本示例演示如何对 GradientStop 对象的 Color 和 Offset 进行动画处理。
示例
下面的示例对 LinearGradientBrush 中的三个渐变停止点进行动画处理。 本示例使用三个动画，每个动画都对一个不同的渐变停止点进行动画处理：
第一个动画（即 DoubleAnimation）对第一个渐变停止点的 Offset 进行动画处理，使其从 0.0 到 1.0 然后回到 0.0。 因此，该渐变中的第一种颜色会从矩形的左侧移动到右侧，然后移动回到左侧。
第二个动画（即 ColorAnimation）对第二个渐变停止点的 Color 进行动画处理，使从 Purple 变为 Yellow 然后又变回 Purple。 因此，该渐变中位于中间的颜色会从紫色改为黄色，之后又改回紫色。
第三个动画（即另一个 ColorAnimation）以 -1 为增量对第三个渐变停止点的 Color 的不透明度进行动画处理，之后又进行相反的处理。 因此，该渐变中的第三种颜色会褪掉，之后再次变为不透明。
Imports Microsoft.VisualBasic
Imports System
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Input
Imports System.Windows.Media
Imports System.Windows.Media.Animation
Imports System.Windows.Shapes
Namespace BrushesIntroduction
Public Class GradientStopAnimationExample
Inherits Page
Public Sub New()
Title = "GradientStop Animation Example"
Background = Brushes.White
' Create a NameScope for the page so that
' Storyboards can be used.
NameScope.SetNameScope(Me, New NameScope())
' Create a rectangle. This rectangle will
' be painted with a gradient.
Dim aRectangle As New Rectangle()
aRectangle.Width = 200
aRectangle.Height = 100
aRectangle.Stroke = Brushes.Black
aRectangle.StrokeThickness = 1
' Create a LinearGradientBrush to paint
' the rectangle's fill.
Dim gradientBrush As New LinearGradientBrush()
' Create gradient stops for the brush.
Dim stop1 As New GradientStop(Colors.MediumBlue, 0.0)
Dim stop2 As New GradientStop(Colors.Purple, 0.5)
Dim stop3 As New GradientStop(Colors.Red, 1.0)
' Register a name for each gradient stop with the
' page so that they can be animated by a storyboard.
Me.RegisterName("GradientStop1", stop1)
Me.RegisterName("GradientStop2", stop2)
Me.RegisterName("GradientStop3", stop3)
' Add the stops to the brush.
gradientBrush.GradientStops.Add(stop1)
gradientBrush.GradientStops.Add(stop2)
gradientBrush.GradientStops.Add(stop3)
' Apply the brush to the rectangle.
aRectangle.Fill = gradientBrush
'
' Animate the first gradient stop's offset from
' 0.0 to 1.0 and then back to 0.0.
'
Dim offsetAnimation As New DoubleAnimation()
offsetAnimation.From = 0.0
offsetAnimation.To = 1.0
offsetAnimation.Duration = TimeSpan.FromSeconds(1.5)
offsetAnimation.AutoReverse = True
Storyboard.SetTargetName(offsetAnimation, "GradientStop1")
Storyboard.SetTargetProperty(offsetAnimation, New PropertyPath(GradientStop.OffsetProperty))
'
' Animate the second gradient stop's color from
' Purple to Yellow and then back to Purple.
'
Dim gradientStopColorAnimation As New ColorAnimation()
gradientStopColorAnimation.From = Colors.Purple
gradientStopColorAnimation.To = Colors.Yellow
gradientStopColorAnimation.Duration = TimeSpan.FromSeconds(1.5)
gradientStopColorAnimation.AutoReverse = True
Storyboard.SetTargetName(gradientStopColorAnimation, "GradientStop2")
Storyboard.SetTargetProperty(gradientStopColorAnimation, New PropertyPath(GradientStop.ColorProperty))
' Set the animation to begin after the first animation
' ends.
gradientStopColorAnimation.BeginTime = TimeSpan.FromSeconds(3)
'
' Animate the third gradient stop's color so
' that it becomes transparent.
