private static void Expander_Collapsed(object sender, RoutedEventArgs e)
{
Expander expander = sender as Expander;
var child1 = VisualTreeHelper.GetChild(expander, 0);
var child2 = VisualTreeHelper.GetChild(child1, 0);
ExpanderResizer resizer = VisualTreeHelper.GetChild(child2, 1) as ExpanderResizer;
DoubleAnimation animation = new DoubleAnimation
{
To = 0,
Duration = TimeSpan.FromMilliseconds(300),
EasingFunction = new CubicEase {
EasingMode = EasingMode.EaseOut
}
};
if (expander.ExpandDirection == ExpandDirection.Up || expander.ExpandDirection == ExpandDirection.Down)
{
resizer.BeginAnimation(HeightProperty, animation);
}
else
{
resizer.BeginAnimation(WidthProperty, animation);
}
}
private static void OnExpenderContentChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (e.NewValue is Expander expander)
{
expander.Expanded += Expander_Expanded;
expander.Collapsed += Expander_Collapsed;
ExpanderResizer resizer = d as ExpanderResizer;
if (expander.ExpandDirection == ExpandDirection.Up || expander.ExpandDirection == ExpandDirection.Down)
{
resizer.Height = 0;
}
else
{
resizer.Width = 0;
}
}
}
private static void Expander_Expanded(object sender, RoutedEventArgs e)
{
Expander expander = sender as Expander;
var child1 = VisualTreeHelper.GetChild(expander, 0);
var child2 = VisualTreeHelper.GetChild(child1, 0);
Control control = VisualTreeHelper.GetChild(child2, 0) as Control;
ExpanderResizer resizer = VisualTreeHelper.GetChild(child2, 1) as ExpanderResizer;
UIElement element = resizer.Content as UIElement;
if (expander.ExpandDirection == ExpandDirection.Up || expander.ExpandDirection == ExpandDirection.Down)
{
element.Measure(new Size(resizer.ActualWidth, double.PositiveInfinity));
DoubleAnimation animation = new DoubleAnimation
{
To = element.DesiredSize.Height,
Duration = TimeSpan.FromMilliseconds(300),
EasingFunction = new CubicEase {
EasingMode = EasingMode.EaseOut
}
};
resizer.BeginAnimation(HeightProperty, animation);
}
else
{
element.Measure(new Size(expander.MaxWidth - control.ActualWidth, resizer.ActualHeight));
DoubleAnimation animation = new DoubleAnimation
{
To = element.DesiredSize.Width,
Duration = TimeSpan.FromMilliseconds(300),
EasingFunction = new CubicEase {
EasingMode = EasingMode.EaseOut
}
};
resizer.BeginAnimation(WidthProperty, animation);
}
}
