Android Question b4xImageView and Invalidate

Sub Process_Globals
    Private xui As XUI
End Sub

Sub Globals
    Private iv As B4XImageView
    Private pnl As Panel
    Private baseBitmap As B4XBitmap
End Sub

Sub Activity_Create(FirstTime As Boolean)
    Activity.LoadLayout("main")

    ' Base bitmap (for example a background image)
    baseBitmap = xui.LoadBitmap(File.DirAssets, "backround.png")

    iv.Bitmap = baseBitmap
End Sub

Sub pnl_Touch (Action As Int, X As Float, Y As Float)
    If Action = pnl.ACTION_DOWN Then
        AddImage(X, Y)
    End If
End Sub

Sub AddImage(X As Float, Y As Float)
    Dim bmp As B4XBitmap = xui.LoadBitmap(File.DirAssets, "icone.png")

    ' Create a temporary canvas
    Dim c As B4XCanvas
    Dim newBmp As B4XBitmap = xui.CreateBitmap(baseBitmap.Width, baseBitmap.Height)
    c.Initialize(newBmp)

    ' Draw base image
    c.DrawBitmap(baseBitmap, 0, 0, baseBitmap.Width, baseBitmap.Height)

    ' Draw the new image
    c.DrawBitmap(bmp, X - bmp.Width/2, Y - bmp.Height/2, bmp.Width, bmp.Height)

    c.Invalidate

    ' Update the base bitmap
    baseBitmap = newBmp

    ' Show result
    iv.Bitmap = baseBitmap
End Sub