Fading out a wpf window on close

问题:

I want to fade a window in/out in my application.
Fading in occurs on Window.Loaded and I wanted to fade out on close (Window.Closed or Window.Closing). Fading in works perfectly, but Window.Closing is not allowed value for RoutedEvent property.
What RoutedEvent should I be using for Close?

    <Window.Triggers>
        <EventTrigger RoutedEvent="Window.Loaded">
            <BeginStoryboard>
                <Storyboard>
                    <DoubleAnimation Storyboard.TargetProperty="Opacity" From="0" To="1" Duration="0:0:2" FillBehavior="HoldEnd" />
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
        <EventTrigger RoutedEvent="Window.Closing">
            <BeginStoryboard>
                <Storyboard>
                    <DoubleAnimation Storyboard.TargetProperty="Opacity" From="1" To="0" Duration="0:0:2" FillBehavior="HoldEnd" />
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Window.Triggers>

I get a error on , Value 'Window.Closing' cannot be assigned to property 'RoutedEvent'. Invalid event name.

回答1:

Closing is not a routed event, so you can't use it in an EventTrigger. Perhaps you could start the storyboard in the handler of the ClosingEvent in the code-behind and cancel the event... something like that :

private bool closeStoryBoardCompleted = false;

private void Window_Closing(object sender, CancelEventArgs e)
{
    if (!closeStoryBoardCompleted)
    {
        closeStoryBoard.Begin();
        e.Cancel = true;
    }
}

private void closeStoryBoard_Completed(object sender, EventArgs e)
{
    closeStoryBoardCompleted = true;
    this.Close();
}

回答2:

I thought I'd add another solution of doing this, using behaviors from the Expression SDK and combining it with the solution from @Thomas. Using that, we can define a "CloseBehavior" that handles the code behind of starting a storyboard and closing the window when it's done.

using System.ComponentModel;
using System.Windows;
using System.Windows.Interactivity;
using System.Windows.Media.Animation;

namespace Presentation.Behaviours {
    public class CloseBehavior : Behavior<Window> {
        public static readonly DependencyProperty StoryboardProperty =
            DependencyProperty.Register("Storyboard", typeof(Storyboard), typeof(CloseBehavior), new PropertyMetadata(default(Storyboard)));

        public Storyboard Storyboard {
            get { return (Storyboard)GetValue(StoryboardProperty); }
            set { SetValue(StoryboardProperty, value); }
        }

        protected override void OnAttached() {
            base.OnAttached();
            AssociatedObject.Closing += onWindowClosing;
        }

        private void onWindowClosing(object sender, CancelEventArgs e) {
            if (Storyboard == null) {
                return;
            }
            e.Cancel = true;
            AssociatedObject.Closing -= onWindowClosing;

            Storyboard.Completed += (o, a) => AssociatedObject.Close();
            Storyboard.Begin(AssociatedObject);
        }
    }
}

The behavior defines a storyboard as a dependency property, so we can set it in xaml and when the AssociatedObject (the window where we define the behavior) is closing, this storyboard is started using Storyboard.Begin(). Now, in xaml we simply add the behavior to the window using the following xaml

<Window x:Class="Presentation.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:behave="clr-namespace:Presentation.Behaviours"
        xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
        x:Name="window">
    <Window.Resources>
        <Storyboard x:Key="ExitAnimation">
            <DoubleAnimation Storyboard.Target="{Binding ElementName='window'}"
                             Storyboard.TargetProperty="(Window.Opacity)"
                             Duration="0:0:1" From="1" To="0"/>
        </Storyboard>
    </Window.Resources>

    <i:Interaction.Behaviors>
        <behave:CloseBehavior Storyboard="{StaticResource ExitAnimation}"/>
    </i:Interaction.Behaviors>

    <Grid>
    </Grid>
</Window>

Note the xml namespace i from the System.Windows.Interactivity dll, and also that the window is referenced, so it has to have a x:Name assigned. Now we simply add the behavior to every window on which we wish to execute a storyboard before closing the application, instead of copying the logic to every code-behind in each window.

回答3:

I'm not an expert on WPF but I believe that unless you cancel the initial Closing event the window will be gone before the animation is even started.

Upon receiving the Window.Closing event, you should cancel the event and start the animation. When the animation is done you can close the window.

回答4:

This is even simpler and shorter. Add a behavior as follows:

public class WindowClosingBehavior : Behavior<Window>
    {
        protected override void OnAttached()
        {
            AssociatedObject.Closing += AssociatedObject_Closing;
        }

        private void AssociatedObject_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            Window window = sender as Window;
            window.Closing -= AssociatedObject_Closing;
            e.Cancel = true;
            var anim = new DoubleAnimation(0, (Duration)TimeSpan.FromSeconds(0.5));
            anim.Completed += (s, _) => window.Close();
            window.BeginAnimation(UIElement.OpacityProperty, anim);
        }
        protected override void OnDetaching()
        {
            AssociatedObject.Closing -= AssociatedObject_Closing;
        }
    }

Then in your window add a reference :

xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:wt="clr-namespace:Desktop.Themes.WindowTask;assembly=Desktop.Themes"

Insert the behavior:

<i:Interaction.Behaviors>
     <wt:WindowClosingBehavior />
</i:Interaction.Behaviors>

回答5:

Set AutoReverse To "True"

<Window.Triggers>
        <EventTrigger RoutedEvent="Window.Loaded">
            <BeginStoryboard>
                <Storyboard>
                    <DoubleAnimation Storyboard.TargetProperty="Opacity" AutoReverse="True" From="0" To="1" Duration="0:0:0.5" FillBehavior="HoldEnd" />
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Window.Triggers>