4

Currently I have the following code to flash a DataGrid cell when it's value changes:

<TextBlock Background="White" Text={Binding Date, NotifyOnTargetUpdated=True} >
    <EventTrigger RoutedEvent="Binding.TargetUpdated" >
        <BeginStoryboard>
            <Storyboard>
                <ColorAnimation AutoReverse="True" From="#1F1F1F" To="#FFFF88" Duration="0:0:0.2" Storyboard.TargetProperty="Background.Color" FillBehavior="Stop" />
            </Storyboard>
        </BeginStoryboard>
    </EventTrigger>
</TextBlock>

Now I need to execute this animation only if a boolean value of the viewmodel is true. How can I accomplish this?

EDIT: Extended the sample

Thanks.

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10
  • Any chance of a working sample? Commented Jun 7, 2012 at 16:41
  • Why DataTrigger isn't an option ? It's precisely what you ask for... Commented Jun 7, 2012 at 17:00
  • @dodsky do you mean why I use an EventTrigger instead of a DataTrigger? Commented Jun 7, 2012 at 17:11
  • @SoMoS Yes, I'm wondering. DataTrigger will trigger an action when your boolean value changes... Commented Jun 7, 2012 at 17:16
  • @dodsky it's not a boolean value, it's a DateTime value, the boolean is the one that controls if the animation has to be shown or not, the binded value it's a DateTime. Commented Jun 7, 2012 at 17:20

3 Answers 3

Reset to default
2

Thanks to XAML guy for his answer on another forum. This is the answer to the question, the solution is to use the following attached behaviour:

class AttachedBehaviours
{
    public static bool GetAllowTargetUpdated(DependencyObject obj)
    {
        return (bool)obj.GetValue(AllowTargetUpdatedProperty);
    }

    public static void SetAllowTargetUpdated(DependencyObject obj, bool value)
    {
        obj.SetValue(AllowTargetUpdatedProperty, value);
    }

    // Using a DependencyProperty as the backing store for AllowTargetUpdated.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty AllowTargetUpdatedProperty =
        DependencyProperty.RegisterAttached("AllowTargetUpdated", typeof(bool), typeof(AttachedBehaviours), new UIPropertyMetadata(false, PropChanged));


    static void PropChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        var ele = obj as FrameworkElement;
        var be = ele.GetBindingExpression(TextBlock.TextProperty);
        if (be == null) return;

        var b = be.ParentBinding;

        var newBinding = new Binding(b.Path.Path);
        newBinding.NotifyOnTargetUpdated = (bool)e.NewValue;

        ele.SetBinding(TextBlock.TextProperty, newBinding);
    }
}

And this is its usage from XAML:

<TextBlock Background="White" Text="{Binding Date}"  local:AttachedBehaviours.AllowTargetUpdated="{Binding EnableAnimations}" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,10,0,0"  >
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Comments

1

Have you tried something like this:

<ControlTemplate.Triggers>
    <DataTrigger Value="false">
        <DataTrigger.EnterActions>
            <BeginStoryboard> 
            <Storyboard> 
                <ColorAnimation AutoReverse="True" From="#1F1F1F" To="#FFFF88" Duration="0:0:0.2" Storyboard.TargetProperty="Background.Color" FillBehavior="Stop" /> 
            </Storyboard> 
        </BeginStoryboard> 

       </DataTrigger.EnterActions>
    </DataTrigger>
</ControlTemplate.Triggers>
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3 Comments

I need to fire the animation on value change, the value is not a boolean so I cannot compare the value with anything, that's why I use a EventTrigger.
@SoMoS Fire it for a specific value or just the value changing?
Just for the value changing to inform to the end user that the value changed with a flash
1

Well, this is how I solved the problem. Probably is one of the ugliest codes I ever wrote so feel free to propose something better.

I've created a converter that I bind to the duration using the boolean value that enables / disables the animation. Something like this:

class AnimationEnablerConverter : IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        bool enableAnimation = (bool)value;

        if (enableAnimation)
        {
            return new System.Windows.Duration(new TimeSpan(0, 0, 0, 0, 200));
        }
        else
        {
            return new System.Windows.Duration(new TimeSpan(0, 0, 0, 0, 0));
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    #endregion
}

And the xaml:

<ColorAnimation AutoReverse="True" From="#1F1F1F" To="#FFFF88" Duration="{Binding IsAnimationEnabled, Converter={StaticResource anim2}}" Storyboard.TargetProperty="Background.Color" FillBehavior="Stop" />
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1 Comment

Ou shit! This is not working either because freezable elements cannot be binded. I'm getting a 'Cannot freeze this Storyboard timeline tree for use across threads' error. WTF!!!

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