="75" Margin="183,20,0,0">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="Click">
                    <ei:GoToStateAction StateName="Show"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </Button>
    </Grid>
</UserControl>

Of course if you don't want to use this magicial animation you can try animating its ScaleY. Something like this,

        <DoubleAnimation Duration="0:0:0.2" To="0" Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.ScaleY)" Storyboard.TargetName="textBlock" d:IsOptimized="True"/>

Hope this helps! :)