Question

如何在WPF中将元素的宽度从0设置为实际宽度？

我试过了：

<ControlTemplate.Triggers>
    <EventTrigger RoutedEvent="Loaded">
        <BeginStoryboard>
            <Storyboard>
                <DoubleAnimation Duration="0:0:0.3" To="{Binding ElementName=MyElement, Path=ActualWidth}" From="0" Storyboard.TargetProperty="Width" Storyboard.TargetName="MyElement" />
            </Storyboard>
        </BeginStoryboard>
    </EventTrigger>
</ControlTemplate.Triggers>

如果我将绑定更改为硬编码值（如100），则宽度会正确设置动画，但我想绑定到元素的实际宽度。

如果重要，MyElement是边框，我正在为标签项设置动画。

对于记录，这也不起作用：

To="{Binding RelativeSource={RelativeSource AncestorType={x:Type Border}}, Path=ActualWidth}"

Answer 1

由于很多原因，我确定这是错误的，请随时告诉我我违反了多少WPF法则但是......我通过创建自己的BindableDoubleAnimation解决了同样的问题。

public class BindableDoubleAnimation : DoubleAnimationBase
{
    DoubleAnimation internalAnimation;

    public DoubleAnimation InternalAnimation { get { return internalAnimation; } }

    public double To
    {
        get { return (double)GetValue(ToProperty); }
        set { SetValue(ToProperty, value); }
    }

    /// <summary>
    /// Dependency backing property for the <see cref="To"/> property.
    /// </summary>
    public static readonly DependencyProperty ToProperty =
        DependencyProperty.Register("To", typeof(double), typeof(BindableDoubleAnimation), new UIPropertyMetadata(0d, new PropertyChangedCallback((s, e) =>
            {
                BindableDoubleAnimation sender = (BindableDoubleAnimation)s;
                sender.internalAnimation.To = (double)e.NewValue;
            })));


    public double From
    {
        get { return (double)GetValue(FromProperty); }
        set { SetValue(FromProperty, value); }
    }

    /// <summary>
    /// Dependency backing property for the <see cref="From"/> property.
    /// </summary>
    public static readonly DependencyProperty FromProperty =
        DependencyProperty.Register("From", typeof(double), typeof(BindableDoubleAnimation), new UIPropertyMetadata(0d, new PropertyChangedCallback((s, e) =>
        {
            BindableDoubleAnimation sender = (BindableDoubleAnimation)s;
            sender.internalAnimation.From = (double)e.NewValue;
        })));


    public BindableDoubleAnimation()
    {
        internalAnimation = new DoubleAnimation();
    }

    protected override double GetCurrentValueCore(double defaultOriginValue, double defaultDestinationValue, AnimationClock animationClock)
    {
        return internalAnimation.GetCurrentValue(defaultOriginValue, defaultDestinationValue, animationClock);
    }

    protected override Freezable CreateInstanceCore()
    {
        return internalAnimation.Clone();;
    }
}

我现在可以自由地为To From属性使用绑定。

<local:BindableDoubleAnimation Storyboard.TargetProperty="Width" From="0" To="{Binding ActualWidth, RelativeSource={RelativeSource AncestorType=Window}}"/>

Answer 2

动画中不能使用绑定是一个常见问题。

一种解决方法是使用具有SourceValue＆amp;的辅助对象。 TargetValue（你可以绑定到你想要的任何内容，包括ActualWidth）a CurrentValue（返回动画值）和Progress，可以从0.0到100.0进行动画处理。当进度发生变化时，您只需计算CurrentValue，然后可以绑定对象的Width。它不漂亮但应该有用。

WPF中的动画宽度到实际宽度？

2 个答案: