WP7 - Animating add/remove item in a ListBox - silverlight

Question

I know you can achieve this in Silverlight 4 by playing with the ListBoxItem style's LayoutStates, i.e. BeforeUnloaded, BeforeLoaded and AfterLoaded.
It doesn't seem to be working at all in WP7 although these states exist in the default style.
I am currently using version 7.1.
Is there any way I can get this working?
Thanks,
Xin

Answer 1

for this I used Artefact Animator, it's for Silverlight but works perfectly for WP7 also. The code shows only the addition. Whole code from the project's sample page.
MainPage.xaml
<UserControl.Resources>
<!-- ADDS SMOOTH SCROLL -->
<ItemsPanelTemplate x:Key="ItemsPanelTemplate">
<StackPanel/>
</ItemsPanelTemplate>
</UserControl.Resources>
<Grid>
<ListBox x:Name="lb" Height="247" Width="100" ItemsPanel="{StaticResource ItemsPanelTemplate}" />
<Button x:Name="addBtn" Content="Add" Height="72" HorizontalAlignment="Left" Margin="159,145,0,0" VerticalAlignment="Top" Width="160" />
</Grid>
MainPage.xaml.cs
public partial class MainPage : PhoneApplicationPage
{
private static ScrollViewer _scrollViewer;
// Constructor
public MainPage()
{
InitializeComponent();
Loaded += MainPage_Loaded;
}
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
// INIT
lb.Items.Clear();
lb.UpdateLayout();
// SCROLL INTERACTION
_scrollViewer = FindVisualChild<ScrollViewer>(lb);
var bar = FindVisualChild<ScrollBar>(_scrollViewer);
if (bar != null)
bar.ValueChanged += (s, args) => SetValue(ListBoxScrollOffsetProperty, args.NewValue);
// INPUT
addBtn.Click += (s, args) => AddItem();
}
private void AddItem()
{
// Create New ListBoxItem
var lbi = new ListBoxItem
{
Content = "Item " + lb.Items.Count,
RenderTransform = new CompositeTransform
{
TranslateX = -lb.Width
},
};
// Add ListBoxItem
lb.Items.Add(lbi);
lb.UpdateLayout();
// Animate In Item
ArtefactAnimator.AddEase(lbi.RenderTransform, CompositeTransform.TranslateXProperty, 0, 1, AnimationTransitions.CubicEaseOut, 0);
ArtefactAnimator.AddEase(this, ListBoxScrollOffsetProperty, _scrollViewer.ScrollableHeight, .8, AnimationTransitions.CubicEaseOut, 0);
}
// LISTBOX SCROLL OFFSET
public static readonly DependencyProperty ListBoxScrollOffsetProperty =
DependencyProperty.Register("ListBoxScrollOffset", typeof(double), typeof(MainPage), new PropertyMetadata(0.0, OnListBoxScrollOffsetChanged));
private static void OnListBoxScrollOffsetChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
_scrollViewer.ScrollToVerticalOffset((double)e.NewValue);
}
public double ListBoxScrollOffset
{
get
{
return (double)GetValue(ListBoxScrollOffsetProperty);
}
set
{
SetValue(ListBoxScrollOffsetProperty, value);
}
}
// VISUAL HELPER
public static childItem FindVisualChild<childItem>(DependencyObject obj) where childItem : DependencyObject
{
for (var i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
{
var child = VisualTreeHelper.GetChild(obj, i);
if (child != null && child is childItem)
{
return (childItem)child;
}
else
{
var childOfChild = FindVisualChild<childItem>(child);
if (childOfChild != null)
{
return childOfChild;
}
}
}
return null;
}
}