how to format or separate textformfield parts in flutter - flutter

Question

i have a text form field i want to separating the text that comes to text form field
let's say user writes 1111111 and output will be 1,111,111
Form(
child: Column(
children: [
TextFormField(
keyboardType: TextInputType.emailAddress,
decoration: InputDecoration(
labelText: 'Email Address',
hintText: 'you#example.com',
),
)
],
),
),

Answer 1

You should use the controller property from the TextFormField class.
You'll need to make your widget a stateful one (we'll need it's dispose method).
Add the controller to your state:
final _textController = TextEditingController();
#override
void dispose() {
super.dispose();
_textController.dispose();
}
Add a listener to your controller to format your input whenever you type:
#override
void initState() {
super.initState();
_textController.addListener(() {
// using Ashok's answer to format the text
final reg_ex = new RegExp(r'(\d{1,3})(?=(\d{3})+(?!\d))');
final matchFunc = (Match match) => '${match[1]},';
final text = _textController.text;
_textController.value = _textController.value.copyWith(
// we need to remove all the ',' from the values before reformatting
// if you use other formatting values, remember to remove them here
text: text.replaceAll(',', '').replaceAllMapped(reg_ex, matchFunc),
// this will keep the cursor on the right as you type in values
selection: TextSelection(
baseOffset: text.length,
extentOffset: text.length,
),
);
});
}
Use the controller within your TextFormField:
TextFormField(
controller: _textController,
keyboardType: TextInputType.emailAddress,
decoration: InputDecoration(
labelText: 'Email Address',
hintText: 'you#example.com',
),
)

Answer 2

RegExp reg_ex = new RegExp(r'(\d{1,3})(?=(\d{3})+(?!\d))');
Function mathFunc = (Match match) => '${match[1]},';
List<String> sample = [
'1111111',
];
sample.forEach((String str) {
String result = str.replaceAllMapped(reg_ex, mathFunc);
print('$str -> $result');
});