Remove Empty Space between Text and Trailer Icon of DropdownButton

Question

I have a dropdown that display a list of strings. The values of the strings contain words that only consists of four letters and words that consists of many letters. This gives a layout problem when the selected item is the one with four letters. An empty or white space can be seen between the text and the trailing icon of the dropdown button. How can this be empty space be removed? How do I adjust the size of the dropdown button depending on the value selected?

Photo of Empty Space between text and trailing icon:

List:

List<String> textList = ["test", "this_is_a_long_text"];

Dropdown:

DropdownButtonHideUnderline(
      child: ButtonTheme(
       alignedDropdown: true,
       child: DropdownButton<String>(
        items: textList.map((String dropDownStringItem) {
           return DropdownMenuItem<String>(
                      value: dropDownStringItem,
                      child: Text(dropDownStringItem),
                    );
                  }).toList(),
              onChanged: (String newValueSelected) {
                _onDropDownItemSelected(newValueSelected);
              },
              value: _currentItemSelected,
            ),
          )),

Answer 1

as an option you can build it based on PopupMenuButton instead of regular DropdownButton

below an example

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(child: AwesomeDropdown()),
      ),
    );
  }
}

class AwesomeDropdown extends StatefulWidget {
  @override
  _AwesomeDropdownState createState() => _AwesomeDropdownState();
}

class _AwesomeDropdownState extends State<AwesomeDropdown> {
  final List<String> textList = ["test", "this_is_a111111_long_text"];
  String _currentItemSelected;

  @override
  void initState() {
    super.initState();
    _currentItemSelected = textList[0];
  }

  @override
  Widget build(BuildContext context) {
    return PopupMenuButton<String>(
      itemBuilder: (context) {
        return textList.map((str) {
          return PopupMenuItem(
            value: str,
            child: Text(str),
          );
        }).toList();
      },
      child: Row(
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          Text(_currentItemSelected),
          Icon(Icons.arrow_drop_down),
        ],
      ),
      onSelected: (v) {
        setState(() {
          print('!!!===== $v');
          _currentItemSelected = v;
        });
      },
    );
  }
}