带BitmapCache的画布-删除子对象后渲染 [英] Canvas with BitmapCache - Render after removing child

问题描述

我有一个包含以下元素的用户控件:

I have a user control that contains the following elements:

<UserControl
 ...>
  <ScrollViewer Name="LayoutScroll" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto">

    <Grid Name="MainGrid">
      <Canvas x:Name="LayerObjects" Panel.ZIndex="2"
       Width="{Binding ActualWidth,ElementName=MainGrid}" Height="{Binding ActualHeight, ElementName=MainGrid}">
            <Canvas.CacheMode>
                <BitmapCache 
                EnableClearType="False" 
                SnapsToDevicePixels="False"
                RenderAtScale="2"/>
            </Canvas.CacheMode>
        </Canvas>
    </Grid>

  </ScrollViewer>
</UserControl>

我使用此用户控件将多个形状绘制到其中.绘图工作正常，删除工作也正常(我不知道我做了什么更改，只是无法弄清楚).每次我想从画布上删除一个元素时，我都会简单地做:

I use this user control to have multiple shapes drawn into it. The drawing is working perfectly and the removing was working as well (I dont know what have I changed, just cant figure it out). Every time I want to remove an element from this canvas I would just simply do:

LayerObject.Children.Remove(shape);

现在，当我执行此操作时，就不会从画布上从视觉上删除该形状.它只是呆在那里.当我移动窗口或放大画布时，形状消失了.因此，我的问题是，一旦元素被删除，是否有任何方法可以渲染"画布?

Now, when I do that the shape is not visually removed from the canvas. It just stays there. When I move the window or zoom into the canvas the shape dissapears. So, my question is, is there any way to "render" the canvas as soon as the element is removed ?

到目前为止，我尝试了什么(没有成功):

What have I tried so far (without success):

• oCanvas.UpdateLayout();
• oCanvas.InvalidateVisual();
• 验证删除操作是否正在调度程序上运行.
• 如果删除了CacheMode，但在处理多种形状时会失去性能.

推荐答案

我已解决此问题，方法是在更改Canvas子级之前先删除CacheMode，然后再将其重新启用.

I've resolved this by removing the CacheMode before changing the Canvas children and then put it back on.

CacheMode oTempCM = oCanvas.CacheMode;
oCanvas.CacheMode = null;
//do canvas operations ...
oCanvas.CacheMode = oTempCM;

谢谢@Clemens.

Thank you @Clemens.

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