实现“下滑” WPF 中的动画

Question

我正在尝试为 Expander 控件创建自己的模板。当控件展开时，我希望内容慢慢地向下滑动。

内容所需的高度在编译时未知。

我以为我们可以将向下滑动定义为动画：

<Storyboard x:Key="ExpandContent">

    <DoubleAnimation 
        Storyboard.TargetName="_expanderContent" 
        Storyboard.TargetProperty="Height" 
        From="0.0" 
        To="{Binding ElementName=_expanderContent,Path=DesiredHeight}"
        Duration="0:0:1.0" />
</Storyboard>

但不幸的是不是。我们得到一个错误

无法冻结此情节提要时间线树以供跨线程使用。

看来我们在定义动画参数时不能使用绑定。 （也在这个问题中讨论过.)

有谁对我如何解决这个问题有任何想法吗？我对使用 LayoutTransform.ScaleY 持谨慎态度，因为这会产生扭曲的图像。

这类似于 这个问题，但是这个问题的答案涉及编写隐藏代码，我认为这在控件模板中是不可能的。 我想知道是否可以实现基于 XAML 的解决方案。

---

For what it's worth, here is the current state of my control template.

<ControlTemplate x:Key="ExpanderControlTemplate"  TargetType="{x:Type Expander}">
    <ControlTemplate.Resources>
            <!-- Here are the storyboards which don't work -->
            <Storyboard x:Key="ExpandContent">

                <DoubleAnimation 
                    Storyboard.TargetName="_expanderContent" 
                    Storyboard.TargetProperty="Height" 
                    From="0.0" 
                    To="{Binding ElementName=_expanderContent,Path=DesiredHeight}"
                    Duration="0:0:1.0" />
            </Storyboard>
            <Storyboard x:Key="ContractContent">

                <DoubleAnimation 
                    Storyboard.TargetName="_expanderContent" 
                    Storyboard.TargetProperty="Height" 
                    From="{Binding ElementName=_expanderContent,Path=DesiredHeight}"
                    To="0.0"
                    Duration="0:0:1.0" />

            </Storyboard>
        </ControlTemplate.Resources>
    <Grid Name="MainGrid" Background="White">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Name="ContentRow" Height="Auto" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Border>
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="Auto" />
                </Grid.ColumnDefinitions>
                <ContentPresenter ContentSource="Header" />
                <ToggleButton Template="{StaticResource ProductButtonExpand}"
                              Grid.Column="1"
                              IsChecked="{Binding Path=IsExpanded,Mode=TwoWay,RelativeSource={RelativeSource TemplatedParent}}" 
                              />
                <Rectangle Grid.ColumnSpan="2" Fill="#FFDADADA" Height="1" Margin="8,0,8,2" VerticalAlignment="Bottom"/>

            </Grid>
        </Border>

            <ContentPresenter Grid.Row="1" HorizontalAlignment="Stretch" Name="_expanderContent">

            </ContentPresenter>

    </Grid>
    <ControlTemplate.Triggers>
        <Trigger Property="IsExpanded" Value="True">
            <Setter TargetName="_expanderContent" Property="Height" Value="{Binding ElementName=_expanderContent,Path=DesiredHeight}" />

                <!-- Here is where I would activate the storyboard if they did work -->
                <Trigger.EnterActions>
                <!--<BeginStoryboard Storyboard="{StaticResource ExpandContent}"/>-->
            </Trigger.EnterActions>
                <Trigger.ExitActions>
                    <!--<BeginStoryboard x:Name="ContractContent_BeginStoryboard" Storyboard="{StaticResource ContractContent}"/>-->
                </Trigger.ExitActions>
        </Trigger>
            <Trigger Property="IsExpanded" Value="False">

                <Setter TargetName="_expanderContent" Property="Height" Value="0" />
            </Trigger>
        </ControlTemplate.Triggers>

</ControlTemplate>

Answer 1

这是一个老问题，但我今天遇到了问题，所以我想发布我的解决方案是值得的：

我必须对网格行的 Height 属性进行动画处理（上下滑动），但需要动态绑定，以便该行将再次滑动到与之前相同的位置。

我发现这个答案非常有帮助（在与 XAML 进行无果的斗争之后）：
http://go4answers.webhost4life.com/Question/ found-solution-work-protected-override-190845.aspx

有时，在代码隐藏中执行操作会更简单

        Storyboard sb = new Storyboard();

        var animation = new GridLengthAnimation
        {
                Duration = new Duration(500.Milliseconds()),
                From = this.myGridRow.Height,
                To = new GridLength(IsGridRowVisible ? GridRowPreviousHeight : 0, GridUnitType.Pixel)
        };

