unit Unit6;

interface

uses
  System.SysUtils, System.Classes,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TMyThread = class(TThread)

  protected
    procedure Execute; override;
  end;

  TForm6 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    FThread: TMyThread;
    procedure OnMyThreadTerminate(Sender: TObject);
  public
    { Public declarations }
  end;

var
  Form6: TForm6;

implementation

{$R *.dfm}


procedure TForm6.Button1Click(Sender: TObject);
begin
  FThread := TMyThread.Create;
  FThread.OnTerminate := OnMyThreadTerminate;
  FThread.FreeOnTerminate := True;
end;

{ TMyThread }

procedure TMyThread.Execute;
var
  a, b: Integer;
begin
  inherited;
  b := 0;
  a := a div b;
end;

procedure TForm6.OnMyThreadTerminate(Sender: TObject);
var
  ThreadException: Exception;
begin
  // das hier wird im Kontext des Main-Threads automatisch aufgerufen.
  if Assigned(Sender) and (Sender is TThread) then
  begin
    ThreadException := Exception(TThread(Sender).FatalException);
    if Assigned(ThreadException) then
      ShowMessage(ThreadException.Classname + ' : ' + ThreadException.Message);
  end;
end;

end.