1 public class FluentSolidColorBrush : XamlCompositionBrushBase
  2 {
  3     Compositor Compositor => Window.Current.Compositor;
  4     ColorKeyFrameAnimation ColorAnimation;
  5     bool IsConnected;
  6 
  7     //被设置到控件属性时触发，例RootGrid.Background=new FluentSolidColorBrush();
  8     protected override void OnConnected()
  9     {
 10         if (CompositionBrush == null)
 11         {
 12             IsConnected = true;
 13 
 14             ColorAnimation = Compositor.CreateColorKeyFrameAnimation();
 15 
 16             //进度为0的关键帧，表达式为起始颜色。
 17             ColorAnimation.InsertExpressionKeyFrame(0f, "this.StartingValue");
 18 
 19             //进度为0的关键帧，表达式为参数名为Color的参数。
 20             ColorAnimation.InsertExpressionKeyFrame(1f, "Color");
 21 
 22             //创建颜色笔刷
 23             CompositionBrush = Compositor.CreateColorBrush(Color);
 24         }
 25     }
 26 
 27     //从属性中移除时触发，例RootGrid.Background=null;
 28     protected override void OnDisconnected()
 29     {
 30         if (CompositionBrush != null)
 31         {
 32             IsConnected = false;
 33 
 34             ColorAnimation.Dispose();
 35             ColorAnimation = null;
 36             CompositionBrush.Dispose();
 37             CompositionBrush = null;
 38 
 39             //清除已注册的事件。
 40             ColorChanged = null;
 41         }
 42     }
 43 
 44     public TimeSpan Duration
 45     {
 46         get { return (TimeSpan)GetValue(DurationProperty); }
 47         set { SetValue(DurationProperty, value); }
 48     }
 49 
 50     public static readonly DependencyProperty DurationProperty =
 51         DependencyProperty.Register("Duration", typeof(TimeSpan), typeof(FluentSolidColorBrush), new PropertyMetadata(TimeSpan.FromSeconds(0.4d), (s, a) =>
 52         {
 53             if (a.NewValue != a.OldValue)
 54             {
 55                 if (s is FluentSolidColorBrush sender)
 56                 {
 57                     if (sender.ColorAnimation != null)
 58                     {
 59                         sender.ColorAnimation.Duration = (TimeSpan)a.NewValue;
 60                     }
 61                 }
 62             }
 63         }));
 64 
 65     public Color Color
 66     {
 67         get { return (Color)GetValue(ColorProperty); }
 68         set { SetValue(ColorProperty, value); }
 69     }
 70 
 71     public static readonly DependencyProperty ColorProperty =
 72         DependencyProperty.Register("Color", typeof(Color), typeof(FluentSolidColorBrush), new PropertyMetadata(default(Color), (s, a) =>
 73         {
 74             if (a.NewValue != a.OldValue)
 75             {
 76                 if (s is FluentSolidColorBrush sender)
 77                 {
 78                     if (sender.IsConnected)
 79                     {
 80                         //给ColorAnimation，进度为1的帧的参数Color赋值
 81                         sender.ColorAnimation.SetColorParameter("Color", (Color)a.NewValue);
 82 
 83                         //创建一个动画批，CompositionAnimation使用批控制动画完成。
 84                         var batch = sender.Compositor.CreateScopedBatch(CompositionBatchTypes.Animation);
 85 
 86                         //批内所有动画完成事件，完成时如果画刷没有Disconnected，则触发ColorChanged
 87                         batch.Completed += (s1, a1) =>
 88                         {
 89                             if (sender.IsConnected)
 90                             {
 91                                 sender.OnColorChanged((Color)a.OldValue, (Color)a.NewValue);
 92                             }
 93                         };
 94                         sender.CompositionBrush.StartAnimation("Color", sender.ColorAnimation);
 95                         batch.End();
 96                     }
 97                 }
 98             }
 99         }));
100 
101     public event ColorChangedEventHandler ColorChanged;
102     private void OnColorChanged(Color oldColor, Color newColor)
