在SizeChanged事件上调整动画大小无法正常工作

Question

我希望在将StackPanel的可见性设置为可见状态时调整动画大小，但与此相反，我变得无休止地闪烁了包含StackPanel的边框。我认为我做错了。 堆栈面板包含TextBlock的实例。

private void MyBorder_SizeChanged_1(object sender, SizeChangedEventArgs e)
{
    if (!first)
    {
        DoubleAnimation anim = new DoubleAnimation();
        anim.From = e.PreviousSize.Height;
        anim.To = e.NewSize.Height;
        anim.Duration = new Duration(TimeSpan.FromSeconds(1));
        Storyboard.SetTarget(anim, MyBorder);
        Storyboard.SetTargetProperty(anim, new PropertyPath(Border.HeightProperty));
        Storyboard st = new Storyboard();
        st.Children.Add(anim);
        st.Begin();
    }
    first = false;
}

private void MyBorder_Tap_1(object sender, GestureEventArgs e)
{
    if (MyPanel.Visibility == Visibility.Collapsed)
        MyPanel.Visibility = Visibility.Visible;
    else
        MyPanel.Visibility = Visibility.Collapsed;
}

Answer 1

问题在于，当对边框的高度进行动画处理时，它将触发SizeChanged事件，因此会产生一个循环：大小更改事件>动画高度>大小更改事件>。
同样，在触发了大小更改事件时，大小更改已被放置，因此即使该大小可行，当您返回动画时，您也会有一些轻弹。
最后，在动画中使用HEight会强制进行渲染更新，因此不会硬件加速。 最好的办法是执行“转换”变换或“缩放”变换。
例如，您可以在tap事件中直接在MyPanel上进行0到1之间的比例转换。

Answer 2

这可能会帮助您。 这是一个变通

private void MyBorder_SizeChanged_1(object sender, SizeChangedEventArgs e)
    {
        if (!first)
        {
            DoubleAnimation anim = new DoubleAnimation();
            anim.From = e.PreviousSize.Height;
            anim.To = e.NewSize.Height;
            anim.Duration = new Duration(TimeSpan.FromSeconds(1));
            Storyboard.SetTarget(anim, MyBorder);
            Storyboard.SetTargetProperty(anim, new PropertyPath(Border.HeightProperty));
            Storyboard st = new Storyboard();
            st.Children.Add(anim);
            st.Completed += st_Completed;
            MyBorder.SizeChanged -= MyBorder_SizeChanged_1;
            st.Begin();

        }
        first = false;
    }

    void st_Completed(object sender, EventArgs e)
    {
        MyBorder.SizeChanged += MyBorder_SizeChanged_1;
    }

    private void MyBorder_Tap_1(object sender, GestureEventArgs e)
    {
        if (MyPanel.Visibility == Visibility.Collapsed)
            MyPanel.Visibility = Visibility.Visible;
        else
            MyPanel.Visibility = Visibility.Collapsed;


    }

考虑到即使在情节提要中，边框的大小都已调整，因此最好删除大小更改的事件。 尝试对chld大小的父容器进行动画处理，从而改变了这种情况

Answer 3

我已经解决了这个问题。 愚蠢的我，我认为StackPanel的Measure方法是私有的，并且不必费心去确保它，这是在Click上扩展StackPanel的解决方案代码。

 private void MyBorder_Tap_1(object sender, GestureEventArgs e) { if (MyPanel.Visibility == Visibility.Collapsed) { MyPanel.Visibility = Visibility.Visible; MyPanel.Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity)); DoubleAnimation anim = new DoubleAnimation(); anim.From = MyBorder.ActualHeight; anim.To = MyBorder.ActualHeight + MyPanel.DesiredSize.Height; anim.Duration = new Duration(TimeSpan.FromSeconds(0.25)); Storyboard.SetTarget(anim, MyBorder); Storyboard.SetTargetProperty(anim, new PropertyPath(Border.HeightProperty)); Storyboard st = new Storyboard(); st.Children.Add(anim); st.Begin(); } else { MyPanel.Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity)); DoubleAnimation anim = new DoubleAnimation(); anim.From = MyBorder.ActualHeight; anim.To = MyBorder.ActualHeight - MyPanel.DesiredSize.Height; anim.Duration = new Duration(TimeSpan.FromSeconds(0.25)); Storyboard.SetTarget(anim, MyBorder); Storyboard.SetTargetProperty(anim, new PropertyPath(Border.HeightProperty)); Storyboard st = new Storyboard(); st.Children.Add(anim); st.Completed += (a,b) => { MyPanel.Visibility = Visibility.Collapsed; }; st.Begin(); } }