Android Question Howto get a Firebase Storage's file public https:-URL?

Sub btnDownloadPublic_Click
   Wait For (GetDownloadUrl("/public/Untitled.png")) Complete (Url As String)
   If Url <> "" Then
     Log(Url)
   End If
End Sub

Sub GetDownloadUrl(ServerPath As String) As ResumableSub
   Dim fs As JavaObject = Starter.storage
   fs = fs.GetField("fs")
   Dim ref As JavaObject = fs.RunMethod("getReferenceFromUrl", Array(Starter.bucket & ServerPath))
   Dim task As JavaObject = ref.RunMethod("getDownloadUrl", Null)
   Do While task.RunMethod("isComplete", Null) = False
     Sleep(100)
   Loop
   If task.RunMethod("isSuccessful", Null) Then
     Dim s As String = task.RunMethod("getResult", Null)
     Return s
   Else
     Log("Error")
     Return ""
   End If
End Sub

...
      wait for (GetDownloadUrl(ServerPath)) complete (strDownloadUrlHttps As String)
      If strDownloadUrlHttps.Length > 0 Then

          wait for(ShortenUrl(strDownloadUrlHttps)) complete (strUrlShort As String)
          Log( strUrlShort )

      End If
...

Sub ShortenUrl(url As String) As ResumableSub
    Dim j As HttpJob
    j.Initialize("shortenurl", Me)
    Dim jg As JSONGenerator
    jg.Initialize(CreateMap("longUrl": url))
    ' Google API key is awailable here --> https://console.developers.google.com/apis/api/urlshortener.googleapis.com/overview?project=yyyyyyyyyyyyyyyyyyyyyyyyyy
    '  (don't forget to ENABLE)
    j.PostBytes($"https://www.googleapis.com/urlshortener/v1/url?key=${Starter.apikey}"$, jg.ToString.GetBytes("UTF8"))
    j.GetRequest.SetContentType("application/json")
    wait for JobDone(job As HttpJob)
    Dim shortUrl As String = ""
    If job.JobName = "shortenurl" Then
        If job.Success Then
            Dim jp As JSONParser
            jp.Initialize(job.GetString)
            shortUrl = jp.NextObject.Get("id")
        Else
            Log("Error: " & job.ErrorMessage)
        End If
    End If
    job.Release
    Return shortUrl
End Sub

Sub ShortenUrl(url As String) As ResumableSub
    Dim j As HttpJob
    j.Initialize("", Me)
    Dim jg As JSONGenerator
    jg.Initialize(CreateMap("longUrl": url))
    ' Google API key is awailable here --> https://console.developers.google.com/apis/api/urlshortener.googleapis.com/overview?project=yyyyyyyyyyyyyyyyyyyyyyyyyy
    '  (don't forget to ENABLE)
    j.PostBytes($"https://www.googleapis.com/urlshortener/v1/url?key=${Starter.apikey}"$, jg.ToString.GetBytes("UTF8"))
    j.GetRequest.SetContentType("application/json")
    wait for (j) JobDone(job As HttpJob)
    Dim shortUrl As String = ""
        If job.Success Then
            Dim jp As JSONParser
            jp.Initialize(job.GetString)
            shortUrl = jp.NextObject.Get("id")
        Else
            Log("Error: " & job.ErrorMessage)
        End If
    job.Release
    Return shortUrl
End Sub