WPF元素在可视化树中，但不是动画？

Question

I'm trying to figure out how to generate animations procedurally. I create a Line, create four animations, and associate the line's endpoints to the animations. I add the animations to a storyboard, then I run the storyboard.

The panel itself is visible (I could change the background orange, and that change shows up), but not its children. The heck am I doing wrong?

Code behind:

using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;
using System.Windows.Media.Animation;

namespace MyProject.Animations
{
    public class MyAnimation : Panel
    {
        private DoubleAnimation[] lineAnimation;
        private Line line;
        private Storyboard storyboard;

        public MyAnimation()
        {
            storyboard = new Storyboard();

            line = new Line();
            line.StrokeThickness = 4;
            line.Stroke = Brushes.Black;
            this.Children.Add(line);    

            lineAnimation = new DoubleAnimation[4];
            for (int i = 0; i < 4; i++)
            {
                lineAnimation[i] = new DoubleAnimation();
                lineAnimation[i].Duration = new Duration(TimeSpan.FromSeconds(5));
                lineAnimation[i].AutoReverse = true;
                lineAnimation[i].RepeatBehavior = RepeatBehavior.Forever;

                lineAnimation[i].From = 10 * i;
                lineAnimation[i].To = 100 * i;

                storyboard.Children.Add(lineAnimation[i]);
            }

            Storyboard.SetTarget(lineAnimation[0], line);
            Storyboard.SetTargetProperty(lineAnimation[0], new PropertyPath("X1"));

            Storyboard.SetTarget(lineAnimation[1], line);
            Storyboard.SetTargetProperty(lineAnimation[1], new PropertyPath("Y1"));

            Storyboard.SetTarget(lineAnimation[2], line);
            Storyboard.SetTargetProperty(lineAnimation[2], new PropertyPath("X2"));

            Storyboard.SetTarget(lineAnimation[3], line);
            Storyboard.SetTargetProperty(lineAnimation[3], new PropertyPath("Y2"));

            storyboard.Begin();
        }
    }
}

XAML:

<Window x:Class="MyProject.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:sdk="http://schemas.microsoft.com/netfx/2009/xaml/presentation/sdk"
        xmlns:local="clr-namespace:MyProject"
        xmlns:a="clr-namespace:Myproject.Animations"
        Title="MyProject">

    <Grid>
        <a:MyAnimation>
    </Grid>

</Window>

Inspecting the application with Snoop, I see my lines in the visual tree. But they're not being drawn. (Note, this is the debug window for the actual application, not the representative code sample I've transcribed.)

Answer 1

When you derive from Panel , the Children are not laid out. You would also have to override the MeasureOverride and ArrangeOverride methods. See How to: Create a Custom Panel Element for details.

Or simply derive from Canvas instead:

public class MyAnimation : Canvas
{
    ...
}