import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  static const bool explicitTransparent = false;

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: Scaffold(
        body: Padding(
          padding: EdgeInsets.all(8.0),
          child: Center(
            child: TextField(
              decoration: InputDecoration(
                filled: true,
                fillColor: Color(0xFFBBBBBB),
                enabledBorder: UnderlineInputBorder(
                  borderSide: explicitTransparent //
                      ? BorderSide(style: BorderStyle.none, color: Colors.transparent)
                      : BorderSide(style: BorderStyle.none),
                  borderRadius: BorderRadius.all(Radius.circular(4)),
                  // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ also note here we have border radius on the bottom, vs the top only default
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}