Flutter force reformat input - flutter

Question

By setting _mytexteditingcontroller.value , We can update value of TextField, But inputFormatters is not running
How can I force inputFormatters to reformat value?
Here is a minimal example , I use LengthLimitingTextInputFormatter(3) to limit length of input, by running _controller.text = '12345678' I want to tell flutter to reformat input again
CONSIDER THAT IT IS A MININAL EXAMPLE, DONT TELL ME USE SUBSTRING TO FIX IT
/// Flutter code sample for TextField
// This sample shows how to get a value from a TextField via the [onSubmitted]
// callback.
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() => runApp(MyApp());
/// This is the main application widget.
class MyApp extends StatelessWidget {
static const String _title = 'Flutter Code Sample';
#override
Widget build(BuildContext context) {
return MaterialApp(
title: _title,
home: MyStatefulWidget(),
);
}
}
/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
MyStatefulWidget({Key key}) : super(key: key);
#override
_MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}
/// This is the private State class that goes with MyStatefulWidget.
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
TextEditingController _controller;
void initState() {
super.initState();
_controller = TextEditingController();
}
void dispose() {
_controller.dispose();
super.dispose();
}
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Column(
children: [
RaisedButton(
child: Text('Set Text'),
onPressed: () {
_controller.text = '12345678';
}),
TextField(
controller: _controller,
inputFormatters: [
LengthLimitingTextInputFormatter(3),
],
onSubmitted: (String value) async {
await showDialog<void>(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: const Text('Thanks!'),
content: Text('You typed "$value".'),
actions: <Widget>[
FlatButton(
onPressed: () {
Navigator.pop(context);
},
child: const Text('OK'),
),
],
);
},
);
},
),
],
),
),
);
}
}

Answer 1

As mentioned above this is a currently open known issue https://github.com/flutter/flutter/issues/30369. However you may try using an extension on TextInputFormatter to achieve a similar result.
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
final Color darkBlue = Color.fromARGB(255, 18, 32, 47);
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
static const String _title = 'Flutter Code Sample';
#override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
debugShowCheckedModeBanner: false,
title: _title,
home: MyStatefulWidget(),
);
}
}
class MyStatefulWidget extends StatefulWidget {
MyStatefulWidget({Key key}) : super(key: key);
#override
_MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
TextEditingController _controller;
void initState() {
super.initState();
_controller = TextEditingController();
}
void dispose() {
_controller.dispose();
super.dispose();
}
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Column(
children: [
RaisedButton(
child: Text('3 Length Limit'),
onPressed: () {
_controller.text = LengthLimitingTextInputFormatter(3).format('12345678');
}),
RaisedButton(
child: Text('Upper case'),
onPressed: () {
_controller.text = UpperCaseTextFormatter().format('upper');
}),
RaisedButton(
child: Text('Length Limit & Upper chained'),
onPressed: () {
_controller.text = LengthLimitingTextInputFormatter(3).format(UpperCaseTextFormatter().format('upper'));
}),
TextField(
controller: _controller,
inputFormatters: [
LengthLimitingTextInputFormatter(3),
UpperCaseTextFormatter(),
],
),
],
),
),
);
}
}
extension on TextInputFormatter {
String format(String text) {
return formatEditUpdate(
const TextEditingValue(),
TextEditingValue(
text: text,
selection: TextSelection(
extentOffset: text.length,
baseOffset: text.length,
),
),
).text;
}
}
class UpperCaseTextFormatter extends TextInputFormatter {
#override
TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) {
return TextEditingValue(
text: newValue.text?.toUpperCase(),
selection: newValue.selection,
);
}
}