Theme Transition

Theme Transition shows how you can create Transitions that apply to elements within an application using the Windows App SDK.

Step 1

Follow Setup and Start on how to get Setup and Install what you need for Visual Studio 2022 and Windows App SDK.

Step 2

Then in Visual Studio within Solution Explorer for the Solution, right click on the Project shown below the Solution and then select Add then New Item…

Step 3

Then in Add New Item from the C# Items list, select Code and then select Code File from the list next to this, then type in the name of Library.cs and then Click on Add.

Step 4

You will now be in the View for the Code of Library.cs, within this type the following Code:

using Microsoft.UI;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Media;
using Microsoft.UI.Xaml.Shapes;
using System.Collections.Generic;
using System.Linq;
using Windows.UI;

internal class Library
{
    private static readonly List<Color> _colours = new()
    {
        Colors.Black, Colors.Gray, Colors.Red, Colors.Orange, Colors.Yellow,
        Colors.Green, Colors.Cyan, Colors.Blue, Colors.Magenta, Colors.Purple
    };

    private static int _index = 0;

    public static void Add(StackPanel panel)
    {
        Rectangle previous = panel.Children.LastOrDefault() as Rectangle;
        if(previous == null || _index == _colours.Count)
        {
            _index = 0;
        }
        panel.Children.Add(new Rectangle()
        {
            Width = 50,
            Height = 50,
            Fill = new SolidColorBrush(_colours[_index])
        });
        _index++;
    }

    public static void Remove(StackPanel panel)
    {
        int count = panel.Children.Count;
        if (count > 0)
        {
            panel.Children.RemoveAt(count - 1);
        }
    }
}                                                                                                                                                                                                                                                                                                                  
                                    

The Class that has been defined in Library.cs has List of Color for the colours to use for elements along with an int value for keeping track of which one will be used. Then there is a Method of Add, which will add a Rectangle to a StackPanel with the given next colour to use and the Method of Remove, which will remove added Rectangle elements from a StackPanel.

Step 5

Step 6

In the XAML for MainWindow.xaml there will be some XAML for a StackPanel, this should be Removed:

<StackPanel Orientation="Horizontal" 
HorizontalAlignment="Center" VerticalAlignment="Center">
    <Button x:Name="myButton" Click="myButton_Click">Click Me</Button>
</StackPanel>                               
                                    

Step 7

While still in the XAML for MainWindow.xaml above </Window>, type in the following XAML:

<Grid>
    <Viewbox Margin="25">
        <StackPanel Name="Display" Spacing="5" 
            Orientation="Horizontal" HorizontalAlignment="Center">
            <StackPanel.ChildrenTransitions>
                <TransitionCollection>
                    <EntranceThemeTransition IsStaggeringEnabled="True" />
                </TransitionCollection>
            </StackPanel.ChildrenTransitions>
        </StackPanel>
    </Viewbox>
    <CommandBar VerticalAlignment="Bottom" HorizontalAlignment="Stretch" >
        <AppBarButton Icon="Add" Label="Add" Click="Add_Click"/>
        <AppBarButton Icon="Remove" Label="Remove" Click="Remove_Click"/>
    </CommandBar>
</Grid>                                                                                                                                                                                                                                      
                                    

This XAML features a Grid with a ViewBox to Scale elements and in this is a StackPanel which has the Theme Transition set for the ChildrenTransitions of EntranceThemeTransition with an AppBarButton to Add and Remove elements.

Step 8

Step 9

In the Code for MainWindow.xaml.cs there be a Method of myButton_Click(...) this should be Removed by removing the following:

private void myButton_Click(object sender, RoutedEventArgs e)
{
    myButton.Content = "Clicked";
}                                        
                                    

Step 10

Once myButton_Click(...) has been removed, type the following Code below the end of the Constructor of public MainWindow() { ... }:

private void Add_Click(object sender, RoutedEventArgs e)
{
    Library.Add(Display);
}

private void Remove_Click(object sender, RoutedEventArgs e)
{
    Library.Remove(Display);
}                                                                                                                                                                                                                                                                                                                                                                                                                          
                                    

The Methods of Add_Click and Remove_Click will when Clicked will call the Methods within Library.cs of Add and Remove from Library passing in the StackPanel.

Step 11

Step 12

Once running you should see the AppBarButton for Add and Remove.

Step 13

You can select the AppBarButton for Add to add some elements and they should appear with a Theme Transition.

Step 14