我不知道如何在纯 XAML 中执行两种动画（淡入和淡出）。但简单的淡出可以实现比较简单。将 DataTriggers 替换为 Triggers，并删除 ExitActions，因为它们在淡出场景中没有意义。这就是您将拥有的：
<Style TargetType="FrameworkElement" x:Key="animatedList">
<Setter Property="Visibility" Value="Hidden"/>
<Style.Triggers>
<Trigger Property="Visibility" Value="Visible">
<Trigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="Opacity"
From="0.0" To="1.0" Duration="0:0:0.2"/>
</Storyboard>
</BeginStoryboard>
</Trigger.EnterActions>
</Trigger>
</Style.Triggers>
</Style>
但是，嘿，不要放弃。如果您想支持这两种动画，我可以建议在 XAML 后面进行少量编码。当我们做了一个技巧之后，我们通过在XAML中添加一行代码就可以得到你想要的东西：
<Button Content="Fading button"
x:Name="btn"
loc:VisibilityAnimation.IsActive="True"/>
每次我们将 btn.Visibility 从“可见”更改为“隐藏/折叠”按钮时，按钮就会淡出。每次我们重新更改可见性时，按钮都会淡入。这个技巧适用于任何 FrameworkElement（包括 ListView :) ）。
这是 VisibilityAnimation.IsActive 附加属性的代码：
public class VisibilityAnimation : DependencyObject
{
private const int DURATION_MS = 200;
private static readonly Hashtable _hookedElements = new Hashtable();
public static readonly DependencyProperty IsActiveProperty =
DependencyProperty.RegisterAttached("IsActive",
typeof(bool),
typeof(VisibilityAnimation),
new FrameworkPropertyMetadata(false, new PropertyChangedCallback(OnIsActivePropertyChanged)));
public static bool GetIsActive(UIElement element)
{
if (element == null)
{
throw new ArgumentNullException("element");
}
return (bool)element.GetValue(IsActiveProperty);
}
public static void SetIsActive(UIElement element, bool value)
{
if (element == null)
{
throw new ArgumentNullException("element");
}
element.SetValue(IsActiveProperty, value);
}
static VisibilityAnimation()
{
UIElement.VisibilityProperty.AddOwner(typeof(FrameworkElement),
new FrameworkPropertyMetadata(Visibility.Visible, new PropertyChangedCallback(VisibilityChanged), CoerceVisibility));
}
private static void VisibilityChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// So what? Ignore.
}
private static void OnIsActivePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var fe = d as FrameworkElement;
if (fe == null)
{
return;
}
if (GetIsActive(fe))
{
HookVisibilityChanges(fe);
}
else
{
UnHookVisibilityChanges(fe);
}
}
private static void UnHookVisibilityChanges(FrameworkElement fe)
{
if (_hookedElements.Contains(fe))
{
_hookedElements.Remove(fe);
}
}
private static void HookVisibilityChanges(FrameworkElement fe)
{
_hookedElements.Add(fe, false);
}
private static object CoerceVisibility(DependencyObject d, object baseValue)
{
var fe = d as FrameworkElement;
if (fe == null)
{
return baseValue;
}
if (CheckAndUpdateAnimationStartedFlag(fe))
{
return baseValue;
}
// If we get here, it means we have to start fade in or fade out
// animation. In any case return value of this method will be
// Visibility.Visible.
var visibility = (Visibility)baseValue;
var da = new DoubleAnimation
{
Duration = new Duration(TimeSpan.FromMilliseconds(DURATION_MS))
};
da.Completed += (o, e) =>
{
// This will trigger value coercion again
// but CheckAndUpdateAnimationStartedFlag() function will reture true
// this time, and animation will not be triggered.
fe.Visibility = visibility;
// NB: Small problem here. This may and probably will brake
// binding to visibility property.
};
if (visibility == Visibility.Collapsed || visibility == Visibility.Hidden)
{
da.From = 1.0;
da.To = 0.0;
}
else
{
da.From = 0.0;
da.To = 1.0;
}
fe.BeginAnimation(UIElement.OpacityProperty, da);
return Visibility.Visible;
}
private static bool CheckAndUpdateAnimationStartedFlag(FrameworkElement fe)
{
var hookedElement = _hookedElements.Contains(fe);
if (!hookedElement)
{
return true; // don't need to animate unhooked elements.
}
var animationStarted = (bool) _hookedElements[fe];
_hookedElements[fe] = !animationStarted;
return animationStarted;
}
}
这里最重要的是 CoerceVisibility() 方法。正如您所看到的，在淡入淡出动画完成之前，我们不允许更改此属性。
这段代码既不是线程安全的，也不是没有错误的。它的唯一目的是表明方向:)。因此，请随意改进、编辑并获得声誉；）。
