How to find and open .txt file, add information and save? Inside Android

I'm using Delphi Berlin 10.1. I could not use OpenDialog, it just does not open inside Android.

I searched the root of the android that stays in / storage / emulated / 0 / where I should find a .txt file The same procedure for Desktop Win32 is ok.

I was able to get the file.

procedure TF_form1.FileSearch(PathName, FileName: string; const InDir: boolean);
var
  Rec: TSearchRec;
  path: string;
  LItem: TListViewItem;
begin
  path := IncludeTrailingBackslash(PathName);
  if FindFirst(path + FileName, faAnyFile - faDirectory, Rec) = 0 then
      repeat
        LItem := ListView.Items.Add;
        LItem.Text := path + Rec.Name;
      until FindNext(Rec) <> 0;


  If not InDir then
  begin
    TabControl.TabIndex := 0;
    exit;
  end;

  if FindFirst(path + '*.*', faDirectory, Rec) = 0 then
      repeat
        if ((Rec.Attr and faDirectory) <> 0) and (Rec.Name <> '.') and (Rec.Name <> '..') then
          FileSearch(path + Rec.Name, FileName, true);
      until FindNext(Rec) <> 0;
end;

But I have not been able to use OpenDialog yet. If you have something similar, let me know.