WPF实现倒计时转场动画效果

using System;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Media.Effects;

namespace WPFDevelopers.Controls
{
    public enum CountdownTimerEffect
    {
        Default,
        MultiColor
    }
    public class CountdownTimer : ContentControl
    {
        private Storyboard storyboard;
        private const double seconds = 800;
        private double currentSeconds = seconds;
        private Grid myGrid;
        public int Number
        {
            get { return (int)GetValue(NumberProperty); }
            set { SetValue(NumberProperty, value); }
        }

        public static readonly DependencyProperty NumberProperty =
        DependencyProperty.Register("Number", typeof(int), typeof(CountdownTimer), new PropertyMetadata(3));


        /// <summary>
        /// 完成后回到开始
        /// </summary>
        public bool IsFinishStart
        {
            get { return (bool)GetValue(IsFinishStartProperty); }
            set { SetValue(IsFinishStartProperty, value); }
        }

        public static readonly DependencyProperty IsFinishStartProperty =
            DependencyProperty.Register("IsFinishStart", typeof(bool), typeof(CountdownTimer), new PropertyMetadata(false));



        public CountdownTimerEffect CountdownTimerEffect
        {
            get { return (CountdownTimerEffect)GetValue(CountdownTimerEffectProperty); }
            set { SetValue(CountdownTimerEffectProperty, value); }
        }

        public static readonly DependencyProperty CountdownTimerEffectProperty =
            DependencyProperty.Register("ExhibitionEnum", typeof(CountdownTimerEffect), typeof(CountdownTimer), new PropertyMetadata(CountdownTimerEffect.Default));



        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            NameScope.SetNameScope(this, new NameScope());
            if (FontSize == SystemFonts.CaptionFontSize)
                FontSize = 200;
            FontFamily = DrawingContextHelper.FontFamily;
            storyboard = new Storyboard();
            myGrid = new Grid();
            myGrid.Name = "myGrid";
            myGrid.ToolTip = "MouseDown";
            myGrid.Background = new SolidColorBrush(Colors.White);
            var linearGradient = new LinearGradientBrush
            {
                GradientStops = new GradientStopCollection
                {
                   new GradientStop{ Color = Colors.Red, Offset = 1 },
                   new GradientStop{ Color = Colors.White, Offset = 1 },
                   new GradientStop{ Color = Colors.White, Offset = .5 },
                   new GradientStop{ Color = Colors.Red, Offset = .5 },
                   new GradientStop{ Color = Colors.Red, Offset = 0 },
                   new GradientStop{ Color = Colors.White, Offset = 0 },
                },
                StartPoint = new Point(0.5, 0),
                EndPoint = new Point(10, 10),
                SpreadMethod = GradientSpreadMethod.Reflect,
                MappingMode = BrushMappingMode.Absolute
            };
            SolidColorBrush solidColor;
            this.RegisterName(myGrid.Name, myGrid);
            var num = 0;
            for (int i = Number; i >= num; i--)
            {
                var textBlock = new TextBlock();
                switch (CountdownTimerEffect)
                {
                    case CountdownTimerEffect.Default:
                        if (i % 2 == 0)
                            solidColor = Brushes.White;
                        else
                            solidColor = Brushes.Black;
                        textBlock.Foreground = solidColor;
                        break;
                    case CountdownTimerEffect.MultiColor:
                        textBlock.Foreground = linearGradient;
                        break;

                }

                textBlock.Text = i.ToString();
                textBlock.Name = $"textBlock{i}";
                textBlock.FontSize = FontSize;
                textBlock.FontWeight = FontWeights.ExtraBold;
                textBlock.VerticalAlignment = VerticalAlignment.Center;
                textBlock.HorizontalAlignment = HorizontalAlignment.Center;
                textBlock.RenderTransformOrigin = new Point(.5, .5);
                textBlock.Effect = new DropShadowEffect
                {
                    ShadowDepth = 2,
                    RenderingBias = RenderingBias.Performance,
                    Color = Colors.Red
                };
                if (!i.Equals(Number))
                    textBlock.Opacity = 0;
                textBlock.RenderTransform = new ScaleTransform
                {
                    ScaleX = 2,
                    ScaleY = 2,
                };
                this.RegisterName(textBlock.Name, textBlock);

                TimeSpan beginTime = TimeSpan.Zero;
                if (storyboard.Children.Count > 0)
                {
                    beginTime = TimeSpan.FromMilliseconds(currentSeconds);
                    currentSeconds += seconds;
                }
                var cubicEase = new CubicEase
                {
                    EasingMode = EasingMode.EaseIn,
                };
                DoubleAnimation doubleAnimationScaleX = new DoubleAnimation();
                doubleAnimationScaleX.From = 2;
                doubleAnimationScaleX.To = 0;
                doubleAnimationScaleX.EasingFunction = cubicEase;


