Flutter: Using NumberFormat in TextInputFormatter

This is because after you format the value you are adding a new char but the text selection remains at the same position, one char less, this cause an expected behavior

You can modify your TextInputFormatter like this:

Fixed to support all locales and to remember cursor position

class NumericTextFormatter extends TextInputFormatter {  @override  TextEditingValue formatEditUpdate(      TextEditingValue oldValue, TextEditingValue newValue) {    if (newValue.text.isEmpty) {      return newValue.copyWith(text: '');    } else if (newValue.text.compareTo(oldValue.text) != 0) {      final int selectionIndexFromTheRight =          newValue.text.length - newValue.selection.end;      final f = NumberFormat("#,###");      final number =          int.parse(newValue.text.replaceAll(f.symbols.GROUP_SEP, ''));      final newString = f.format(number);      return TextEditingValue(        text: newString,        selection: TextSelection.collapsed(            offset: newString.length - selectionIndexFromTheRight),      );    } else {      return newValue;    }  }}

Based on the answer and for people from Europe looking for a quick fix

class NumericTextFormatter extends TextInputFormatter {  @override  TextEditingValue formatEditUpdate(      TextEditingValue oldValue, TextEditingValue newValue) {    final currencySymbol = '€';    if (newValue.text.isEmpty || newValue.text.trim() == currencySymbol) {      return newValue.copyWith(text: '');    } else if (newValue.text.compareTo(oldValue.text) != 0) {      var selectionIndexFromTheRight =          newValue.text.length - newValue.selection.end;      final f =          NumberFormat.currency(locale: 'de', decimalDigits: 0, symbol: '');      var num = int.parse(newValue.text.replaceAll(RegExp('[^0-9]'), ''));      final newString = '$currencySymbol ' + f.format(num).trim();      return TextEditingValue(        text: newString,        selection: TextSelection.collapsed(            offset: newString.length - selectionIndexFromTheRight),      );    } else {      return newValue;    }  }}