moving circle in canvas

Question

i'm trying to move a green circle in side a canvas and when the circle become inside the red circle it will change it's color.

the problem is:

1-I can't find the position (x,y) of the green circle after move

2- how can I now if the green circle in side the red one?

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Canvas x:Name="maincanvas"  HorizontalAlignment="Left" Height="436" Margin="125,122,0,0" VerticalAlignment="Top" Width="1130" Background="#FFEAE2E2">
            <Ellipse x:Name="redcircle"  Fill="Red" Height="182" Canvas.Left="577" Stroke="Black" Canvas.Top="141" Width="188"/>
            <Ellipse x:Name="greencircle" Fill="Green" Height="100" Canvas.Left="225" Stroke="Black" Canvas.Top="172" Width="122" ManipulationMode="All" />
        </Canvas>
    </Grid>

Public NotInheritable Class MainPage
    Inherits Page

    Dim dragTranslation As New TranslateTransform

    Public Sub New()

        InitializeComponent()

        AddHandler greencircle.ManipulationDelta, AddressOf Me.Drag_ManipulationDelta
        greencircle.RenderTransform = Me.dragTranslation

    End Sub

    Private Sub Drag_ManipulationDelta(sender As Object, e As ManipulationDeltaRoutedEventArgs)
       

        Dim transform = greencircle.TransformToVisual(maincanvas)
        Dim p As Point
        p.X = 0
        p.Y = 0
        Dim point As Point = transform.TransformPoint(p)



        If (maincanvas.Width > (greencircle.Width + point.X + e.Delta.Translation.X) AndAlso (0 < (point.X + e.Delta.Translation.X))) Then
            dragTranslation.X += e.Delta.Translation.X
        End If

        If (maincanvas.Height > (greencircle.Height + point.Y + e.Delta.Translation.Y)) AndAlso (0 < (point.Y + e.Delta.Translation.Y)) Then
            dragTranslation.Y += e.Delta.Translation.Y
        End If


        Dim x As Double = CDbl(greencircle.GetValue(Canvas.LeftProperty))
        Dim y As Double = CDbl(greencircle.GetValue(Canvas.TopProperty))


        e.Handled = True


    End Sub

End Class

Answer 1

Hi imr2k1,

1-I can't find the position (x,y) of the green circle after move

Yes, what you've wrote can only record the initialized position, but not the updated one. see the remark section of LeftProperty property, I suggest you could use point.x and point.y to instead.

        'Dim x As Double = CDbl(greencircle.GetValue(Canvas.LeftProperty))
        Dim x As Double = point.X
        'Dim y As Double = CDbl(greencircle.GetValue(Canvas.TopProperty))
        Dim y As Double = point.Y

2- how can I now if the green circle in side the red one?

Calculate the position is fine, there is no API for hit test, for instance you can calculate if the border of the green circle include in the red circle.

--James

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Answer 2

thanks it worked fine.

for part 2 i found this : point inside circle