Android Question How to check file size before downloading it

Sub Activity_Create(FirstTime As Boolean)
   If FirstTime Then
     hc.Initialize("hc")
   End If
   Dim req As HttpRequest
   req.InitializeHead("http://www.openandromaps.org/maps/europe/Malta.zip")
   hc.Execute(req, 1)
End Sub

Sub hc_ResponseSuccess (Response As HttpResponse, TaskId As Int)
   Log("File size: " & Response.ContentLength)
   Response.Release
End Sub

Sub hc_ResponseError (Response As HttpResponse, Reason As String, StatusCode As Int, TaskId As Int)
   Log("error: " & StatusCode)
   Response.Release
End Sub

Log(Response.GetHeaders)
Dim cl As List = Response.GetHeaders.Get("Content-Length")
If cl.Size > 0 Then Log(cl.Get(0))

Sub hc_ResponseSuccess (Response As HttpResponse, TaskId As Int)
  Response.Release
End Sub

Sub hc_ResponseError (Response As HttpResponse, Reason As String, StatusCode As Int, TaskId As Int)
  Response.Release
End Sub

#Region  Project Attributes
    #ApplicationLabel: B4A Example
    #VersionCode: 1
    #VersionName:
    'SupportedOrientations possible values: unspecified, landscape or portrait.
    #SupportedOrientations: unspecified
    #CanInstallToExternalStorage: False
#End Region

#Region  Activity Attributes
    #FullScreen: False
    #IncludeTitle: True
#End Region

Sub Process_Globals
    'These global variables will be declared once when the application starts.
    'These variables can be accessed from all modules.
    Dim hc As HttpClient
End Sub

Sub Globals
    'These global variables will be redeclared each time the activity is created.
    'These variables can only be accessed from this module.

End Sub

Sub Activity_Create(FirstTime As Boolean)
    'Do not forget to load the layout file created with the visual designer. For example:
    Activity.LoadLayout("Layout1")
    If FirstTime Then
       hc.Initialize("hc")
    End If
    Dim req As HttpRequest
    req.InitializeHead("http://www.openandromaps.org/maps/europe/Romania.zip")
    hc.Execute(req, 1)
End Sub

Sub Activity_Resume

End Sub

Sub Activity_Pause (UserClosed As Boolean)

End Sub

Sub hc_ResponseSuccess (Response As HttpResponse, TaskId As Int)
  'Log("File size: " & Response.ContentLength)
  Response.Release
End Sub

Sub hc_ResponseError (Response As HttpResponse, Reason As String, StatusCode As Int, TaskId As Int)
  'Log("error: " & StatusCode)
  Response.Release
End Sub