Exiting Focus from Multiline - Flutter - flutter

Question

I am currently trying to make a page that take notes on my app so I am using the multiline keyboard type to keep track of the text. However, I am having difficulties escaping the focus of the text. Return brings a new line (which I want it to do) but I am unsure as to when I have onSubmit or onEditingComplete because I never actually submit anything using multiline. In addition, tapping outside of the textfield does not exit the focus of the field. Here is the code that I wrote please let me know if you have any recommendations!
import 'package:flutter/material.dart';
class NoteDetail extends StatefulWidget {
#override
_NoteDetailState createState() => _NoteDetailState();
}
class _NoteDetailState extends State<NoteDetail> {
#override
Widget build(BuildContext context) {
final dimensions = MediaQuery.of(context).size;
return LimitedBox(
maxHeight: dimensions.height - 100,
maxWidth: dimensions.width - 100,
child: Column(
children: <Widget>[
SizedBox(
height: dimensions.height * 0.10,
),
TextField(
keyboardType: TextInputType.multiline,
//this allows the text to work with multiple lines
maxLines: null,
//no max lines making it scroll forever
decoration: InputDecoration(
hintText: 'Start taking some notes',
//shows text before the user starts to text
focusedBorder: InputBorder.none,
enabledBorder: InputBorder.none,
errorBorder: InputBorder.none,
disabledBorder: InputBorder.none,
//this removes the border all together
contentPadding:
EdgeInsets.symmetric(horizontal: dimensions.width * 0.1),
//giving the content some padding on the side
),
),
],
),
);
}
}