月更

AntDesignWPF/Behaviors/VisibilityBehavior.cs

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+using System.Windows;
+using System.Windows.Media.Animation;
+
+using Microsoft.Xaml.Behaviors;
+namespace AntDesign.WPF.Behaviors
+{
+    /// <summary>
+    /// Provides the ability to animate when changing the Visibility property for an element.
+    /// </summary>
+    public class VisibilityBehavior : Behavior<FrameworkElement>
+    {
+        #region Fields
+
+        private Visibility visibility;
+
+        #endregion
+
+        #region Properties
+
+        public static readonly DependencyProperty AppearProperty =
+            DependencyProperty.Register("Appear", typeof(Storyboard), typeof(VisibilityBehavior), new PropertyMetadata(null));
+
+        /// <summary>
+        /// Gets/sets the storyboard when the element is visible.
+        /// </summary>
+        public Storyboard Appear
+        {
+            get { return (Storyboard)GetValue(AppearProperty); }
+            set { SetValue(AppearProperty, value); }
+        }
+
+        public static readonly DependencyProperty LeaveProperty =
+            DependencyProperty.Register("Leave", typeof(Storyboard), typeof(VisibilityBehavior), new PropertyMetadata(null));
+
+        /// <summary>
+        /// Gets/sets the storyboard when the element is hidden.
+        /// </summary>
+        public Storyboard Leave
+        {
+            get { return (Storyboard)GetValue(LeaveProperty); }
+            set { SetValue(LeaveProperty, value); }
+        }
+
+        #endregion
+
+        #region Overrides
+
+        protected override void OnAttached()
+        {
+            visibility = AssociatedObject.Visibility;
+            AssociatedObject.IsVisibleChanged += OnVisibleChanged;
+
+            base.OnAttached();
+        }
+
+        private void OnLoaded(object sender, RoutedEventArgs e)
+        {
+            AssociatedObject.IsVisibleChanged += OnVisibleChanged;
+        }
+
+        protected override void OnDetaching()
+        {
+            AssociatedObject.IsVisibleChanged -= OnVisibleChanged;
+
+            base.OnDetaching();
+        }
+
+        #endregion
+
+        #region Private Methods
+
+        private void OnVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
+        {
+            if (visibility == AssociatedObject.Visibility) return;
+
+            Storyboard storyboard;
+            
+            if (AssociatedObject.Visibility == Visibility.Visible)
+            {
+                if (Appear == null) return;
+
+                storyboard = Appear;
+                visibility = AssociatedObject.Visibility;
+
+            } else
+            {
+                if (Leave == null) return;
+
+                var cache = AssociatedObject.Visibility;
+                AssociatedObject.SetCurrentValue(UIElement.VisibilityProperty, visibility = Visibility.Visible);
+
+                storyboard = Leave.Clone();
+                storyboard.Completed += (s, a) => AssociatedObject.SetCurrentValue(UIElement.VisibilityProperty, visibility = cache);
+            }
+
+            AssociatedObject.BeginStoryboard(storyboard);
+        }
+
+        #endregion
+    }
+}