How to animate appearing of an element - xaml

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! :)