103     {
104         ColorChanged?.Invoke(this, new ColorChangedEventArgs()
105         {
106             OldColor = oldColor,
107             NewColor = newColor
108         });
109     }
110 }
111 
112 public delegate void ColorChangedEventHandler(object sender, ColorChangedEventArgs args);
113 public class ColorChangedEventArgs : EventArgs
114 {
115     public Color OldColor { get; internal set; }
116     public Color NewColor { get; internal set; }
117 }

 1 public class TransitionsHelper : DependencyObject
 2 {
 3     public static Brush GetBackground(FrameworkElement obj)
 4     {
 5         return (Brush)obj.GetValue(BackgroundProperty);
 6     }
 7 
 8     public static void SetBackground(FrameworkElement obj, Brush value)
 9     {
10         obj.SetValue(BackgroundProperty, value);
11     }
12 
13     public static TimeSpan GetDuration(FrameworkElement obj)
14     {
15         return (TimeSpan)obj.GetValue(DurationProperty);
16     }
17 
18     public static void SetDuration(FrameworkElement obj, TimeSpan value)
19     {
20         obj.SetValue(DurationProperty, value);
21     }
22 
23     public static readonly DependencyProperty BackgroundProperty =
24         DependencyProperty.RegisterAttached("Background", typeof(Brush), typeof(TransitionsHelper), new PropertyMetadata(null, BackgroundPropertyChanged));
25 
26     public static readonly DependencyProperty DurationProperty =
27         DependencyProperty.RegisterAttached("Duration", typeof(TimeSpan), typeof(TransitionsHelper), new PropertyMetadata(TimeSpan.FromSeconds(0.6d)));
28 
29     private static void BackgroundPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
30     {
31         if (e.NewValue != e.OldValue)
32         {
33             if (d is FrameworkElement sender)
34             {
35                 //拿到New和Old的Brush，因为Brush可能不是SolidColorBrush，这里不能使用强制类型转换。
36                 var NewBrush = e.NewValue as SolidColorBrush;
37                 var OldBrush = e.OldValue as SolidColorBrush;
38 
39                 //下面分别获取不同控件的Background依赖属性。
40                 DependencyProperty BackgroundProperty = null;
41                 if (sender is Panel)
42                 {
43                     BackgroundProperty = Panel.BackgroundProperty;
44                 }
45                 else if (sender is Control)
46                 {
47                     BackgroundProperty = Control.BackgroundProperty;
48                 }
49                 else if (sender is Shape)
50                 {
51                     BackgroundProperty = Shape.FillProperty;
52                 }
53 
54                 if (BackgroundProperty == null) return;
55 
56                 //如果当前笔刷是FluentSolidColorBrush,就将当前笔刷设置成旧笔刷，触发FluentSolidColorBrush的OnDisconnected，
57                 //OnDisconnected中会清理掉ColorChanged上注册的事件，防止笔刷在卸载之后，动画完成时触发事件，导致运行不正常。
58                 if (sender.GetValue(BackgroundProperty) is FluentSolidColorBrush tmp_fluent)
59                 {
60                     sender.SetValue(BackgroundProperty, OldBrush);
61                 }
62 
63                 //如果OldBrush或者NewBrush中有一个为空，就不播放动画，直接赋值
64                 if (OldBrush == null || NewBrush == null)
65                 {
66                     sender.SetValue(BackgroundProperty, NewBrush);
67                     return;
68                 }
69 
70                 var FluentBrush = new FluentSolidColorBrush()
71                 {
72                     Duration = GetDuration(sender),
73                     Color = OldBrush.Color,
74                 };
75                 FluentBrush.ColorChanged += (s, a) =>
76                 {
77                     sender.SetValue(BackgroundProperty, NewBrush);
78                 };
79                 sender.SetValue(BackgroundProperty, FluentBrush);
80                 FluentBrush.Color = NewBrush.Color;
81             }
82         }
83     }
84 }