I tried this solution from the other question: How to: add a blank space after every 4 characters when typing in TextFormField and changed only the 4 to 1. But this solution has some issues like here mention: How to: add a blank space after every 4 characters when typing in TextFormField

class CustomInputFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
      TextEditingValue oldValue, TextEditingValue newValue) {
    var text = newValue.text;

    if (newValue.selection.baseOffset == 0) {
      return newValue;
    }

    var buffer = StringBuffer();
    for (int i = 0; i < text.length; i  ) {
      buffer.write(text[i]);
      var nonZeroIndex = i   1;
      if (nonZeroIndex % 1 == 0 && nonZeroIndex != text.length) {
        buffer.write(' ');
      }
    }

    var string = buffer.toString();
    return newValue.copyWith(
        text: string,
        selection: TextSelection.collapsed(offset: string.length));
  }
}

inputFormatters: [CustomInputFormatter()],

CodePudding user response：

You can replace all spaces and add spaces in a loop. Also the last space isn't added so you can delete the values

class CustomInputFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) {
    var text = newValue.text;
print(text);
    if (newValue.selection.baseOffset == 0) {
      return newValue;
    }

    var buffer = StringBuffer();
    text = text.replaceAll(" ", "");
    for (int i = 0; i < text.length; i  ) {
      buffer.write(text[i]);
     if(i < (text.length-1))buffer.write(" ");
    }

    var string = buffer.toString();
    return newValue.copyWith(
        text: string,
        selection: TextSelection.collapsed(offset: string.length)
    );
  }
}