Separate version

Net40/HandyControl_Net40/Controls/CoverView/CoverViewContent.cs

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+using System.Windows;
+using System.Windows.Controls;
+using HandyControl.Data;
+using HandyControl.Tools;
+using HandyControl.Tools.Extension;
+
+namespace HandyControl.Controls
+{
+    [TemplatePart(Name = ElementTriangle, Type = typeof(FrameworkElement))]
+    [TemplatePart(Name = ElementContent, Type = typeof(FrameworkElement))]
+    internal class CoverViewContent : ContentControl
+    {
+        private const string ElementTriangle = "PART_Triangle";
+
+        private const string ElementContent = "PART_Content";
+
+        private FrameworkElement _triangle;
+
+        private FrameworkElement _content;
+
+        internal bool WaitForUpdate { get; set; }
+
+        private int _index;
+
+        private int _groups;
+
+        private double _itemWidth;
+
+        private bool _isOpen;
+
+        internal bool CanSwitch { get; set; } = true;
+
+        internal bool IsOpen
+        {
+            get => _isOpen;
+            set
+            {
+                if (_isOpen == value) return;
+                _isOpen = value;
+                OpenSwitch(value);
+            }
+        }
+
+        public static readonly DependencyProperty ContentHeightProperty = DependencyProperty.Register(
+            "ContentHeight", typeof(double), typeof(CoverViewContent), new PropertyMetadata(ValueBoxes.Double300Box));
+
+        public double ContentHeight
+        {
+            get => (double) GetValue(ContentHeightProperty);
+            set => SetValue(ContentHeightProperty, value);
+        }
+
+        public override void OnApplyTemplate()
+        {
+            base.OnApplyTemplate();
+
+            _triangle = GetTemplateChild(ElementTriangle) as FrameworkElement;
+            _content = GetTemplateChild(ElementContent) as FrameworkElement;
+
+            if (WaitForUpdate)
+            {
+                _triangle.BeginAnimation(MarginProperty, AnimationHelper.CreateAnimation(new Thickness((_index % _groups + .5) * _itemWidth - _triangle.Width / 2, 0, 0, 0)));
+                OpenSwitch(_isOpen);
+                WaitForUpdate = false;
+            }
+        }
+
+        internal void UpdatePosition(int index, int groups, double itemWidth)
+        {
+            if (_triangle == null)
+            {
+                _index = index;
+                _groups = groups;
+                _itemWidth = itemWidth;
+                WaitForUpdate = true;
+                return;
+            }
+            _triangle.BeginAnimation(MarginProperty, AnimationHelper.CreateAnimation(new Thickness((index % groups + .5) * itemWidth - _triangle.Width / 2, 0, 0, 0)));
+        }
+
+        private void OpenSwitch(bool isOpen)
+        {
+            if (_content == null) return;
+            var animation = AnimationHelper.CreateAnimation(isOpen ? ContentHeight : 0);
+            _triangle.Show(false);
+            this.Show(true);
+            animation.Completed += (s, e) =>
+            {
+                CanSwitch = true;
+                this.Show(IsOpen);
+                if (IsOpen)
+                {
+                    _triangle.Show(true);
+                }
+            };
+            CanSwitch = false;
+            _content.BeginAnimation(HeightProperty, animation);
+        }
+    }
+}