当左边距变为负值时,动画减慢

Question

我试图让一个多边形完全从屏幕左侧移动,穿过屏幕,然后完全离开屏幕右侧,然后再返回.

我已经开始工作了.但是,出于某种原因,只要左边距变为负值,动画就会突然减慢.一旦左边距变为正,它就会再次加速.

为什么会这样？我怎么能阻止它？

这是完整的代码,用于演示:

<Window x:Class="Geometry.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <PathGeometry x:Key="MyGeometry">
            <PathGeometry.Figures>
                <PathFigure>
                    <PathFigure.Segments>
                        <LineSegment Point="0.30,0" />
                        <LineSegment Point="0.70,1" />
                        <LineSegment Point="0.40,1" />
                        <LineSegment Point="0,0" />
                    </PathFigure.Segments>
                </PathFigure>
            </PathGeometry.Figures>
        </PathGeometry>
        <Storyboard x:Key="MovingAnimation">
            <ThicknessAnimationUsingKeyFrames RepeatBehavior="1:0:0" FillBehavior="HoldEnd" Storyboard.TargetName="_path" Storyboard.TargetProperty="Margin" >
                <DiscreteThicknessKeyFrame KeyTime="0:0:0" Value="-2.0,0,0,0"  />
                <LinearThicknessKeyFrame KeyTime="0:0:10" Value="1.0,0,0,0"  />
                <LinearThicknessKeyFrame KeyTime="0:0:20" Value="-2.0,0,0,0"  />
            </ThicknessAnimationUsingKeyFrames>
        </Storyboard>
    </Window.Resources>
    <Window.Triggers>
        <EventTrigger RoutedEvent="Window.Loaded">
            <BeginStoryboard Storyboard="{StaticResource MovingAnimation}" ></BeginStoryboard>
        </EventTrigger>
    </Window.Triggers>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <StackPanel Grid.Row="0" Orientation="Horizontal">
            <Label>Margin:</Label>
            <TextBlock Text="{Binding ElementName=_path, Path=Margin.Left, StringFormat={}{0:0.#}}" />
        </StackPanel>
    <Canvas Name="_canvas" Grid.Row="1">
        <Border Margin="0" Width="1" Height="1" VerticalAlignment="Center" HorizontalAlignment="Center">
            <Border.RenderTransform>
                <ScaleTransform 
                    ScaleX="{Binding ElementName=_canvas, Path=ActualWidth}" 
                    ScaleY="{Binding ElementName=_canvas, Path=ActualHeight}"
                    CenterX="0"
                    CenterY="0">
                </ScaleTransform>
            </Border.RenderTransform>
            <Path 
                Name="_path" 
                Fill="#CCCCFF" 
                Data="{StaticResource MyGeometry}" 
                Width="1.0" 
                Height="1.0" 
                >
        </Path>
        </Border>
    </Canvas>
    </Grid>
</Window>

Answer 1

动画Margin属性将触发额外的测量/排列过程，这反过来会导致更多的性能影响（尽管在本例中可能不明显）。另一方面，“仅渲染”属性的动画不会触发布局重新排列，因此性能更加友好。

请看一下更简单的方法来完成我想您想要得到的事情：

<Window x:Class="Geometry.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="518" Width="530">
<Window.Resources>
    <PathGeometry x:Key="MyGeometry">
        <PathGeometry.Figures>
            <PathFigure>
                <PathFigure.Segments>
                    <LineSegment Point="0.30,0" />
                    <LineSegment Point="0.70,1" />
                    <LineSegment Point="0.40,1" />
                    <LineSegment Point="0,0" />
                </PathFigure.Segments>
            </PathFigure>
        </PathGeometry.Figures>
    </PathGeometry>
    <Storyboard x:Key="MovingAnimation">
        <DoubleAnimationUsingKeyFrames RepeatBehavior="1:0:0" FillBehavior="HoldEnd" Storyboard.TargetName="_scaleTransform" Storyboard.TargetProperty="CenterX" >
            <LinearDoubleKeyFrame KeyTime="0:0:0" Value="1.2" />
            <LinearDoubleKeyFrame KeyTime="0:0:10" Value="-0.5" />
            <LinearDoubleKeyFrame KeyTime="0:0:20" Value="1.2" />
        </DoubleAnimationUsingKeyFrames>
    </Storyboard>
</Window.Resources>
<Window.Triggers>
    <EventTrigger RoutedEvent="Window.Loaded">
        <BeginStoryboard Storyboard="{StaticResource MovingAnimation}" ></BeginStoryboard>
    </EventTrigger>
</Window.Triggers>
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <StackPanel Grid.Row="0" Orientation="Horizontal">
        <Label>Margin:</Label>
        <TextBlock Text="{Binding ElementName=_scaleTransform, Path=CenterX, StringFormat={}{0:0.#}}" VerticalAlignment="Center" />
    </StackPanel>
<!--
    <Border Grid.Row="1" Margin="150" BorderBrush="Red" BorderThickness="1">
-->
    <Grid Name="_canvas" Grid.Row="1">
        <Path Name="_path" Fill="#CCCCFF" Data="{StaticResource MyGeometry}" 
              Width="1.0"
              Height="1.0"
              HorizontalAlignment="Center"
              VerticalAlignment="Center">
            <Path.RenderTransform>
                <ScaleTransform x:Name="_scaleTransform"
                    ScaleX="{Binding ElementName=_canvas, Path=ActualWidth}" 
                    ScaleY="{Binding ElementName=_canvas, Path=ActualHeight}"
                    CenterX="1.2"
                    CenterY="0.5">
                </ScaleTransform>
            </Path.RenderTransform>
        </Path>
    </Grid>
<!--
    </Border>
-->
</Grid>
</Window>