interface

uses
  Classes, SyncObjs,
  Forms, WinXCtrls, StdCtrls, ExtCtrls;

type
  TheThread = class(TThread)
    constructor Create(CreateSuspendet: Boolean);
    destructor Destroy; override;
  private
    FValue: Integer;
  protected
    FCS: TCriticalSection;
    procedure Execute; override;
    function GetValue: Integer;
    procedure SetValue(AValue: Integer);
  public
    property Value: Integer read GetValue write SetValue;
  end;

type
  TMainForm = class(TForm)
    Indicator: TActivityIndicator;
    CounterLabel: TLabel;
    StartThreadBtn: TButton;
    Timer: TTimer;
    procedure StartBtnClick(Sender: TObject);
    procedure DoOnTimer(Sender: TObject);
    procedure DoOnTerminate(Sender: TObject);
  private
    { Private-Deklarationen }
    FThread: TheThread;
  public
    { Public-Deklarationen }
  end;

var
  MainForm: TMainForm;

implementation

{$R *.dfm}

uses
  SysUtils;

// *************************************************
constructor TheThread.Create(CreateSuspendet: Boolean);
begin
  FCS := TCriticalSection.Create;
  inherited;
end;

destructor TheThread.Destroy;
begin
  inherited;
  FCS.Free;
end;

procedure TheThread.Execute;
var
  I: Integer;
begin
  try
    for I := 0 to 100 do
    begin
      Value := I; // MainForm.CounterLabel.Caption
      Sleep(500);
    end;
  except
    // hier Fehlerbehandlung aller Fehler im Thread
  end;
end;

function TheThread.GetValue: Integer;
begin
  FCS.Enter;
  try
    Result := FValue;
  finally
    FCS.Release;
  end;
end;

procedure TheThread.SetValue(AValue: Integer);
begin
  FCS.Enter;
  try
    FValue := AValue;
  finally
    FCS.Release;
  end;
end;

// *************************************************
procedure TMainForm.StartBtnClick(Sender: TObject);
begin
  MainForm.Indicator.Animate := True;
  Timer.Enabled := True;
  // Thread starten
  FThread := TheThread.Create(True);
  FThread.FreeOnTerminate := True;
  FThread.OnTerminate := DoOnTerminate;
  FThread.Resume;
end;

procedure TMainForm.DoOnTimer(Sender: TObject);
begin
  if Assigned(FThread) then
  begin
    MainForm.CounterLabel.Caption := IntToStr(FThread.Value);
  end;
end;

procedure TMainForm.DoOnTerminate(Sender: TObject);
begin
  MainForm.Indicator.Animate := False;
  Timer.Enabled := False;
  FThread := nil;
end;

end.