طريقة اسعمال ال Column في  flutter

Widget build(BuildContext context) {
     return  Scaffold(
       body:  Center(
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.stretch,
           mainAxisAlignment: MainAxisAlignment.center,
           children: [
             Container(width: 50, height: 50, color: Colors.red),
             Container(width: 50, height: 50, color: Colors.white),
             Container(width: 50, height: 50, color: Colors.black),
           ],
         ),
       ),
  );
}