动画插入到ItemsControl

Question

我有时候发现WPF难以理解.给定以下XAML,如何添加触发器以动画(向下滑动,淡入)添加到ObservableCollection时间轴的新项目.我已经看到了列表框的各种示例,但没有项目控制.

<Grid>
    <ScrollViewer>
        <ItemsControl Name="TimelineItem"
                      ItemsSource="{Binding Timeline}"
                      Style="{StaticResource TimelineStyle}"
                      ItemContainerStyle="{StaticResource TweetItemStyle}">
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <Grid VerticalAlignment="Top"
                          HorizontalAlignment="Left">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Style="{StaticResource TweetImageColumnStyle}" />
                            <ColumnDefinition />
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition />
                            <RowDefinition />
                            <RowDefinition />
                            <RowDefinition />
                        </Grid.RowDefinitions>
                        <Rectangle Grid.Column="0"
                                   Style="{StaticResource TweetImageStyle}">
                            <Rectangle.Fill>
                                <ImageBrush ImageSource="{Binding ProfileImageUrl}" />
                            </Rectangle.Fill>
                        </Rectangle>
                        <StackPanel Grid.Column="1">
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="*" />
                                    <ColumnDefinition Width="Auto" />
                                </Grid.ColumnDefinitions>
                                <TextBlock Grid.Column="0"
                                           Style="{StaticResource TweetNameStyle}"
                                           Text="{Binding Name}" />
                                <TextBlock Grid.Column="1"
                                           Style="{StaticResource TweetTimeStyle}"
                                           Text="{Binding TimeAgo}" />
                            </Grid>
                            <Controls:TextBlockMarkup Grid.Row="1"
                                                      Grid.Column="1"
                                                      Markup="{Binding MarkupText}"
                                                      Style="{StaticResource TweetStyle}" />
                        </StackPanel>
                        <Separator Grid.Row="2"
                                   Grid.ColumnSpan="2"
                                   Style="{StaticResource TweetSeparatorTop}" />
                        <Separator Grid.Row="3"
                                   Grid.ColumnSpan="2"
                                   Style="{StaticResource TweetSeparatorBottom}" />
                    </Grid>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </ScrollViewer>
</Grid>

Answer 1

它已经有一段时间,因为我已经动画WPF,但这应该通过设置工作DataTrigger中DataTemplate的ItemsControl为Loaded事件.

几个笔记:

1. 将以下xaml添加到ItemsControl的DataTemplate中
2. <Grid>在DataTemplate中命名:"MyGrid"
3. 将一个RenderTransformOrigin属性添加到MyGrid以将Y原点设置在顶部:
   • <Grid x:Name="MyGrid" RenderTransformOrigin="0.5,0">
4. 请务必将Grid.RenderTransform附加属性包含在网格中(请参阅下面的示例)

XAML

<DataTemplate.Resources>
    <Storyboard x:Key="ItemAnimation" AutoReverse="False">
        <DoubleAnimationUsingKeyFrames Storyboard.TargetName="MyGrid" Storyboard.TargetProperty="(UIElement.Opacity)">
            <EasingDoubleKeyFrame KeyTime="0" Value="0" />
            <EasingDoubleKeyFrame KeyTime="0:0:0.5" Value="1" />
        </DoubleAnimationUsingKeyFrames>
        <DoubleAnimationUsingKeyFrames Storyboard.TargetName="MyGrid" Storyboard.TargetProperty="(UIElement.RenderTransform).(TransformGroup.Children)[0].(ScaleTransform.ScaleY)">
            <EasingDoubleKeyFrame KeyTime="0" Value="0" />
            <EasingDoubleKeyFrame KeyTime="0:0:0.5" Value="1" />
        </DoubleAnimationUsingKeyFrames>
    </Storyboard>
</DataTemplate.Resources>

<DataTemplate.Triggers>
    <EventTrigger RoutedEvent="FrameworkElement.Loaded">
        <BeginStoryboard Storyboard="{StaticResource ItemAnimation}" />
    </EventTrigger>
</DataTemplate.Triggers>

将RenderTransform组添加到网格中

<!-- Include in the Grid -->
<Grid.RenderTransform>
    <TransformGroup>
        <ScaleTransform/>
    </TransformGroup>
</Grid.RenderTransform>

这应该让你足够接近,以便你自己定制它.FWIW:我使用的混合编辑的风格打造出来的动画ItemTemplate中的Timeline对象.

最后一点:当窗口第一次加载ItemsControl时,对于原始集合中的每个项目,都会发生动画.当单个项目添加到集合中时,将会发生这种情况.这种行为有点不稳定,因此您可以删除xaml中触发器的显式绑定,并在ItemsControl或Window加载后绑定代码隐藏中的触发器.

编辑

1. 我已经更新了示例,以便它现在可以与您的XAML一起使用.
2. 添加了另一个动画来滑动(排序)新项目.实际上,它从0%的顶部开始从0%增长到100%.
3. 修改了上面的注释#3以包含RenderTransformOrigin属性.
4. 添加了注释#4以包含Grid.RenderTransform附加属性.