Set Image Opacity with an DoubleAnimation

问题

This should be fairly simple but I can’t seem to get it right. I have a collection of System.Windows.Controls.Image. When I select one of them, I would like all the others to get an opacity of 0.5. I’m using MVVM, and the logic behind this (finding the selected image and setting it as Enabled) is done in the ViewModel, and is working. So basically this is working:

<Image Grid.Row="0" Source="{Binding ItemImage}" IsEnabled="{Binding ItemImageEnabled}">
<Image.Style>
    <Style TargetType="Image">
        <Style.Triggers>
            <Trigger Property="IsEnabled"  Value="False">
                <Setter Property="Opacity" Value="0.5"/>
            </Trigger>
            <Trigger Property="IsEnabled" Value="True">
                <Setter Property="Opacity" Value="1.0"/>
            </Trigger>
        </Style.Triggers>
    </Style>
</Image.Style>
</Image>

Now I would like the opacity shifting to be animated, fading it from 1.0 to 0.5 when the image is not selected, and fading from 0.5 to 1.0 when it is. I would have thought at this would work:

<Image Grid.Row="0" Source="{Binding ItemImage}" IsEnabled="{Binding ItemImageEnabled}">
<Image.Style>
    <Style TargetType="Image">
        <Style.Triggers>
            <Trigger Property="IsEnabled"  Value="False">
                <Trigger.EnterActions>
                    <BeginStoryboard>
                        <Storyboard>
                            <DoubleAnimation Storyboard.TargetProperty="Opacity" From="1" To="0.5" BeginTime="0:0:0" Duration="0:0:1"/>
                        </Storyboard>
                    </BeginStoryboard>
                </Trigger.EnterActions>
            </Trigger>
            <Trigger Property="IsEnabled" Value="True">
                <Trigger.EnterActions>
                    <BeginStoryboard>
                        <Storyboard>
                            <DoubleAnimation Storyboard.TargetProperty="Opacity" From="0.5" To="1" BeginTime="0:0:0" Duration="0:0:1"/>
                        </Storyboard>
                    </BeginStoryboard>
                </Trigger.EnterActions>
            </Trigger>
        </Style.Triggers>
    </Style>
</Image.Style>

... But it doesn't

Anybody have any idea. Any help would be greatly appreciated. Thanks in advance.

回答1:

You need Trigger.ExitActions instead of two Trigger. This should be what you want:

<Style TargetType="Image">
    <Style.Triggers>        
        <Trigger Property="IsEnabled" Value="True">
            <Trigger.EnterActions>
                <BeginStoryboard>
                    <Storyboard>
                        <DoubleAnimation Storyboard.TargetProperty="Opacity" From="0.5" To="1" BeginTime="0:0:0" Duration="0:0:1"/>
                    </Storyboard>
                </BeginStoryboard>
            </Trigger.EnterActions>
            <Trigger.ExitActions>
                <BeginStoryboard>
                    <Storyboard>
                        <DoubleAnimation Storyboard.TargetProperty="Opacity" From="1" To="0.5" BeginTime="0:0:0" Duration="0:0:1"/>
                    </Storyboard>
                </BeginStoryboard>
            </Trigger.ExitActions>
        </Trigger>
    </Style.Triggers>
</Style>

来源：https://stackoverflow.com/questions/35942800/set-image-opacity-with-an-doubleanimation

标签

wpf

xaml

mvvm

doubleanimation