System.IOUtils.TPath.GetDocumentsPath + System.SysUtils.PathDelim + 'myfile';

PathDelim VS DirectorySeparatorChar

System.SysUtils.PathDelim was introduced in Delphi 6 / Kylix 1, as a means to enable the writing of platform independent code. The introduction of Kylix, the original Delphi Linux compiler, meant that for the first time Delphi code executed on a *nix platform, as well as its original target of Windows.
System.IOUtils.TPath.DirectorySeparatorChar is part of the IOUtils unit that was introduced more recently to support the current wave of cross-platform tooling, which supports MacOS, iOS, Android and will soon encompass Linux once more.
Where you have a choice between System.SysUtils and System.IOUtils, you are generally expected to use the latter. The System.IOUtils is the cross-platform unit for file system support. That said, you commonly would not use DirectorySeparatorChar directly, but instead would use methods like System.IOUtils.TPath.Combine.
--David Heffernan

http://androidcookie.com/android-firemonkey.html

Delphi Login Form Code

https://www.thoughtco.com/display-a-login-password-dialog-1058469

delphi android background application

Functions and procedures

http://www.delphibasics.co.uk/Article.asp?Name=Routines

Delphi - how to get a list of all files of directory

Var
  Path    : String;
  SR      : TSearchRec;
  DirList : TStrings;
begin
  if OpenPictureDialog1.Execute then
  begin
    Path:=ExtractFileDir(OpenPictureDialog1.FileName); //Get the path of the selected file
    DirList:=TStringList.Create;
    try
          if FindFirst(Path + '*.*', faArchive, SR) = 0 then
          begin
            repeat
                DirList.Add(SR.Name); //Fill the list
            until FindNext(SR) <> 0;
            FindClose(SR);
          end;

     //do your stuff

    finally
     DirList.Free;
    end;
  end;

end;