shopping_cart_tab.dart

class _ShoppingCartTabState extends State<ShoppingCartTab> {
  // ...

Widget _buildDateAndTimePicker(BuildContext context) { // NEW FROM HERE
 return Column(
   children: <Widget>[
     Row(
       mainAxisAlignment: MainAxisAlignment.spaceBetween,
       children: <Widget>[
         Row(
           mainAxisAlignment: MainAxisAlignment.start,
           children: const <Widget>[
             Icon(
               CupertinoIcons.clock,
               color: CupertinoColors.lightBackgroundGray,
               size: 28,
             ),
             SizedBox(width: 6),
             Text(
               'Delivery time',
               style: Styles.deliveryTimeLabel,
             ),
           ],
         ),
         Text(
           DateFormat.yMMMd().add_jm().format(dateTime),
           style: Styles.deliveryTime,
         ),
       ],
     ),
     Container(
       height: _kDateTimePickerHeight,
       child: CupertinoDatePicker(
         mode: CupertinoDatePickerMode.dateAndTime,
         initialDateTime: dateTime,
         onDateTimeChanged: (newDateTime) {
           setState(() {
             dateTime = newDateTime;
           });
         },
       ),
     ),
   ],
 );
}                                                // TO HERE

SliverChildBuilderDelegate _buildSliverChildBuilderDelegate(
   AppStateModel model) {
  // ...