问如何在颤振中为下拉式滚动条提供填充物？

EN

import 'package:dropdown_button2/dropdown_button2.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:sizer/sizer.dart';

class LocationDropdown extends StatefulWidget {
  final List cities;
  final String? selectedCity;
  final Color? locationIconColor;
  final Color? iconColor;
  final Color? textColor;
  final Function(String?) onLocationChange;
  final double? width;
  final Offset? offset;

  const LocationDropdown({
    Key? key,
    required this.cities,
    required this.selectedCity,
    this.locationIconColor,
    this.iconColor,
    this.textColor,
    this.width,
    this.offset,
    required this.onLocationChange,
  }) : super(key: key);

  @override
  State<LocationDropdown> createState() => _LocationDropdownState();
}

class _LocationDropdownState extends State<LocationDropdown> {
  bool isDropDownButtonClicked = false;

  @override
  Widget build(BuildContext context) {
    return DropdownButtonHideUnderline(
      child: DropdownButton2<String>(
        onMenuStateChange: (value) {
          setState(() {
            isDropDownButtonClicked = value;
          });
        },
        isExpanded: true,
        hint: Row(
          children: [
            SvgPicture.asset(
              Constants.marker,
              height: 16,
              color: widget.locationIconColor,
            ),
            const SizedBox(
              width: 5,
            ),
            SizedBox(
              width: widget.width == null ? null : (widget.width! - 40),
              child: Text(
                "${widget.selectedCity}",
                style: TextStyle(
                  fontSize: 14,
                  color: widget.textColor ?? Colors.white,
                ),
                overflow: TextOverflow.ellipsis,
                maxLines: 1,
              ),
            ),
            const Spacer(),
            RotatedBox(
              quarterTurns: isDropDownButtonClicked ? 2 : 0,
              child: SvgPicture.asset(
                Constants.downward_white_icon,
                width: 15,
                color: widget.iconColor,
              ),
            ),
          ],
        ),
        items: widget.cities
            .map((item) => DropdownMenuItem<String>(
                  value: item,
                  child: Text(
                    "$item",
                    style: TextStyle(
                        fontSize: 14,
                        fontWeight: "Mumbai" == item
                            ? FontWeight.w500
                            : FontWeight.w300,
                        color: widget.selectedCity == item
                            ? ColorCode.secondaryColor
                            : ColorCode.placeholderDefault),
                    overflow: TextOverflow.ellipsis,
                  ),
                ))
            .toList(),
        onChanged: widget.onLocationChange,
        icon: const SizedBox.shrink(),
        buttonElevation: 2,
        itemHeight: 35,
        itemPadding: const EdgeInsets.only(left: 14, right: 14),
        dropdownMaxHeight: 140,
        dropdownWidth: 150,
        dropdownPadding: null,
        dropdownDecoration: BoxDecoration(
          borderRadius: BorderRadius.circular(14),
          color: Theme.of(context).colorScheme.primaryContainer,
        ),
        scrollbarRadius: const Radius.circular(40),
        scrollbarThickness: 2.w,
        scrollbarAlwaysShow: true,
        offset: widget.offset ?? const Offset(0, 0),
      ),
    );
  }
}