Multiline TextField issue.

main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: ''),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Text Decenders Bug'),
      ),
      body: Container(
        color: Colors.lightGreenAccent,
        child: Scrollbar(
          child: TextField(
            autofocus: true,
            maxLines: 4,
            textCapitalization: TextCapitalization.sentences,
            decoration: InputDecoration.collapsed(
                border: InputBorder.none,
                hintText: "type here please",
                hintStyle: TextStyle(color: Colors.green)),
          ),
        ),
      ),
    );
  }
}