Android Question ExternalStorage Write/Read file

Sub CopyMapToDownload(Folders() As String, Filename As String)
    Dim extfolder As ExternalFile
    Dim extfile As ExternalFile
 
    Storage.SelectDir(True)
    Wait For Storage_ExternalFolderAvailable
 
    Dim mapfound As Boolean = False
    Dim extfolder As ExternalFile = Storage.FindFile(Storage.Root, Folders(0))
    If Folders.Length > 1 Then
        For i = 1 To Folders.Length -1
            extfolder = Storage.FindFile(extfolder, Folders(i))
        Next
    End If
    If extfolder.IsInitialized Then
        Dim extfile As ExternalFile = Storage.FindFile(extfolder, Filename)
        If extfile.IsInitialized Then
            Dim out As OutputStream = File.OpenOutput(File.DirRootExternal, Starter.MapTempDestination, False)
            mapfound = True
        End If
    End If
    If Not (mapfound) Then
        Dim msg As String = "Map " & Filename & " not found!"
        Msgbox2Async(msg, "Missing Map", "OK", "", "", Null, True)
    End If    
End Sub

' Get DocumentDir
    Dim docs As JavaObject = GetDocumentdDir(PersistantUri)
  
    ' Check if Destfolder Test already exists.
    Dim chkTest As ExternalFile = Storage.FindFile(Storage.Root,"Test")
    If chkTest.IsInitialized = False Then
        'create the Folder "Test"
        docs.RunMethod("createDirectory",Array("Test"))
    End If
    ' Search the created Folder in the Storage Rootdir (we need to have a reference to it)
    Dim Test As ExternalFile = Storage.FindFile(Storage.Root,"Test")
  
    ' define destfile
    Dim destfile As ExternalFile = Storage.CreateNewFile(Test,filetocopy)
    ' Create an Outputstream to the destfile
    Dim os As OutputStream = Storage.OpenOutputStream(destfile)
    ' Create an Inputstream from the Sourcefile to copy
    Dim inpstr As InputStream  = File.OpenInput(File.Combine(File.DirRootExternal,"Download/"),filetocopy)
    ' Copy file
    File.Copy2(inpstr,os)
    ' Close Outputstream
    os.Close