B4J Question Tracking the position of an animation

Sub Process_Globals
 Private fx As JFX
 Private MainForm As Form
 Dim iv As ImageView
 Dim im As Image
End Sub
Sub AppStart (Form1 As Form, Args() As String)
 MainForm = Form1
 MainForm.Show
 im.Initialize("","c:/temp/hannah.jpg") ' the image
 iv.Initialize("iv")
 iv.SetImage(im)
 MainForm.RootPane.AddNode(iv,10,10,100,100)
 Dim jo As JavaObject = iv ' the imageview
 Dim o As Object = jo.CreateEvent("javafx.beans.value.ChangeListener","moved",False)
 jo.runmethodJO("layoutXProperty",Null).RunMethod("addListener",Array(o)) ' make sure you choose property that will change
 iv.SetLayoutAnimated(5000,100,300,100,100)
End Sub
Sub moved_Event(MethodName As String, Args() As Object)' ignore the arguments
 Log("X :"&iv.Left&" Y :"&iv.Top)' read the posn from the imageview
End Sub

Sub Button1_Click
   AnimateTo(Button1, 1000, Rnd(0, 500), Rnd(0, 500))
End Sub

Sub AnimateTo(View As B4XView, Duration As Int, TargetX As Int, TargetY As Int)
   If Duration = 0 Then
       View.Left = TargetX
       View.Top = TargetY
       Return
   End If
   Dim StartTime As Long = DateTime.Now
   Dim StartX As Int = View.Left
   Dim StartY As Int = View.Top
   Do While DateTime.Now < StartTime + Duration
       Dim f As Float = (DateTime.Now - StartTime) / Duration
       Dim x As Int = StartX + f * (TargetX - StartX)
       Dim y As Int = StartY + f * (TargetY - StartY)
       View.Left = x
       View.Top = y
'       Log(x & ", " & y)
       Sleep(10)
   Loop
   View.Left = TargetX
   View.Top = TargetY
End Sub