Can't into Application.OnIdle ?

Please try attach Demo.
unit Main;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs,
  FMX.Controls.Presentation, FMX.StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    procedure FormCreate(Sender: TObject);
  private
    i: Integer;
    procedure DoIdle(Sender: TObject; var Done: Boolean);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.fmx}

procedure TForm1.DoIdle(Sender: TObject; var Done: Boolean);
begin
     Label1.Text := i.ToString;
     Inc(i);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
     i := 0;
     Application.OnIdle := DoIdle;
end;

end.
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