WPF 中的动画渲染转换

Question

我有一个关于 C# 代码中 WPF 动画的问题！
我有一个 MouseWheel 事件的处理函数。它只是检查您是“放大”还是“缩小”。看一下代码，这里重要的一行是第 4 行，这里设置了 RenderTransform。

    private void ZoomPanCanvas_MouseWheel(object sender, MouseWheelEventArgs e) {
        var factor = (e.Delta > 0) ? (1.1) : (1 / 1.1);
        currrentScale = factor * currrentScale;
        mNetworkUI.RenderTransform = new ScaleTransform(currrentScale, currrentScale);
        var pos = e.GetPosition(mNetworkUI);
        mNetworkUI.Width = ZoomPanCanvas.ActualWidth / currrentScale;
        mNetworkUI.Height = ZoomPanCanvas.ActualHeight /currrentScale;
        var dummyTransform = new ScaleTransform(factor, factor, pos.X, pos.Y);
        var offSet = new Point(dummyTransform.Value.OffsetX, dummyTransform.Value.OffsetY);
        mNetworkUI.ViewModel.Network.SetTransformOffset(offSet);
    }

为了完整起见，我将函数的其余部分保留在代码中。
我想要做的是对 RenderTransform 的这种变化进行动画处理！

我已经尝试使用 Storyboard（设置了 UIElement.RenderTransformProperty）。最好的结果是对 RenderTransform 进行非动画更改（但它与代码中的第 4 行实现的结果不同）。

也许你可以帮助我，我已经尝试了这里其他问题的一些建议方法。

编辑：

这是无效的尝试，首先是上面的 chenged 代码：

    private void ZoomPanCanvas_MouseWheel(object sender, MouseWheelEventArgs e) {
        var factor = (e.Delta > 0) ? (1.1) : (1 / 1.1);
        currrentScale = factor * currrentScale;
        ///mNetworkUI.RenderTransform = new ScaleTransform(currrentScale, currrentScale);
        Helper.Animations.RenderTransformAnimation(mNetworkUI, new ScaleTransform(currrentScale, currrentScale));
        var pos = e.GetPosition(mNetworkUI);
        mNetworkUI.Width = ZoomPanCanvas.ActualWidth / currrentScale;
        mNetworkUI.Height = ZoomPanCanvas.ActualHeight /currrentScale;
        var dummyTransform = new ScaleTransform(factor, factor, pos.X, pos.Y);
        var offSet = new Point(dummyTransform.Value.OffsetX, dummyTransform.Value.OffsetY);
        mNetworkUI.ViewModel.Network.SetTransformOffset(offSet);
    }

它遵循静态辅助函数：

    public static void RenderTransformAnimation(FrameworkElement element, Transform newTransform) {
        MatrixAnimationUsingKeyFrames anim = new MatrixAnimationUsingKeyFrames();
        var key1 = new DiscreteMatrixKeyFrame(element.RenderTransform.Value, KeyTime.FromPercent(0));
        var key2 = new DiscreteMatrixKeyFrame(newTransform.Value, KeyTime.FromPercent(1));

        Storyboard.SetTarget(anim, element.RenderTransform);
        Storyboard.SetTargetProperty(anim, new PropertyPath(UIElement.RenderTransformProperty));
        Storyboard sb = new Storyboard();
        sb.Children.Add(anim);
        sb.Duration = AnimationDuration;
        sb.Begin();
    }

它总是在 sb.Begin() 调用中引发异常，告诉我，我的“PropertyPath”有问题。我不知道该怎么做:(。 我的意思是，没有办法直接创建“TransformAnimation”，对吧？只有 MatrixAnimations 可用...

Answer 1

我在下面提供了ScaleTransform 的简单动画。为了提供一个“最小”的例子，我只调整了比例；我不会根据鼠标位置进行任何偏移计算。你应该能够弄清楚从这里去哪里：

private void OnMouseWheel(object sender, MouseWheelEventArgs e)
{
    var factor = e.Delta > 0d ? 1.1d : 0.9d;

    var t = mNetworkUI.RenderTransform as ScaleTransform;
    if (t == null)
    {
        mNetworkUI.RenderTransform = t = new ScaleTransform(1d, 1d)
                                         {
                                             CenterX = 0.5d,
                                             CenterY = 0.5d
                                         };
    }

    var oldScale = (double)t.GetAnimationBaseValue(ScaleTransform.ScaleXProperty);
    var newScale = oldScale * factor;

    //
    // Make sure `GetAnimationBaseValue()` reflects the `To` value next time
    // (needed to calculate `oldScale`, and for the animation to infer `From`).
    //
    t.ScaleX = newScale;
    t.ScaleY = newScale;

    var animation = new DoubleAnimation
                    {
                        To = newScale,
                        Duration = TimeSpan.FromSeconds(0.5d),
                        DecelerationRatio = 0.5d,
                        FillBehavior = FillBehavior.Stop
                    };

    //
    // Use `HandoffBehavior.Compose` to transition more smoothly if an animation
    // is already in progress.
    //
    t.BeginAnimation(
        ScaleTransform.ScaleXProperty, 
        animation, 
        HandoffBehavior.Compose);

    t.BeginAnimation(
        ScaleTransform.ScaleYProperty,
        animation,
        HandoffBehavior.Compose);
}