Android Question ClsExplorer error in B4XMainPage

Sub EXPLORER_Click
    dlgFileExpl.Initialize(Activity, "/mnt", ".shp,.drn", True, False, "OK")   <==== Activity/B4XMainPage === Descripción del error: Variable 'activity' no declarada... 
    dlgFileExpl.DialogRect.Left = 25dip
    dlgFileExpl.DialogRect.Right = 100%x - 25dip
    dlgFileExpl.DialogRect.Top =0 'btnMnt.Top + btnMnt.Height
    dlgFileExpl.DialogRect.Bottom = 95%y
    dlgFileExpl.BackgroundColor = Colors.LightGray
    dlgFileExpl.BorderColor = Colors.RGB(128, 128, 128)
    dlgFileExpl.FastScrollEnabled = True
    dlgFileExpl.FolderTextColor = Colors.Black
    dlgFileExpl.FileTextColor1 = Colors.Blue
    dlgFileExpl.FileTextColor2 = Colors.White
    dlgFileExpl.DividerColor = Colors.Gray
    dlgFileExpl.Explorer
    If Not(dlgFileExpl.Selection.Canceled Or dlgFileExpl.Selection.ChosenFile = "") Then
        Msgbox("File:" & CRLF & dlgFileExpl.Selection.ChosenPath & "/" & dlgFileExpl.Selection.ChosenFile, "Your choice")
    
        SHPREADER(dlgFileExpl.Selection.ChosenFile)
 
    End If
End Sub