How to Animate a ContentControl in a ItemsControl - wpf

Question

I like to use the ItemsControl to host ContentsControls. Each new ContentsControl is animating its contents when the item gets added and each ContentControl and overlays the previous one. The ItemsControl and the ContentControl Content is bound with Caliburn Micro using Naming conventions.
<ItemsControl x:Name="OverlayStackedItems" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Background="Transparent">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Grid x:Name="ItemsHost" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<cc:DummyContentControl cal:View.Model="{Binding}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
The ContentControl is defined like this:
[ContentProperty("Content")]
public partial class DummyContentControl :ContentControl
{
public DummyContentControl()
{
}
static DummyContentControl()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(DummyContentControl), new FrameworkPropertyMetadata(typeof(ContentControl)));
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
}
protected override void OnContentChanged(object oldContent, object newContent)
{
LayoutUpdated += (sender, e) =>
{
};
UpdateLayout();
base.OnContentChanged(oldContent, newContent);
}
void DummyContentControl_LayoutUpdated(object sender, EventArgs e)
{
throw new NotImplementedException();
}
protected override Size MeasureOverride(Size constraint)
{
return base.MeasureOverride(constraint);
}
}
So now finally my question. In the real ContentControl I like to animate the Content but
the ContentControl has the size of 0 when OnContentChange is called where my Animation gets created. The orders of calls when the ContentControl is hosted in the ItemsControl is:
OnContentChanged (Animation failes)
OnApplyTemplate
MeasureOverride
When the ContentControl runs by itself the order is:
OnApplyTemplate
MeasureOverride
OnContentChanged (Animation works)
The problem here is that the complete visual subtree of the new Item in the ItemsControl is 0 (DesiredSize,ActualSize = 0) therefore my animation code fails.
I hope that makes some sense to somebody,
Any help would be great, Thx,J
------------------------------Revision-------------------
Ok I added the OnLoaded eventhandler to the ctor of the DummyControl. The order of calles is
1. OnContentChanged (all sizes are 0)
2. OnApplyTemplate (all sizes are 0)
3. MeasureOverride (called several Times probably for all child controls hostet by the ContentControl)
4. Loaded event (Desired Size is set all other sizes are still 0)
Can sombody explain what the recommanded practice is on how to animate a ContentControl
hostet by an ItemsControl?

Answer 1

Just do everything in XAML and let the animation do it's thing, without calling MeasureOverride() and the rest of the hooks.
<ItemsControl>
<ItemsControl.ItemContainerStyle>
<Style>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<Border>
<TextBlock Text="Whatever your template should look like"/>
</Border>
<ControlTemplate.Triggers>
<EventTrigger RoutedEvent="FrameworkElement.Loaded">
<BeginStoryboard>
<Storyboard >
<DoubleAnimation Storyboard.TargetProperty="(Border.RenderTransform).(ScaleTransform.ScaleX)" Duration="0:0:0.5" From="0" To="1" />
<DoubleAnimation Storyboard.TargetProperty="(Border.RenderTransform).(ScaleTransform.ScaleY)" Duration="0:0:0.5" From="0" To="1" />
<DoubleAnimation Storyboard.TargetProperty="(Border.RenderTransform).(ScaleTransform.CenterX)" Duration="0:0:0.5" To="25" />
<DoubleAnimation Storyboard.TargetProperty="(Border.RenderTransform).(ScaleTransform.CenterY)" Duration="0:0:0.5" To="25" />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ItemsControl.ItemContainerStyle>
</ItemsControl>