'
Dim opacityAnimation As New ColorAnimation()
' Reduces the target color's alpha value by 1,
' making the color transparent.
opacityAnimation.By = Color.FromScRgb(-1.0F, 0F, 0F, 0F)
opacityAnimation.Duration = TimeSpan.FromSeconds(1.5)
opacityAnimation.AutoReverse = True
Storyboard.SetTargetName(opacityAnimation, "GradientStop3")
Storyboard.SetTargetProperty(opacityAnimation, New PropertyPath(GradientStop.ColorProperty))
' Set the animation to begin after the first two
' animations have ended.
opacityAnimation.BeginTime = TimeSpan.FromSeconds(6)
' Create a Storyboard to apply the animations.
Dim gradientStopAnimationStoryboard As New Storyboard()
gradientStopAnimationStoryboard.Children.Add(offsetAnimation)
gradientStopAnimationStoryboard.Children.Add(gradientStopColorAnimation)
gradientStopAnimationStoryboard.Children.Add(opacityAnimation)
' Begin the storyboard when the left mouse button is
' pressed over the rectangle.
AddHandler aRectangle.MouseLeftButtonDown, Sub(sender As Object, e As MouseButtonEventArgs) gradientStopAnimationStoryboard.Begin(Me)
Dim mainPanel As New StackPanel()
mainPanel.Margin = New Thickness(10)
mainPanel.Children.Add(aRectangle)
Content = mainPanel
End Sub
End Class
End Namespace
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
namespace BrushesIntroduction
{
public class GradientStopAnimationExample : Page
{
public GradientStopAnimationExample()
{
Title = "GradientStop Animation Example";
Background = Brushes.White;
// Create a NameScope for the page so that
// Storyboards can be used.
NameScope.SetNameScope(this, new NameScope());
// Create a rectangle. This rectangle will
// be painted with a gradient.
Rectangle aRectangle = new Rectangle();
aRectangle.Width = 200;
aRectangle.Height = 100;
aRectangle.Stroke = Brushes.Black;
aRectangle.StrokeThickness = 1;
// Create a LinearGradientBrush to paint
// the rectangle's fill.
LinearGradientBrush gradientBrush = new LinearGradientBrush();
// Create gradient stops for the brush.
GradientStop stop1 = new GradientStop(Colors.MediumBlue, 0.0);
GradientStop stop2 = new GradientStop(Colors.Purple, 0.5);
GradientStop stop3 = new GradientStop(Colors.Red, 1.0);
// Register a name for each gradient stop with the
// page so that they can be animated by a storyboard.
this.RegisterName("GradientStop1", stop1);
this.RegisterName("GradientStop2", stop2);
this.RegisterName("GradientStop3", stop3);
// Add the stops to the brush.
gradientBrush.GradientStops.Add(stop1);
gradientBrush.GradientStops.Add(stop2);
gradientBrush.GradientStops.Add(stop3);
// Apply the brush to the rectangle.
aRectangle.Fill = gradientBrush;
//
// Animate the first gradient stop's offset from
// 0.0 to 1.0 and then back to 0.0.
//
DoubleAnimation offsetAnimation = new DoubleAnimation();
offsetAnimation.From = 0.0;
offsetAnimation.To = 1.0;
offsetAnimation.Duration = TimeSpan.FromSeconds(1.5);
offsetAnimation.AutoReverse = true;
Storyboard.SetTargetName(offsetAnimation, "GradientStop1");
Storyboard.SetTargetProperty(offsetAnimation,
new PropertyPath(GradientStop.OffsetProperty));
//
// Animate the second gradient stop's color from
// Purple to Yellow and then back to Purple.
