Super.
Suggestion to think about the NinePatchpicture background, like attached (place .png into a "drawable" folder of the "res"), with help of sub:
B4X:
Sub LoadNinePatchDrawable(ImageName As String) As Object
'Gets a 9-patch drawable from the application resources
Dim r As Reflector
Dim package As String
package = r.GetStaticField("anywheresoftware.b4a.BA", "packageName")
Dim ID_Drawable As Int
ID_Drawable = r.GetStaticField(package & ".R$drawable", ImageName)
r.Target = r.GetContext
r.Target = r.RunMethod("getResources")
Return r.RunMethod2("getDrawable", ID_Drawable, "java.lang.int")
End Sub