        // Set the target of the animation
        Storyboard.SetTarget(animation, this.myGridRow);
        Storyboard.SetTargetProperty(animation, new PropertyPath("Height"));
        
        // Kick the animation off
        sb.Children.Add(animation);
        sb.Begin();

： GridLengthAnimation 类可以在这里找到：
http://social.msdn.microsoft.com/forums/en-US/wpf/thread/da47a4b8-4d39-4d6e-a570-7dbe51a842e4/

/// <summary>
    /// Animates a grid length value just like the DoubleAnimation animates a double value
    /// </summary>
    public class GridLengthAnimation : AnimationTimeline
    {
        /// <summary>
        /// Returns the type of object to animate
        /// </summary>
        public override Type TargetPropertyType
        {
            get
            {
                return typeof(GridLength);
            }
        }

        /// <summary>
        /// Creates an instance of the animation object
        /// </summary>
        /// <returns>Returns the instance of the GridLengthAnimation</returns>
        protected override System.Windows.Freezable CreateInstanceCore()
        {
            return new GridLengthAnimation();
        }

        /// <summary>
        /// Dependency property for the From property
        /// </summary>
        public static readonly DependencyProperty FromProperty = DependencyProperty.Register("From", typeof(GridLength),
                typeof(GridLengthAnimation));

        /// <summary>
        /// CLR Wrapper for the From depenendency property
        /// </summary>
        public GridLength From
        {
            get
            {
                return (GridLength)GetValue(GridLengthAnimation.FromProperty);
            }
            set
            {
                SetValue(GridLengthAnimation.FromProperty, value);
            }
        }

        /// <summary>
        /// Dependency property for the To property
        /// </summary>
        public static readonly DependencyProperty ToProperty = DependencyProperty.Register("To", typeof(GridLength),
                typeof(GridLengthAnimation));

        /// <summary>
        /// CLR Wrapper for the To property
        /// </summary>
        public GridLength To
        {
            get
            {
                return (GridLength)GetValue(GridLengthAnimation.ToProperty);
            }
            set
            {
                SetValue(GridLengthAnimation.ToProperty, value);
            }
        }

        /// <summary>
        /// Animates the grid let set
        /// </summary>
        /// <param name="defaultOriginValue">The original value to animate</param>
        /// <param name="defaultDestinationValue">The final value</param>
        /// <param name="animationClock">The animation clock (timer)</param>
        /// <returns>Returns the new grid length to set</returns>
        public override object GetCurrentValue(object defaultOriginValue,
            object defaultDestinationValue, AnimationClock animationClock)
        {
            double fromVal = ((GridLength)GetValue(GridLengthAnimation.FromProperty)).Value;
            //check that from was set from the caller
            if (fromVal == 1)
                //set the from as the actual value
                fromVal = ((GridLength)defaultDestinationValue).Value;

            double toVal = ((GridLength)GetValue(GridLengthAnimation.ToProperty)).Value;

            if (fromVal > toVal)
                return new GridLength((1 - animationClock.CurrentProgress.Value) * (fromVal - toVal) + toVal, GridUnitType.Star);
            else
                return new GridLength(animationClock.CurrentProgress.Value * (toVal - fromVal) + fromVal, GridUnitType.Star);
        }
    }

Answer 2

如果您可以将Interactions与FluidLayout一起使用（Blend 4 SDK）你很幸运，它对于那些精美的动画非常有用。

首先将内容 CP 的高度设置为 0：

<ContentPresenter Grid.Row="1"
    HorizontalAlignment="Stretch"
    x:Name="_expanderContent"
    Height="0"/>

要对其进行动画处理，只需在表示展开的 VisualState 中将 Height 动画设置为 NaN状态（非离散动画不允许您使用 NaN）：

xmlns:is="http://schemas.microsoft.com/expression/2010/interactions"

<Grid x:Name="MainGrid" Background="White">
    <VisualStateManager.CustomVisualStateManager>
        <is:ExtendedVisualStateManager/>
    </VisualStateManager.CustomVisualStateManager>
    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup x:Name="ExpansionStates" is:ExtendedVisualStateManager.UseFluidLayout="True">
            <VisualStateGroup.Transitions>
                <VisualTransition GeneratedDuration="0:0:1"/>
            </VisualStateGroup.Transitions>
            <VisualState x:Name="Expanded">
                <Storyboard>
                    <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.Height)"
                                                   Storyboard.TargetName="_expanderContent">
                        <DiscreteDoubleKeyFrame KeyTime="0" Value="NaN"/>
                    </DoubleAnimationUsingKeyFrames>
                </Storyboard>
            </VisualState>
            <VisualState x:Name="Collapsed"/>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>
    <!-- ... --->

