Я использовал класс AnimationHelper, предоставленный Найджелом Шоу, и завернул его в многоразовый GridAnimationBehavior, который можно прикрепить к элементам RowDefinition и ColumnDefinition.
/// <summary>
/// Wraps the functionality provided by the <see cref="AnimationHelper"/> class
/// in a behavior which can be used with the <see cref="ColumnDefinition"/>
/// and <see cref="RowDefinition"/> types.
/// </summary>
public class GridAnimationBehavior : DependencyObject
{
#region Attached IsExpanded DependencyProperty
/// <summary>
/// Register the "IsExpanded" attached property and the "OnIsExpanded" callback
/// </summary>
public static readonly DependencyProperty IsExpandedProperty =
DependencyProperty.RegisterAttached("IsExpanded", typeof(bool), typeof(GridAnimationBehavior),
new FrameworkPropertyMetadata(OnIsExpandedChanged));
public static void SetIsExpanded(DependencyObject dependencyObject, bool value)
{
dependencyObject.SetValue(IsExpandedProperty, value);
}
#endregion
#region Attached Duration DependencyProperty
/// <summary>
/// Register the "Duration" attached property
/// </summary>
public static readonly DependencyProperty DurationProperty =
DependencyProperty.RegisterAttached("Duration", typeof(TimeSpan), typeof(GridAnimationBehavior),
new FrameworkPropertyMetadata(TimeSpan.FromMilliseconds(200)));
public static void SetDuration(DependencyObject dependencyObject, TimeSpan value)
{
dependencyObject.SetValue(DurationProperty, value);
}
private static TimeSpan GetDuration(DependencyObject dependencyObject)
{
return (TimeSpan)dependencyObject.GetValue(DurationProperty);
}
#endregion
#region GridCellSize DependencyProperty
/// <summary>
/// Use a private "GridCellSize" dependency property as a temporary backing
/// store for the last expanded grid cell size (row height or column width).
/// </summary>
private static readonly DependencyProperty GridCellSizeProperty =
DependencyProperty.Register("GridCellSize", typeof(double), typeof(GridAnimationBehavior),
new UIPropertyMetadata(0.0));
private static void SetGridCellSize(DependencyObject dependencyObject, double value)
{
dependencyObject.SetValue(GridCellSizeProperty, value);
}
private static double GetGridCellSize(DependencyObject dependencyObject)
{
return (double)dependencyObject.GetValue(GridCellSizeProperty);
}
#endregion
/// <summary>
/// Called when the attached <c>IsExpanded</c> property changed.
/// </summary>
private static void OnIsExpandedChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
{
var duration = GetDuration(dependencyObject);
var rowDefinition = dependencyObject as RowDefinition;
if (rowDefinition != null)
{
// The IsExpanded attached property of a RowDefinition changed
if ((bool)e.NewValue)
{
var expandedHeight = GetGridCellSize(rowDefinition);
if (expandedHeight > 0)
{
// Animate row height back to saved expanded height.
AnimationHelper.AnimateGridRowExpandCollapse(rowDefinition, true, expandedHeight, rowDefinition.ActualHeight, 0, duration);
}
}
else
{
// Save expanded height and animate row height down to zero.
SetGridCellSize(rowDefinition, rowDefinition.ActualHeight);
AnimationHelper.AnimateGridRowExpandCollapse(rowDefinition, false, rowDefinition.ActualHeight, 0, 0, duration);
}
}
var columnDefinition = dependencyObject as ColumnDefinition;
if (columnDefinition != null)
{
// The IsExpanded attached property of a ColumnDefinition changed
if ((bool)e.NewValue)
{
var expandedWidth = GetGridCellSize(columnDefinition);
if (expandedWidth > 0)
{
// Animate column width back to saved expanded width.
AnimationHelper.AnimateGridColumnExpandCollapse(columnDefinition, true, expandedWidth, columnDefinition.ActualWidth, 0, duration);
}
}
else
{
// Save expanded width and animate column width down to zero.
SetGridCellSize(columnDefinition, columnDefinition.ActualWidth);
AnimationHelper.AnimateGridColumnExpandCollapse(columnDefinition, false, columnDefinition.ActualWidth, 0, 0, duration);
}
}
}
}
Обратите внимание, что я немного подправил код Найджела, чтобы использовать параметр типа TimeSpan для длительности анимации вместо отдельных параметров секунд и миллисекунд.
Это поведение делает анимацию строк / столбцов сетки дружественной к MVVM (только для XAML, код не требуется). Пример:
<Grid.RowDefinitions>
<RowDefinition Height="*" Behaviors:GridAnimationBehavior.IsExpanded="{Binding IsUpperPaneVisible}" />
<RowDefinition Height="*" />
<RowDefinition Height="*" Behaviors:GridAnimationBehavior.IsExpanded="{Binding IsLowerPaneVisible}" />
</Grid.RowDefinitions>
Я добавил этот ответ, потому что в оригинальном плакате было запрошено чистое решение XAML.