Label with background drawable problem

I have code:

Sub Globals
Dim Label4 As Label
End Sub

Sub Activity_Create(FirstTime As Boolean)
Dim c As Canvas
Dim r As Rect
Dim cd As ColorDrawable
c.Initialize (Label4)
cd.Initialize(Colors.blue, 10dip)
r.Initialize(0, 0, Label4.width, Label4.height)
c.DrawDrawable(cd, r)
End Sub

but the result the text on label was missing and replace it my rectangle
can u help me to fix so my label text still there?

thanks