这应该是所有必需的，流体布局将从那里为您创建过渡。

---

如果您有一个代码隐藏解决方案就可以了，您甚至可以在字典中使用代码隐藏，如下所示：

<!-- TestDictionary.xaml -->
<ResourceDictionary x:Class="Test.TestDictionary"
                    ...>

//TestDictionary.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;

namespace Test
{
    partial class TestDictionary : ResourceDictionary
    {
        //Handlers and such here
    }
}

Answer 3

CodeProject 上有一个现成的纯 XAML 解决方案：

样式：

    <local:MultiplyConverter x:Key="MultiplyConverter" />
    <Style TargetType="Expander" x:Key="VerticalSlidingEmptyExpander">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Expander}">
                    <ScrollViewer x:Name="ExpanderContentScrollView"
                  HorizontalScrollBarVisibility="Hidden"
                  VerticalScrollBarVisibility="Hidden"
                  HorizontalContentAlignment="Stretch"
                  VerticalContentAlignment="Top"
                  >
                        <ScrollViewer.Tag>
                            <system:Double>0.0</system:Double>
                        </ScrollViewer.Tag>
                        <ScrollViewer.Height>
                            <MultiBinding Converter="{StaticResource MultiplyConverter}">
                                <Binding Path="ActualHeight" ElementName="ExpanderContent"/>
                                <Binding Path="Tag" RelativeSource="{RelativeSource Self}" />
                            </MultiBinding>
                        </ScrollViewer.Height>
                        <ContentPresenter x:Name="ExpanderContent" ContentSource="Content"/>
                    </ScrollViewer>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsExpanded" Value="True">
                            <Trigger.EnterActions>
                                <BeginStoryboard>
                                    <Storyboard>
                                        <DoubleAnimation 
                       Storyboard.TargetName="ExpanderContentScrollView"
                       Storyboard.TargetProperty="Tag"
                       To="1"
                       Duration="0:0:0.2"/>
                                    </Storyboard>
                                </BeginStoryboard>
                            </Trigger.EnterActions>
                            <Trigger.ExitActions>
                                <BeginStoryboard>
                                    <Storyboard>
                                        <DoubleAnimation 
                         Storyboard.TargetName="ExpanderContentScrollView"
                         Storyboard.TargetProperty="Tag"
                         To="0"
                         Duration="0:0:0.2"/>
                                    </Storyboard>
                                </BeginStoryboard>
                            </Trigger.ExitActions>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style TargetType="Expander" x:Key="HorizontalSlidingEmptyExpander">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Expander}">
                    <ScrollViewer x:Name="ExpanderContentScrollView"
                  HorizontalScrollBarVisibility="Hidden"
                  VerticalScrollBarVisibility="Hidden"
                  HorizontalContentAlignment="Left"
                  VerticalContentAlignment="Stretch"
                  >
                        <ScrollViewer.Tag>
                            <system:Double>0.0</system:Double>
                        </ScrollViewer.Tag>
                        <ScrollViewer.Width>
                            <MultiBinding Converter="{StaticResource MultiplyConverter}">
                                <Binding Path="ActualWidth" ElementName="ExpanderContent"/>
                                <Binding Path="Tag" RelativeSource="{RelativeSource Self}" />
                            </MultiBinding>
                        </ScrollViewer.Width>
                        <ContentPresenter x:Name="ExpanderContent" ContentSource="Content"/>
                    </ScrollViewer>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsExpanded" Value="True">
                            <Trigger.EnterActions>
                                <BeginStoryboard>
                                    <Storyboard>
                                        <DoubleAnimation 
                       Storyboard.TargetName="ExpanderContentScrollView"
                       Storyboard.TargetProperty="Tag"
                       To="1"
                       Duration="0:0:0.2"/>
                                    </Storyboard>
                                </BeginStoryboard>
                            </Trigger.EnterActions>
                            <Trigger.ExitActions>
                                <BeginStoryboard>
                                    <Storyboard>
                                        <DoubleAnimation 
                         Storyboard.TargetName="ExpanderContentScrollView"
                         Storyboard.TargetProperty="Tag"
                         To="0"
                         Duration="0:0:0.2"/>
                                    </Storyboard>
                                </BeginStoryboard>
                            </Trigger.ExitActions>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

MultiplyConverter：

public class MultiplyConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType,
           object parameter, CultureInfo culture)
    {
        double result = 1.0;
        for (int i = 0; i < values.Length; i++)
        {
            if (values[i] is double)
                result *= (double)values[i];
        }

        return result;
    }

    public object[] ConvertBack(object value, Type[] targetTypes,
           object parameter, CultureInfo culture)
    {
        throw new Exception("Not implemented");
    }
}

我复制了样式以具有水平和垂直版本，并省略了切换按钮，但您可以轻松地从原始帖子中获取它。