WPF可视化器
可视树
画布
canvas.Children.Add poly |> ignore
指定的可视对象是:
- 已经是另一个可视对象的子元素,或者
- 是CompositionTarget的根元素。
看起来不像是1),不确定2)是什么?
使用Visual Studio 2010、F# 2.0、WPF...而非XAML
没有相关的代码示例,所以诊断问题有些困难,但也许问题在于您试图将相同的多边形添加到画布的子项中两次。
这是我为了重现您的错误而编写的代码:
type SimpleWindow() as this =
inherit Window()
do
let makepoly size corners =
let size = 192.0
let angle = 2.0 * Math.PI / float corners
let getcoords size angle = new Point(size * cos angle, size * sin angle)
let poly = new Polygon(Fill = Brushes.Red)
poly.Points <- new PointCollection([for i in 0..corners-1 -> getcoords size (float i * angle)])
poly
let canvas = new Canvas(HorizontalAlignment = HorizontalAlignment.Center,
VerticalAlignment = VerticalAlignment.Center)
let poly = makepoly 192.0 5
Canvas.SetLeft(poly, canvas.Width / 2.0)
Canvas.SetTop(poly, canvas.Width / 2.0)
canvas.Children.Add poly |> ignore //this works
this.AddChild canvas |> ignore
SimpleWindow().Show()
如果我添加另一个canvas.Children.Add poly
,它会崩溃并显示您的错误信息。canvas.Children.Add poly |> ignore
canvas.Children.Add poly |> ignore //this fails, poly already exists on the canvas
为了修复这个错误,我首先调用了canvas.Children.Remove
来删除特定的子元素,以便将其替换为另一个。canvas.Children.Add poly |> ignore
canvas.Children.Remove poly
canvas.Children.Add poly |> ignore //this works, because the previous version is gone
我希望这可以解决你的问题。