//
ColorAnimation gradientStopColorAnimation = new ColorAnimation();
gradientStopColorAnimation.From = Colors.Purple;
gradientStopColorAnimation.To = Colors.Yellow;
gradientStopColorAnimation.Duration = TimeSpan.FromSeconds(1.5);
gradientStopColorAnimation.AutoReverse = true;
Storyboard.SetTargetName(gradientStopColorAnimation, "GradientStop2");
Storyboard.SetTargetProperty(gradientStopColorAnimation,
new PropertyPath(GradientStop.ColorProperty));
// Set the animation to begin after the first animation
// ends.
gradientStopColorAnimation.BeginTime = TimeSpan.FromSeconds(3);
//
// Animate the third gradient stop's color so
// that it becomes transparent.
//
ColorAnimation opacityAnimation = new ColorAnimation();
// Reduces the target color's alpha value by 1,
// making the color transparent.
opacityAnimation.By = Color.FromScRgb(-1.0F, 0F, 0F, 0F);
opacityAnimation.Duration = TimeSpan.FromSeconds(1.5);
opacityAnimation.AutoReverse = true;
Storyboard.SetTargetName(opacityAnimation, "GradientStop3");
Storyboard.SetTargetProperty(opacityAnimation,
new PropertyPath(GradientStop.ColorProperty));
// Set the animation to begin after the first two
// animations have ended.
opacityAnimation.BeginTime = TimeSpan.FromSeconds(6);
// Create a Storyboard to apply the animations.
Storyboard gradientStopAnimationStoryboard = new Storyboard();
gradientStopAnimationStoryboard.Children.Add(offsetAnimation);
gradientStopAnimationStoryboard.Children.Add(gradientStopColorAnimation);
gradientStopAnimationStoryboard.Children.Add(opacityAnimation);
// Begin the storyboard when the left mouse button is
// pressed over the rectangle.
aRectangle.MouseLeftButtonDown += delegate(object sender, MouseButtonEventArgs e)
{
gradientStopAnimationStoryboard.Begin(this);
};
StackPanel mainPanel = new StackPanel();
mainPanel.Margin = new Thickness(10);
mainPanel.Children.Add(aRectangle);
Content = mainPanel;
}
}
}
<Page
xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
Title="GradientStop Animation Example"
Background="White">
<StackPanel Margin="10">
<Rectangle
Width="200"
Height="100"
Stroke="Black" StrokeThickness="1">
<Rectangle.Fill>
<LinearGradientBrush>
<GradientStop x:Name="GradientStop1" Color="MediumBlue" Offset="0.0" />
<GradientStop x:Name="GradientStop2" Color="Purple" Offset="0.5" />
<GradientStop x:Name="GradientStop3" Color="Red" Offset="1.0" />
</LinearGradientBrush>
</Rectangle.Fill>
<Rectangle.Triggers>
<EventTrigger RoutedEvent="Rectangle.MouseLeftButtonDown">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetName="GradientStop1"
Storyboard.TargetProperty="Offset"
From="0.0" To="1.0" Duration="0:0:1.5"
AutoReverse="True" />
<ColorAnimation
Storyboard.TargetName="GradientStop2"
Storyboard.TargetProperty="Color"
From="Purple" To="Yellow"
Duration="0:0:1.5"
AutoReverse="True"
BeginTime="0:0:3" />
<ColorAnimation
Storyboard.TargetName="GradientStop3"
Storyboard.TargetProperty="Color"
Duration="0:0:1.5"
AutoReverse="True"
BeginTime="0:0:6">
<ColorAnimation.By>
<Color ScA="-1" ScR="0" ScB="0" ScG="0" />
</ColorAnimation.By>
</ColorAnimation>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</Rectangle.Triggers>
</Rectangle>
</StackPanel>
</Page>
尽管本示例使用 LinearGradientBrush，但是其过程与对 RadialGradientBrush 中的 GradientStop 对象进行动画处理相同。
有关其他示例，请参见 Brushes Sample（画笔示例）。