Delphi - Open a file with default Application in under iOS or show App picker

I am trying to open a file with my app. The File is transferred via a Web service and saved in a local Database, BASE64 encoded. When I show the file in my App, I want to use the default Application for that file type. Or at least I want to show an application picker dialog and let the user choose the application to open the File with. What I have so far is this:

procedure Base64StringToFileAndOpen(const base64String: string; Filename: string);
var
  decodedBytes: TBytes;
  filePath: string;
  fileStream: TFileStream;
  interactionController: UIDocumentInteractionController;
  NSU: NSURL;
begin
  // Decode BASE64 string into bytes
  decodedBytes := TNetEncoding.Base64.DecodeStringToBytes(base64String);

  // Determine the file path
  // NSStrToStr(TNSString.Wrap(NSTemporaryDirectory));
  filePath := System.IOUtils.TPath.Combine(System.IOUtils.TPath.GetTempPath, Filename);

  // Save decoded bytes into a file
  fileStream := TFileStream.Create(filePath, fmCreate);
  try
    fileStream.WriteBuffer(decodedBytes[0], length(decodedBytes));
  finally
    fileStream.Free;
  end;

  NSU := TNSURL.Wrap(TNSURL.OCClass.URLWithString(StrToNSStr(PChar(filePath))));
  interactionController := TUIDocumentInteractionController.Wrap(TUIDocumentInteractionController.alloc.init);
  interactionController.setURL(NSU);
  interactionController.setUTI(StrToNSStr('public.data'));
  interactionController.presentOpenInMenuFromRect(CGRectFromRect(TRectF.Empty), SharedApplication.keyWindow.rootViewController.view, true);
end;

When I run that code on the iPhone (iOS), a box like you would normally expect to show up is shown on the end of the Screen. But nothing is in that Screen. No Apps, no Text, nothing. I would expect Apps to appear here that let me open that File. Where is my mistake? I looked for Kastri framework if something useful is implemented there, but there is only a Share Component, but I do not want to share my File I only want to display it in another app.

Can anyone help me out?

Problem was not the Rect. Problem is because of the way iOS handles files and Apps in sandboxes.

https://github.com/emozgun/delphi-ios-file-storage-sharing

emozgun give a great explanation for that Problem and a Solution. Kastri and the ShareItems sample was my way to to go.