我正在使用flipview并绑定数据。我想在更改主题时使用fadein / out动画。我正在使用DispatcherTimer来更改它（_timer.Tick + = ChangeImage;）。
将数据绑定到flipview
<FlipView x:Name="TheFlipView"
ItemsSource="{Binding Source={StaticResource itemsViewSource}}"
ItemTemplate="{StaticResource Standard250x250ItemTemplate}"/>
改变功能。
private void ChangeItems(object sender, object o)
{
var totalItems = TheFlipView.Items.Count;
var newItemIndex = (TheFlipView.SelectedIndex + 1) % totalItems;
TheFlipView.SelectedIndex = newItemIndex;
}
我尝试过Storyboard和FadeInThemeAnimation类，但我不能......
你能帮帮我吗？
答案 0 :(得分：3)
这是WinRT XAML Toolkit中的一个类，您可以使用myFlipView.FadeOut()之类的简单调用来淡入/淡出。您可以将代码更改为以下内容：
private async void ChangeItems(object sender, object o)
{
var totalItems = TheFlipView.Items.Count;
var newItemIndex = (TheFlipView.SelectedIndex + 1) % totalItems;
await TheFlipView.FadeOut();
TheFlipView.SelectedIndex = newItemIndex;
TheFlipView.FadeIn();
}
扩展程序类：
public static class UIElementAnimationExtensions
{
#region AttachedFadeStoryboard
/// <summary>
/// AttachedFadeStoryboard Attached Dependency Property
/// </summary>
public static readonly DependencyProperty AttachedFadeStoryboardProperty =
DependencyProperty.RegisterAttached(
"AttachedFadeStoryboard",
typeof(Storyboard),
typeof(UIElementAnimationExtensions),
new PropertyMetadata(null, OnAttachedFadeStoryboardChanged));
/// <summary>
/// Gets the AttachedFadeStoryboard property. This dependency property
/// indicates the currently running custom fade in/out storyboard.
/// </summary>
private static Storyboard GetAttachedFadeStoryboard(DependencyObject d)
{
return (Storyboard)d.GetValue(AttachedFadeStoryboardProperty);
}
/// <summary>
/// Sets the AttachedFadeStoryboard property. This dependency property
/// indicates the currently running custom fade in/out storyboard.
/// </summary>
private static void SetAttachedFadeStoryboard(DependencyObject d, Storyboard value)
{
d.SetValue(AttachedFadeStoryboardProperty, value);
}
/// <summary>
/// Handles changes to the AttachedFadeStoryboard property.
/// </summary>
/// <param name="d">
/// The <see cref="DependencyObject"/> on which
/// the property has changed value.
/// </param>
/// <param name="e">
/// Event data that is issued by any event that
/// tracks changes to the effective value of this property.
/// </param>
private static void OnAttachedFadeStoryboardChanged(
DependencyObject d, DependencyPropertyChangedEventArgs e)
{
Storyboard oldAttachedFadeStoryboard = (Storyboard)e.OldValue;
Storyboard newAttachedFadeStoryboard = (Storyboard)d.GetValue(AttachedFadeStoryboardProperty);
}
#endregion
#region FadeIn()
/// <summary>
/// Fades the element in using the FadeInThemeAnimation.
/// </summary>
/// <remarks>
/// Opacity property of the element is not affected.<br/>
/// The duration of the visible animation itself is not affected by the duration parameter. It merely indicates how long the Storyboard will run.<br/>
/// If FadeOutThemeAnimation was not used on the element before - nothing will happen.<br/>
/// </remarks>
/// <param name="element"></param>
/// <param name="duration"></param>
/// <returns></returns>
public static async Task FadeIn(this UIElement element, TimeSpan? duration = null)
{
((FrameworkElement)element).Visibility = Visibility.Visible;
var fadeInStoryboard = new Storyboard();
var fadeInAnimation = new FadeInThemeAnimation();
if (duration != null)
{
fadeInAnimation.Duration = duration.Value;
}
Storyboard.SetTarget(fadeInAnimation, element);
fadeInStoryboard.Children.Add(fadeInAnimation);
await fadeInStoryboard.BeginAsync();
}
#endregion
#region FadeOut()
/// <summary>
/// Fades the element out using the FadeOutThemeAnimation.
