线程 Abstract Error

[lynchhei]

环境 D7,最简单的线程，但创建后直接 “Abstract Error”！
代码如下：

var
Form1: TForm1;

implementation

{$R *.dfm}

type
TestThread = class(TThread)
protected
procedure Execute; overload;
end;

procedure TestThread.Execute;
var
i: Integer;
begin
inherited;
for i := 0 to 500000 do
begin
Form1.Canvas.Lock;
Form1.Canvas.TextOut(10, 10, IntToStr(i));
Form1.Canvas.Unlock;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
TestThread.Create(False);
end;

[看那山瞧那水]

overload->override