如何使 ListWheelScrollView 小部件变圆？

如何使ListWheelScrollView小部件变圆，有可能吗？我制作了Container小部件

Container(
 decoration: BoxDecoration(
  color: Colors.amber,
  shape: BoxShape.circle,
 )
),

并在其中放置了一个ListWheelScrollView，理论上列表不应该爬出它的父级并且应该变成圆形吗？接下来，部分标记和照片。

Container(
 decoration: BoxDecoration(
  color: Colors.amber,
  shape: BoxShape.circle,
 ),
 child: Padding(
  padding: const EdgeInsets.symmetric(horizontal: 8.0),
  child: ListWheelScrollView(

   itemExtent: 50, //height / высота
   squeeze: 1.0, //divider / разделитель
   diameterRatio: 2.0, //diameter / сотношение
   offAxisFraction: 0.0, //bias / смещение +to left -to right

   onSelectedItemChanged: (index) {
    setState(() {
     _ara.forEach( (value) => value.isSelected = false );
     _ara[index].isSelected = true;
     _str = '${_ara[index].data}';
    });
   },

   children: <Widget>[
    for(int i=0; i<_ara.length; i++)
     _getItemList(context, i)
   ],

  ),
 ),
),

main.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
  return MaterialApp(
   debugShowCheckedModeBanner: false,
   title: 'Name App',
   theme: ThemeData(
    primarySwatch: Colors.blue,
   ),
   home: Scaffold(
    appBar: AppBar(
     title: Text('Name Page'),
    ),
    body: MyHomePage(),
   ),
  );
 }
}

class MyHomePage extends StatefulWidget {
 @override
 _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

 List< ItemListData<String> > _ara;

 double _height;
 double _width;
 TextStyle _textStyle;

 String _str;

 @override
 void initState() {
  super.initState();

  _ara = _populateData(20);

  _width = double.infinity;
  _height = double.infinity;
  _textStyle = TextStyle(
   color: Colors.white,
   fontSize: 20.0,
   fontWeight: FontWeight.bold,
  );

  _str = '';

 }

 @override
 void dispose() {
  super.dispose();

 }

 void _f1() {
  setState(() {

  });
 }

 //метод возвращает коллекцию, которая была заполнена объектами класса ItemListData<String>
 //method returns a collection which was filled the objects of the cllass ItemListData<String>
 List _populateData(int amount) {
  List< ItemListData<String> > ara = [];
  for(int i = 0; i<amount; ) {
   i++;
   ara.add( ItemListData<String>('$i') );
  }
  return ara;
 }

 //метод возвращает элемент прокручиваемого списка
 //method returns an element of the scrolling list
 //Widget _getItemList(BuildContext context, int index) {}
 Widget _getItemList(_, index) =>
  Container(
   width: _width,
   height: _height,
   color: _ara[index].isSelected ? Colors.pink : Colors.cyan,
   alignment: Alignment.center,
   child: Text(
    '${_ara[index].data}',
    style: _textStyle,
   ),
  );

 @override
 Widget build(BuildContext context) {
  return Column(
   mainAxisSize: MainAxisSize.max,
   mainAxisAlignment: MainAxisAlignment.start,
   children: <Widget>[
    Expanded(
     flex: 1,
     child: Container(
      alignment: Alignment.center,
      child: Text(
       _str,
       style: TextStyle(
        color: Colors.pink,
        fontSize: 36.0
       ),
      ),
     ),
    ),
    Expanded(
     flex: 1,
     child: Container(
      decoration: BoxDecoration(
       color: Colors.amber,
       shape: BoxShape.circle,
      ),
      child: Padding(
       padding: const EdgeInsets.symmetric(horizontal: 8.0),
       child: ListWheelScrollView(

        itemExtent: 50, //height / высота
        squeeze: 1.0, //divider / разделитель
        diameterRatio: 2.0, //diameter / сотношение
        offAxisFraction: 0.0, //bias / смещение +to left -to right

        onSelectedItemChanged: (index) {
         setState(() {
          _ara.forEach( (value) => value.isSelected = false );
          _ara[index].isSelected = true;
          _str = '${_ara[index].data}';
         });
        },

        children: <Widget>[
         for(int i=0; i<_ara.length; i++)
          _getItemList(context, i)
        ],

       ),
      ),
     ),
    ),
   ],
  );
 }
}

//данные, которые будут отображаться в элементе списка
//data which will be shown in the item of the list
class ItemListData<T> {
 bool isSelected = false;
 T data;
 ItemListData(this.data);
}