WPF: Animate Height of ListView when final height is unknown

Question

I have a ListView, that is defined very simply in my XAML like so

<ListView Name="myListVew" MaxHeight="200" Visibility="Collapsed">
    <ListView.View>
        <GridView>
            <GridViewColumn Header="Line" Width="Auto" DisplayMemberBinding="{Binding Line}" />
            <GridViewColumn Header="Error" Width="Auto" DisplayMemberBinding="{Binding Error}" />
        </GridView>
    </ListView.View>
</ListView>

When I want the ListView to appear, I want to animate the height of the list view from 0. The problem is, I don't know the final height of the ListView since it will depend on how many items are shown inside it. Is there anyway of doing this?

Answer 1

Don't you hate it when you search for hours for a solution, post a question to a forum and then find the answer yourself 10 minutes later?

Anyway, I got it working by applying a layout scale transform like so

<DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Storyboard.TargetName="ErrorDisplay" Storyboard.TargetProperty="(FrameworkElement.LayoutTransform).(TransformGroup.Children)[0].(ScaleTransform.ScaleY)">
    <SplineDoubleKeyFrame KeyTime="00:00:00" Value="0"/>
    <SplineDoubleKeyFrame KeyTime="00:00:00.3000000" Value="1"/>
</DoubleAnimationUsingKeyFrames>

Answer 2

This isn't exactly the same scenario but it may help someone else.

I had a border that had a height of Auto and I wanted it to animate to a specific height.

My border looked like this:

<Border Name="ContainerBorder">
  <!-- Stuff... -->
</Border>

I created this storyboard:

<Storyboard x:Key="EditIn">
  <DoubleAnimation Storyboard.TargetProperty="Height"
                   Storyboard.TargetName="ContainerBorder"
                   Name="BorderAnimation"
                   To="45"
                   Duration="0:0:0.8" />
</Storyboard>

The button that triggered the animation had some codebehind:

private void Edit_Click(object sender, RoutedEventArgs e) {
  Storyboard sb = (Storyboard)FindResource("EditIn");
  //Find the border animation
  DoubleAnimation da = (DoubleAnimation)sb.Children.Where(t => t.Name == "BorderAnimation").FirstOrDefault();
  if (da != null) { da.From = ContainerBorder.ActualHeight; }
  sb.Begin(this);
}

So, I simply found the border and set the "From" property of the animation to the FrameworkElement's ActualHeight.