UWP Simple Animation using MVVM

Indudhar Gowda 426 Reputation points
2020-06-25T12:50:51.427+00:00

UWP Simple Animation using MVVM..

Just need the below code to animate using MVVM...*Not code behind

10629-1.png

microsoft-ui-xaml

Important ...It should work in below Target Version.
10685-10158-2.png

Universal Windows Platform (UWP)
{count} votes

Accepted answer
  1. Daniele 1,996 Reputation points
    2020-06-25T17:14:50.54+00:00

    The problem is that UIElement.StartAnimation is available from 10.0.17763.0 and your min version is 10.0.17134.0. You can use animation through visual layer anyway.
    As I do not like to have such kind of code in view model, I propose to you a different solution using Microsoft.Xaml.Interactivity.

    Solution with behaviors

    Extend Microsoft.Xaml.Interactivity.Behavior

    public class ScaleBehavior : Behavior
    {
        private readonly Compositor _compositor = Window.Current.Compositor;
        private SpringVector3NaturalMotionAnimation _springAnimation;
        private Visual _elementVisual;
    
        protected override void OnAttached()
        {
            if (!(AssociatedObject is UIElement uiElement)) return;
    
            uiElement.PointerEntered += Element_PointerEntered;
            uiElement.PointerExited += Element_PointerExited;
            _elementVisual = ElementCompositionPreview.GetElementVisual(uiElement);
        }
    
        protected override void OnDetaching()
        {
            if (!(AssociatedObject is UIElement uiElement)) return;
    
            uiElement.PointerEntered -= Element_PointerEntered;
            uiElement.PointerExited -= Element_PointerExited;
            _elementVisual = null;
        }
    
        private void Element_PointerEntered(object sender, PointerRoutedEventArgs e)
        {
            CreateOrUpdateSpringAnimation(1.5f);
            Vector2 size = _elementVisual.Size;
            _elementVisual.CenterPoint = new Vector3(size.X / 2, size.Y / 2, 0);
            _elementVisual.StartAnimation("Scale", _springAnimation);
        }
    
        private void Element_PointerExited(object sender, PointerRoutedEventArgs e)
        {
            CreateOrUpdateSpringAnimation(1.0f);
            Vector2 size = _elementVisual.Size;
            _elementVisual.CenterPoint = new Vector3(size.X / 2, size.Y / 2, 0);
            _elementVisual.StartAnimation("Scale", _springAnimation);
        }
    
        private void CreateOrUpdateSpringAnimation(float finalValue)
        {
            if (_springAnimation == null) _springAnimation = _compositor.CreateSpringVector3Animation();
            _springAnimation.FinalValue = new Vector3(finalValue);
        }
    }
    

    and add to your XAML

    <Border BorderBrush="Red" BorderThickness="2" HorizontalAlignment="Center" VerticalAlignment="Center">
        <interactivity:Interaction.Behaviors>
            <appShell:ScaleBehavior/>
        </interactivity:Interaction.Behaviors>
        <TextBox Text="HELP"/>
    </Border>
    

    Solution with code in view model

    <Page x:Class="UwpApp.AppShell.MainPage"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
          xmlns:local="using:UwpApp.AppShell"
          mc:Ignorable="d"
          Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Page.DataContext>
            <local:ViewModel x:Name="ViewModel"/>
        </Page.DataContext>
        <Grid>
            <Border BorderBrush="Red" BorderThickness="2" HorizontalAlignment="Center" VerticalAlignment="Center"
                    PointerEntered="{x:Bind ViewModel.PointerEntered}" PointerExited="{x:Bind ViewModel.PointerExited}">
                <TextBox Text="HELP"/>
            </Border>
        </Grid>
    </Page>
    
    
    
    public class ViewModel
    {
        private readonly Compositor _compositor = Window.Current.Compositor;
        private SpringVector3NaturalMotionAnimation _springAnimation;
    
        public void PointerEntered(object sender, PointerRoutedEventArgs e)
        {
            CreateOrUpdateSpringAnimation(1.5f);
            Visual elementVisual = ElementCompositionPreview.GetElementVisual((UIElement) sender);
            Vector2 size = elementVisual.Size;
            elementVisual.CenterPoint = new Vector3(size.X / 2, size.Y / 2, 0);
            elementVisual.StartAnimation("Scale", _springAnimation);
        }
    
        public void PointerExited(object sender, PointerRoutedEventArgs e)
        {
            CreateOrUpdateSpringAnimation(1.0f);
            Visual elementVisual = ElementCompositionPreview.GetElementVisual((UIElement)sender);
            Vector2 size = elementVisual.Size;
            elementVisual.CenterPoint = new Vector3(size.X / 2, size.Y / 2, 0);
            elementVisual.StartAnimation("Scale", _springAnimation);
        }
    
        private void CreateOrUpdateSpringAnimation(float finalValue)
        {
            if (_springAnimation == null) _springAnimation = _compositor.CreateSpringVector3Animation();
            _springAnimation.FinalValue = new Vector3(finalValue);
        }
    }
    
    2 people found this answer helpful.

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