flutter Column里边Expanded显示太大的问题

              onTap: () {

                showModalBottomSheet(context: context,builder: (ctx)=>new Column(
                  mainAxisSize: MainAxisSize.min,
                  children: <Widget>[

                Expanded(
                      child:MaterialButton(

效果：

将以上代码改为 :

              onTap: () {

                showModalBottomSheet(context: context,builder: (ctx)=>new Column(
                  mainAxisSize: MainAxisSize.min,
                  children: <Widget>[

                ListTile(
                      title:MaterialButton(

效果为 :