VCL线程同步的问题
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TMyThread = class(TThread)
private
procedure SetVisible;
protected
procedure Execute;override;
end;

TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
procedure FormCreate(Sender: TObject);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
FThread: TMyThread;
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

{ TMyThread }

procedure TMyThread.Execute;
begin
Form1.Button2.Visible := True;
//Synchronize(SetVisible);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
Form1.Button2.Visible := False;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
FThread := TMyThread.Create(False);
end;

procedure TMyThread.SetVisible;
begin
Form1.Button2.Visible := True;
end;

end.



上面的代码Button2控件对应的windows对象会在线程结束时，无缘无故被destroy，导致窗口关闭时报错“句柄无效”。

这是为什么？使用同步却不会。

请讲的详细一点。

[解决办法]
我调试了一下，发现Form1.Button2.Visible := True;主要是调用代码：

Delphi(Pascal) code

procedure TControl.SetVisible(Value: Boolean);begin  if FVisible <> Value then  begin    VisibleChanging;    FVisible := Value;    Perform(CM_VISIBLECHANGED, Ord(Value), 0);    RequestAlign;  end;end;