Application.ProcessMessages

//如果有这样一个循环, 是非常可怕的; 因为它完不了, 你得等着.

procedure TForm1.Button1Click(Sender: TObject);

var

  i: Integer;

begin

  for i := 0 to MaxInt do

  begin

    Text := IntToStr(i);

  end;

end;


 
   




//即使这样也无济于事, 因为在循环期间你执行不了 Button2Click

var

  b: Boolean;



procedure TForm1.Button1Click(Sender: TObject);

var

  i: Integer;

begin

  b := True;

  for i := 0 to MaxInt do

  begin

    if b then Text := IntToStr(i) else Exit;

  end;

end;



procedure TForm1.Button2Click(Sender: TObject);

begin

  b := False;

end;


 
   




//如果在循环期间...

for i := 0 to MaxInt do

  begin

    if b then Text := IntToStr(i) else Exit;

    {看看还有其他什么事情发生}

  end;


 
   




//Application.ProcessMessages 就是干这个的!

var

  b: Boolean;



procedure TForm1.Button1Click(Sender: TObject);

var

  i: Integer;

begin

  b := True;

  for i := 0 to MaxInt do

  begin

    if b then Text := IntToStr(i) else Exit;

    Application.ProcessMessages; {!}

  end;

end;



procedure TForm1.Button2Click(Sender: TObject);

begin

  b := False;

end;