Listen to TextSelection changes - flutter

Question

I would like to listen to the changes of the cursor in the textEditingController, but at the moment listener only reacts to the addition and removal of characters, are there any options to get around this?
For example in TextField with [phone] if user set cursor before '+7 ' i want set cursor back to position = 3

Answer 1

I'm not sure, but is this what you want to do?
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return const MaterialApp(
title: 'Demo',
home: MyHomePage(title: 'Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
final TextEditingController _controller = TextEditingController();
#override
void initState() {
super.initState();
_controller.addListener(_setPos3);
}
#override
void dispose() {
_controller.dispose();
super.dispose();
}
void _setPos3() {
if (_controller.selection.baseOffset == 0 &&
_controller.selection.extentOffset == 0 &&
3 <= _controller.text.length) {
_controller.value = _controller.value.copyWith(
selection: const TextSelection(baseOffset: 3, extentOffset: 3),
);
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: TextFormField(
controller: _controller,
),
),
);
}
}