                Storyboard.SetTargetName(doubleAnimationScaleX, textBlock.Name);
                Storyboard.SetTargetProperty(doubleAnimationScaleX, new PropertyPath("(TextBlock.RenderTransform).(ScaleTransform.ScaleX)"));

                var doubleAnimationScaleY = new DoubleAnimation
                {
                    From = 2,
                    To = 0,
                    EasingFunction = cubicEase
                };
                Storyboard.SetTargetName(doubleAnimationScaleY, textBlock.Name);
                Storyboard.SetTargetProperty(doubleAnimationScaleY, new PropertyPath("(TextBlock.RenderTransform).(ScaleTransform.ScaleY)"));




                doubleAnimationScaleX.BeginTime = beginTime;
                doubleAnimationScaleY.BeginTime = beginTime;
                doubleAnimationScaleX.Duration = TimeSpan.FromMilliseconds(seconds);
                doubleAnimationScaleY.Duration = TimeSpan.FromMilliseconds(seconds);
                if (!i.Equals(Number))
                {
                    var doubleAnimationOpacity = new DoubleAnimation
                    {
                        Duration = TimeSpan.FromMilliseconds(0),
                        BeginTime = beginTime,
                        From = 0,
                        To = 1
                    };
                    Storyboard.SetTargetName(doubleAnimationOpacity, textBlock.Name);
                    Storyboard.SetTargetProperty(doubleAnimationOpacity, new PropertyPath(TextBlock.OpacityProperty));
                    storyboard.Children.Add(doubleAnimationOpacity);
                }


                if (i % 2 == 0)
                {
                    var colorAnimation = new ColorAnimation
                    {
                        Duration = TimeSpan.FromMilliseconds(0),
                        From = Colors.White,
                        BeginTime = beginTime,
                        To = Colors.Black
                    };
                    Storyboard.SetTargetName(colorAnimation, myGrid.Name);
                    Storyboard.SetTargetProperty(colorAnimation, new PropertyPath("(Panel.Background).(SolidColorBrush.Color)"));
                    storyboard.Children.Add(colorAnimation);
                }
                else
                {
                    if (!i.Equals(Number))
                    {
                        var colorAnimation = new ColorAnimation
                        {
                            Duration = TimeSpan.FromMilliseconds(0),
                            BeginTime = beginTime,
                            From = Colors.Black,
                            To = Colors.White
                        };
                        Storyboard.SetTargetName(colorAnimation, myGrid.Name);
                        Storyboard.SetTargetProperty(colorAnimation, new PropertyPath("(Panel.Background).(SolidColorBrush.Color)"));
                        storyboard.Children.Add(colorAnimation);
                    }
                }


                storyboard.Children.Add(doubleAnimationScaleX);
                storyboard.Children.Add(doubleAnimationScaleY);


                myGrid.Children.Add(textBlock);
            }
            this.Content = myGrid;

        }

        protected override void OnMouseDown(MouseButtonEventArgs e)
        {
            base.OnMouseDown(e);

            if (storyboard != null && storyboard.Children.Count > 0)
            {
                storyboard.Completed += (s, y) =>
                {
                    myGrid.Background = new SolidColorBrush(Colors.White);
                    if (IsFinishStart)
                    {
                        var scaleTransform = new ScaleTransform
                        {
                            ScaleX = 2,
                            ScaleY = 2
                        };
                        var tb = myGrid.Children.Cast<TextBlock>().First();
                        tb.RenderTransform = scaleTransform;
                    }
                };
                storyboard.Begin(this);

            }

        }
    }
}

<UserControl x:Class="WPFDevelopers.Samples.ExampleViews.CountdownTimerExample"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:WPFDevelopers.Samples.ExampleViews"
             xmlns:wpfdev="https://github.com/yanjinhuagood/WPFDevelopers"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800">
   
    <Grid Margin="10" Grid.Row="1">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Border Margin="0,0,0,0" Background="{StaticResource WhiteSolidColorBrush}" CornerRadius="4,4,0,0" 
                    Effect="{StaticResource NormalShadowDepth}">
            <wpfdev:NavigateMenu TabStripPlacement="Top" SelectionChanged="NavigateMenu_SelectionChanged">
                <ListBoxItem Content="Default"/>
                <ListBoxItem Content="MultiColor"/>
            </wpfdev:NavigateMenu>
        </Border>
        <Border Grid.Row="1" Background="{StaticResource WhiteSolidColorBrush}" CornerRadius="0,0,4,4"
                    Effect="{StaticResource NormalShadowDepth}">
            <Grid Margin="10">
                <wpfdev:CountdownTimer Number="3" x:Name="CountdownTimer1"/>
                <UniformGrid Columns="4" Visibility="Collapsed" x:Name="CountdownTimerGroup">
                    <wpfdev:CountdownTimer Number="9" CountdownTimerEffect="MultiColor" FontSize="150" IsFinishStart="True"/>
                    <wpfdev:CountdownTimer Number="5" CountdownTimerEffect="MultiColor" FontSize="150" IsFinishStart="True"/>
                    <wpfdev:CountdownTimer Number="2" CountdownTimerEffect="MultiColor" FontSize="150" IsFinishStart="True"/>
                    <wpfdev:CountdownTimer Number="7" CountdownTimerEffect="MultiColor" FontSize="150" IsFinishStart="True"/>
                </UniformGrid>
            </Grid>
        </Border>
    </Grid>
</UserControl>

using System.Windows;
using System.Windows.Controls;

namespace WPFDevelopers.Samples.ExampleViews
{
    /// <summary>
    /// CountdownTimerExample.xaml 的交互逻辑
    /// </summary>
    public partial class CountdownTimerExample : UserControl
    {
        public CountdownTimerExample()
        {
            InitializeComponent();
        }

        private void NavigateMenu_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            var item = e.AddedItems[0] as ListBoxItem;
            if (item == null) return;
            switch (item.Content.ToString())
            {
                case "Default":
                    if(CountdownTimer1.Visibility != Visibility.Visible)
                    {
                        CountdownTimer1.Visibility = Visibility.Visible;
                        CountdownTimerGroup.Visibility = Visibility.Collapsed;
                    }
                    break;
                case "MultiColor":
                    if (CountdownTimerGroup.Visibility != Visibility.Visible)
                    {
                        CountdownTimerGroup.Visibility = Visibility.Visible;
                        CountdownTimer1.Visibility = Visibility.Collapsed;
                    }
                    break;
            }
        }
    }
}