C# WPF 动画标签内容未显示

Question

我正在尝试为标签的内容制作动画以执行以下操作：

Loading
Loading.
Loading..
Loading...

再次：

Loading
Loading.
Loading..
Loading...

诸如此类example。

代码下方：

<Label Grid.Row="2" x:Name="CurrentTask" 
       FontFamily="Microsoft Sans Serif" FontSize="18" FontStyle="Italic" FontWeight="Bold" 
       Foreground="White" Content="Loading">
    <Label.Template>
        <ControlTemplate>
            <ControlTemplate.Triggers>
                <Trigger Property="IsEnabled" Value="False">
                    <Trigger.EnterActions>
                        <BeginStoryboard>
                            <Storyboard>
                                <ObjectAnimationUsingKeyFrames Storyboard.TargetName="PART_Content" Storyboard.TargetProperty="Content" Duration="00:00:00.8" RepeatBehavior="Forever">
                                    <DiscreteObjectKeyFrame KeyTime="00:00:00.0" Value="Loading"/>
                                    <DiscreteObjectKeyFrame KeyTime="00:00:00.2" Value="Loading."/>
                                    <DiscreteObjectKeyFrame KeyTime="00:00:00.4" Value="Loading.."/>
                                    <DiscreteObjectKeyFrame KeyTime="00:00:00.6" Value="Loading..."/>
                                </ObjectAnimationUsingKeyFrames>
                            </Storyboard>
                        </BeginStoryboard>
                    </Trigger.EnterActions>
                </Trigger>
            </ControlTemplate.Triggers>
        </ControlTemplate>
    </Label.Template>
</Label>

问题是标签内容在 wpf 窗口中不可见。它没有被显示。我做错了什么？

同样在类型的行中：

<DiscreteObjectKeyFrame KeyTime="00:00:00.0" Value="Loading"/>

我想将标签内容连接到点而不是硬编码值，我该怎么做？我不想在每个DiscreteObjectKeyFrame 中重复“加载”字符串。

更新： 例如在应用标签样式的情况下，我使用了 label.loaded，而不是在 IsEnabled=True 上引发触发器：

    <Label Grid.Row="2" x:Name="CurrentTask" 
           FontFamily="Microsoft Sans Serif" FontSize="18" FontStyle="Italic"  
           Foreground="White" Content="Loading">
        <Label.Style>
            <Style TargetType="Label">
                <Style.Triggers>
                    <EventTrigger RoutedEvent="Label.Loaded">
                        <EventTrigger.Actions>
                            <BeginStoryboard>
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Content" Duration="00:00:00.8" RepeatBehavior="Forever">
                                        <DiscreteObjectKeyFrame KeyTime="00:00:00.0" Value="Loading"/>
                                        <DiscreteObjectKeyFrame KeyTime="00:00:00.2" Value="Loading."/>
                                        <DiscreteObjectKeyFrame KeyTime="00:00:00.4" Value="Loading.."/>
                                        <DiscreteObjectKeyFrame KeyTime="00:00:00.6" Value="Loading..."/>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </BeginStoryboard>
                        </EventTrigger.Actions>
                    </EventTrigger>
                </Style.Triggers>
            </Style>
        </Label.Style>
    </Label>

Answer 1

除了触发器，你的 ControlTemplate 是空的，所以显然什么都没有显示。

您可以添加 ContentPresenter，也可以删除 Storyboard.TargetName。您的 Trigger 作用于 IsEnabled 设置为 false 看起来也很奇怪。

<Label.Template>
    <ControlTemplate TargetType="Label">

        <ContentPresenter/>

        <ControlTemplate.Triggers>
            <Trigger Property="IsEnabled" Value="True">
                <Trigger.EnterActions>
                    <BeginStoryboard>
                        <Storyboard>
                            <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Content" Duration="00:00:00.8" RepeatBehavior="Forever">
                                <DiscreteObjectKeyFrame KeyTime="00:00:00.0" Value="Loading"/>
                                <DiscreteObjectKeyFrame KeyTime="00:00:00.2" Value="Loading."/>
                                <DiscreteObjectKeyFrame KeyTime="00:00:00.4" Value="Loading.."/>
                                <DiscreteObjectKeyFrame KeyTime="00:00:00.6" Value="Loading..."/>
                            </ObjectAnimationUsingKeyFrames>
                        </Storyboard>
                    </BeginStoryboard>
                </Trigger.EnterActions>
            </Trigger>
        </ControlTemplate.Triggers>
    </ControlTemplate>
</Label.Template>

但是，您实际上可能想要的是样式触发器而不是 ControlTemplate 触发器：

<Label ...>
    <Label.Style>
        <Style TargetType="Label">
            <Style.Triggers>
                <Trigger Property="IsEnabled" Value="True">
                    <Trigger.EnterActions>
                        <BeginStoryboard>
                            <Storyboard>
                                <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Content" Duration="00:00:00.8" RepeatBehavior="Forever">
                                    <DiscreteObjectKeyFrame KeyTime="00:00:00.0" Value="Loading"/>
                                    <DiscreteObjectKeyFrame KeyTime="00:00:00.2" Value="Loading."/>
                                    <DiscreteObjectKeyFrame KeyTime="00:00:00.4" Value="Loading.."/>
                                    <DiscreteObjectKeyFrame KeyTime="00:00:00.6" Value="Loading..."/>
                                </ObjectAnimationUsingKeyFrames>
                            </Storyboard>
                        </BeginStoryboard>
                    </Trigger.EnterActions>
                </Trigger>
            </Style.Triggers>
        </Style>
    </Label.Style>
</Label>

---

对于Content中重复的“Loading”字符串，只需使用两个Label，一个带有固定的“Loading”字符串，另一个带有点，并调整它们的Padding。或者更好的是，两个 TextBlock：

<StackPanel Orientation="Horizontal">
    <TextBlock Text="Loading"/>
    <TextBlock>
        <TextBlock.Style>
            <Style TargetType="TextBlock">
                <Style.Triggers>
                    <Trigger Property="IsEnabled" Value="True">
                        <Trigger.EnterActions>
                            <BeginStoryboard>
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Text" Duration="00:00:00.8" RepeatBehavior="Forever">
                                        <DiscreteObjectKeyFrame KeyTime="00:00:00.0" Value=""/>
                                        <DiscreteObjectKeyFrame KeyTime="00:00:00.2" Value="."/>
                                        <DiscreteObjectKeyFrame KeyTime="00:00:00.4" Value=".."/>
                                        <DiscreteObjectKeyFrame KeyTime="00:00:00.6" Value="..."/>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </BeginStoryboard>
                        </Trigger.EnterActions>
                    </Trigger>
                </Style.Triggers>
            </Style>
        </TextBlock.Style>
    </TextBlock>
</StackPanel>