样品：

class mycard extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Container(
      child: new Card(
        child: new Center(
          child: new Icon(
            Icons.refresh,size: 150.0,),decoration: new BoxDecoration(BoxShadow: [
        new BoxShadow(
          color: Colors.black,blurRadius: 20.0,]),);
  }
}