ControlTemplate中嵌套的ScrollViewer ScrollChanged

Question

我有一个与ControlTemplate绑定的ScrollViewer(工作正常)，内部有一个Grid(覆盖默认的ScrollViewer并将ScrollBar设置在内容上方)，最后我有一些EventTrigger，它将Storyboard中ScrollBar的不透明度设置为1或0。它们也工作正常。

我缺少的是其中一个触发器，它将Opacity设置为1，以防发生滚动。它可以通过鼠标、鼠标滚轮、手写笔或触摸进行滚动，因此最好采用ScrollViewer的ScrollChanged或ScrollBar本身的Scroll。但我无法让它发挥作用。哦，顺便说一句，我不能改变它的建造方式。因此，我必须在ControlTemplate中使用纯XAML来制作它(我知道如何使用代码来制作它，但这在这里是不可能的)。

样式看起来是这样的：

<Style TargetType="{x:Type controls:ViewerControl}">
// ... some properties of no interest here
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type controls:ViewerControl}">
<Border Grid.Row="0" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto" Name="PART_ScrollViewer">
<ScrollViewer.Template>
<ControlTemplate TargetType="{x:Type ScrollViewer}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.Triggers>
<EventTrigger RoutedEvent="Grid.Loaded">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Duration="00:00:02" From="1" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_VerticalScrollBar"/>
<DoubleAnimation Duration="00:00:02" From="1" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_HorizontalScrollBar"/>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
<EventTrigger RoutedEvent="Grid.MouseEnter">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Duration="0" From="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_VerticalScrollBar"/>
<DoubleAnimation Duration="0" From="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_HorizontalScrollBar"/>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
<EventTrigger RoutedEvent="Grid.MouseLeave">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Duration="00:00:02" From="1" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_VerticalScrollBar"/>
<DoubleAnimation Duration="00:00:02" From="1" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_HorizontalScrollBar"/>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</Grid.Triggers>
<ScrollContentPresenter Grid.ColumnSpan="2"
Grid.RowSpan="2"
ContentTemplate="{TemplateBinding ContentTemplate}"
Content="{TemplateBinding Content}"/>
<ScrollBar Name="PART_VerticalScrollBar"
HorizontalAlignment="Right"
Opacity="0"
Grid.Column="1"
IsTabStop="False"
Value="{TemplateBinding VerticalOffset}"
Maximum="{TemplateBinding ScrollableHeight}"
ViewportSize="{TemplateBinding ViewportHeight}"
Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}"/>
<ScrollBar Name="PART_HorizontalScrollBar"
VerticalAlignment="Bottom"
Orientation="Horizontal"
Opacity="0"
Grid.Row="1"
IsTabStop="False"
Value="{TemplateBinding HorizontalOffset}"
Maximum="{TemplateBinding ScrollableWidth}"
ViewportSize="{TemplateBinding ViewportWidth}"
Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}"/>
</Grid>
</ControlTemplate>
</ScrollViewer.Template>
<StackPanel IsItemsHost="True" Name="PART_ItemsHost" VerticalAlignment="Center" HorizontalAlignment="Center"/>
</ScrollViewer>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

我试过这样的东西：

<ScrollViewer.Triggers>
<EventTrigger RoutedEvent="ScrollViewer.ScrollChanged">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Duration="0" From="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_VerticalScrollBar"/>
<DoubleAnimation Duration="0" From="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_HorizontalScrollBar"/>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</ScrollViewer.Triggers>

但是，如果我把它直接放在ScrollViewer中，它就找不到ScrollBars，如果我将它放在Grid中，它就会被完全忽略(Grid本身对ScrollViewer没有控制权，似乎不会把它夸大

我发现了一个答案，有人使用了VisualStateManager，但这似乎只在Silverlight中有效，而在C#中无效。它看起来是这样的：

<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="ScrollStates">
<VisualStateGroup.Transitions>
<VisualTransition GeneratedDuration="00:00:00.5"/>
</VisualStateGroup.Transitions>
<VisualState x:Name="Scrolling">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_VerticalScrollBar"/>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_HorizontalScrollBar"/>
</Storyboard>
</VisualState>
<VisualState x:Name="NotScrolling"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>

有人知道怎么做吗？

Answer 1

我的一位同事找到了答案：

<ControlTemplate.Triggers>
<EventTrigger RoutedEvent="ScrollViewer.ScrollChanged">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Duration="0" From="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_VerticalScrollBar"/>
<DoubleAnimation Duration="0" From="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_HorizontalScrollBar"/>
<DoubleAnimation BeginTime="00:00:02" Duration="00:00:01.5" From="1" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_VerticalScrollBar"/>
<DoubleAnimation BeginTime="00:00:02" Duration="00:00:01.5" From="1" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PART_HorizontalScrollBar"/>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</ControlTemplate.Triggers>

所以如果你把EventTrigger放在ControlTemplate.Triggers里面，它就像一个符咒。。。真的很酷。您只需将这些MouseEnter和MouseLeave放在ScrollBars内，否则，如果光标输入ScrollViewer的内容，它们也会被触发，而不仅仅是在输入ScrollBars时。