what's wrong with my wpf animation code

Question

I'd like to repeat my animation for several times, every time the property of a target would change with it triggered or animation completed.

But the animition works only for the first time.

To simplify this, I just let a rectangle move from 0 to 400 in a canvas for 10 times. The code is followed.

I have searched questions like 'wpf repeat animation', which suggested to use seek() method or rect.BeginAnimation(property, null), but doesn't work for me.

private void init()
{
    Rectangle rect = new Rectangle();
    this.RegisterName("rect", rect);
    rect.Height = 100;
    rect.Width = 50;
    rect.Fill = Brushes.LightBlue;
    Canvas.SetTop(rect, 0);
    Canvas.SetLeft(rect, 0);
    myCanvas.Children.Add(rect);

    TargetAnimation(0);
}

private void TargetAnimation(int i)
{
    DoubleAnimation da = new DoubleAnimation();
    da.From = 0;
    da.To = 400;
    da.Duration = TimeSpan.FromSeconds(5);

    Storyboard.SetTargetName(da, "rect");
    Storyboard.SetTargetProperty(da, new PropertyPath(Canvas.LeftProperty));
    Storyboard storyboard = new Storyboard();
    storyboard.Children.Add(da);
    storyboard.Completed += Storyboard_Completed;
    storyboard.Begin(this);

}

private void Storyboard_Completed(object sender, EventArgs e)
{
    if (i < 10)
        TargetAnimation(++i);
    else
        return;
}

Why are you passing an argument `i` to your `TargetAnimation` method? you are not using it... — Pikoh, May 23 '16 at 08:48
Why not use the `da.RepeatBehavior = RepeatBehavior.Forever;`? — Jeroen van Langen, May 23 '16 at 08:56
I'm sorry for not making it clear. `i` is a global argument. @Pikoh — HDQ, May 23 '16 at 09:51
I just simplified the problem. Actually I need to change properties of the target every time like moving distance or duration. @JeroenvanLangen — HDQ, May 23 '16 at 09:54

score 3 · Accepted Answer · answered May 23 '16 at 09:08

3

you should register completed event first before calling begin statement like this:

storyboard.Completed += Storyboard_Completed;
 storyboard.Begin(this);

answered May 23 '16 at 09:08

tabby

1,878
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score 2 · Answer 2 · answered May 23 '16 at 09:06

I think you misunderstand StoryBoard.Completed. You should apply the delegate on da.Completed.

        private void TargetAnimation(int i)
        {
            DoubleAnimation da = new DoubleAnimation();
            da.From = 0;
            da.To = 400;
            da.Duration = TimeSpan.FromSeconds(5);
            da.Completed += Storyboard_Completed;
            Storyboard.SetTargetName(da, "rect");
            Storyboard.SetTargetProperty(da, new PropertyPath(Canvas.LeftProperty));
            Storyboard storyboard = new Storyboard();
            storyboard.Children.Add(da);
            storyboard.Begin(this);
            //storyboard.Completed += Storyboard_Completed;
        }

score 0 · Answer 3 · answered May 23 '16 at 09:02

0

You passed i as a parameter but you did not use it or its value to determine. So you have to limit TargetAnimation(int i) value using if statement that is equal to the target animation value which is i

answered May 23 '16 at 09:02

Kindle Q

944
2
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what's wrong with my wpf animation code

3 Answers3