WPF淡入淡出動畫只有一次

Question

我創建了一個淡入和淡出動畫，該動畫由viewmodel中的屬性更改觸發。 第一次淡入和淡出時此效果很好，但每次重復此操作時，僅顯示淡出，這意味着控件保持不可見，直到它閃爍到不透明度1，然后淡出。

XAML：

<DataTemplate x:Key="MessageTemplate">
    <DataTemplate.Triggers>
        <DataTrigger Binding="{Binding FadeInAnimationState}" Value="Active">
            <DataTrigger.EnterActions>
                <BeginStoryboard>
                    <Storyboard>
                        <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="Opacity">
                            <EasingDoubleKeyFrame KeyTime="0" Value="0"/>
                            <EasingDoubleKeyFrame KeyTime="0:0:0.25" Value="1"/>
                        </DoubleAnimationUsingKeyFrames>
                    </Storyboard>
                </BeginStoryboard>
            </DataTrigger.EnterActions>
        </DataTrigger>
        <DataTrigger Binding="{Binding FadeOutAnimationState}" Value="Active">
            <DataTrigger.EnterActions>
                <BeginStoryboard>
                    <Storyboard>
                        <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="Opacity">
                            <EasingDoubleKeyFrame KeyTime="0" Value="1"/>
                            <EasingDoubleKeyFrame KeyTime="0:0:1" Value="0"/>
                        </DoubleAnimationUsingKeyFrames>
                    </Storyboard>
                </BeginStoryboard>
            </DataTrigger.EnterActions>
        </DataTrigger>
    </DataTemplate.Triggers>
    <StatusBarItem>
        ...
    </StatusBarItem>
</DataTemplate>
...
<ContentPresenter ContentTemplate="{StaticResource MessageTemplate}" Content="{Binding}"/>

負責觸發動畫的Viewmodel屬性：

private DisplayState _messageState;
private DisplayState MessageState
{
    get { return _messageState; }
    set
    {
        _messageState = value;
        if (value == DisplayState.Displayed)
        {
            FadeOutAnimationState = AnimationState.Inactive;
            FadeInAnimationState = AnimationState.Active;
        }
        else
        {
            FadeInAnimationState = AnimationState.Inactive;
            FadeOutAnimationState = AnimationState.Active;
        }
    }
}

public AnimationState FadeInAnimationState
{
    ... // getter and setter with NotfiyPropertyChanged
}

public AnimationState FadeOutAnimationState
{
    ... // getter and setter with NotfiyPropertyChanged
}

和調用（調試）：

MessageState = DisplayState.Displayed;
await Task.Delay(duration);
MessageState = DisplayState.Hidden;
await Task.Delay(TimeSpan.FromSeconds(1));

我在做什么呢？

Answer 1

處理完情節提要后，您需要將其刪除。 就像是：

 <DataTrigger.EnterActions>
   <RemoveStoryboard BeginStoryboardName="FadeIn" />
   <RemoveStoryboard BeginStoryboardName="FadeOut" />       
   <BeginStoryboard Name="FadeIn">           
       <Storyboard>
          ...
       </Storyboard>
   </BeginStoryboard>
 </DataTrigger.EnterActions>

（和FadeOut ，給它起一個名字）

或者，您可以在ExitActions上執行此ExitActions ：

 <DataTrigger.EnterActions>
   <BeginStoryboard Name="FadeIn">           
       <Storyboard>
          ...
       </Storyboard>
   </BeginStoryboard>
 </DataTrigger.EnterActions>
 <DataTrigger.ExitActions>
   <RemoveStoryboard BeginStoryboardName="FadeIn" />
 </DataTrigger.ExitActions>

否則，最后一個情節提要板將保持“推送”其最后一個值，因此您不會看到任何更改