/// </summary>
/// <remarks>
/// Opacity property of the element is not affected.<br/>
/// The duration of the visible animation itself is not affected by the duration parameter. It merely indicates how long the Storyboard will run.<br/>
/// If FadeOutThemeAnimation was already run before and FadeInThemeAnimation was not run after that - nothing will happen.<br/>
/// </remarks>
/// <param name="element"></param>
/// <param name="duration"></param>
/// <returns></returns>
public static async Task FadeOut(this UIElement element, TimeSpan? duration = null)
{
var fadeOutStoryboard = new Storyboard();
var fadeOutAnimation = new FadeOutThemeAnimation();
if (duration != null)
{
fadeOutAnimation.Duration = duration.Value;
}
Storyboard.SetTarget(fadeOutAnimation, element);
fadeOutStoryboard.Children.Add(fadeOutAnimation);
await fadeOutStoryboard.BeginAsync();
}
#endregion
#region FadeInCustom()
/// <summary>
/// Fades the element in using a custom DoubleAnimation of the Opacity property.
/// </summary>
/// <param name="element"></param>
/// <param name="duration"></param>
/// <param name="easingFunction"> </param>
/// <returns></returns>
public static async Task FadeInCustom(this UIElement element, TimeSpan? duration = null, EasingFunctionBase easingFunction = null, double targetOpacity = 1.0)
{
CleanUpPreviousFadeStoryboard(element);
var fadeInStoryboard = new Storyboard();
var fadeInAnimation = new DoubleAnimation();
if (duration == null)
duration = TimeSpan.FromSeconds(0.4);
fadeInAnimation.Duration = duration.Value;
fadeInAnimation.To = targetOpacity;
fadeInAnimation.EasingFunction = easingFunction;
Storyboard.SetTarget(fadeInAnimation, element);
Storyboard.SetTargetProperty(fadeInAnimation, "Opacity");
fadeInStoryboard.Children.Add(fadeInAnimation);
SetAttachedFadeStoryboard(element, fadeInStoryboard);
await fadeInStoryboard.BeginAsync();
element.Opacity = targetOpacity;
fadeInStoryboard.Stop();
}
#endregion
#region FadeOutCustom()
/// <summary>
/// Fades the element out using a custom DoubleAnimation of the Opacity property.
/// </summary>
/// <param name="element"></param>
/// <param name="duration"></param>
/// <param name="easingFunction"> </param>
/// <returns></returns>
public static async Task FadeOutCustom(this UIElement element, TimeSpan? duration = null, EasingFunctionBase easingFunction = null)
{
CleanUpPreviousFadeStoryboard(element);
var fadeOutStoryboard = new Storyboard();
var fadeOutAnimation = new DoubleAnimation();
if (duration == null)
duration = TimeSpan.FromSeconds(0.4);
fadeOutAnimation.Duration = duration.Value;
fadeOutAnimation.To = 0.0;
fadeOutAnimation.EasingFunction = easingFunction;
Storyboard.SetTarget(fadeOutAnimation, element);
Storyboard.SetTargetProperty(fadeOutAnimation, "Opacity");
fadeOutStoryboard.Children.Add(fadeOutAnimation);
SetAttachedFadeStoryboard(element, fadeOutStoryboard);
await fadeOutStoryboard.BeginAsync();
element.Opacity = 0.0;
fadeOutStoryboard.Stop();
}
#endregion
#region CleanUpPreviousFadeStoryboard()
public static void CleanUpPreviousFadeStoryboard(this UIElement element)
{
var attachedFadeStoryboard = GetAttachedFadeStoryboard(element);
if (attachedFadeStoryboard != null)
{
attachedFadeStoryboard.Stop();
}
}
#endregion
}
答案 1 :(得分：0)
这个答案的目的是补充Filip Skakun的答案，因为错过了BeginAsync分机。将此扩展程序如下所示嵌入到class UIElementAnimationExtensions后，它适用于我的情况。 ^ _ ^
public async static Task BeginAsync(this Storyboard myStoryboard)
{
SemaphoreSlim signal = new SemaphoreSlim(0, 1);
EventHandler<object> eventHandler = new EventHandler<object>(
(sender, args) =>
{
signal.Release();
}
);
myStoryboard.Completed += eventHandler;
myStoryboard.Begin();
await signal.WaitAsync();
myStoryboard.Completed -= eventHandler;
}
顺便说一句，此扩展的概念基于Is it possible to await an event instead of another async method?的答案。