Flutter input formatting in textformfield

Question

I'm trying to format textformfield while typing. I've managed to get it working...well sort of. Currently the textformfield takes in number and works like this:

user types in number for example "1" - > user types in second number ex. "2" the formatting changes the value to "1.2" by adding. in between -> user types in a third number "3" the formatting changes the value to "12.3".

Now my issue is that this is a price field and I want to round up to two digits after the. SO it would be 1.00, 1.20 or 12.30.

I've been sitting on this for a bit now and I have no idea how to make it work.

I want to make sure that there cannot be more than 5 characters inside with largest value example (12.30)

The Code:

TextFormField(
                  validator: (fuelPriceValue) {
                    if (fuelPriceValue!.isEmpty) {
                      return null;
                    }
                  },
                  onChanged: (fuelPriceValue) {
                    fuelPrice = (fuelPriceValue as TextEditingController);
                  },
                  controller: fuelPrice,
                  keyboardType: TextInputType.number,
                  inputFormatters: [
                    LengthLimitingTextInputFormatter(4),
                    FilteringTextInputFormatter.allow(RegExp(r'\d*')),
                    TextInputFormatter.withFunction((oldValue, newValue) {
                      LengthLimitingTextInputFormatter(3);
                      if (newValue.text.length == 2) {
                        return TextEditingValue(
                            text: '${newValue.text.substring(0, 1)}.${newValue.text.substring(1)}',
                            selection: TextSelection.fromPosition(TextPosition(offset: newValue.text.length + 1))
                        );
                      }
                      LengthLimitingTextInputFormatter(4);
                      if (newValue.text.length == 3) {
                        return TextEditingValue(
                            text: '${newValue.text.substring(0, 2)}.${newValue.text.substring(2)}',
                            selection: TextSelection.fromPosition(TextPosition(offset: newValue.text.length + 1))
                        );
                      }
                      if (newValue.text.length == 4) {
                        return TextEditingValue(
                            text: '${newValue.text.substring(0, 2)}.${newValue.text.substring(2)}',
                            selection: TextSelection.fromPosition(TextPosition(offset: newValue.text.length))
                        );
                      }
                      return TextEditingValue(
                        text: newValue.text,
                        selection: TextSelection.collapsed(offset: newValue.text.length),
                      );
                    }),
                  ],
                  // inputFormatters: [
                  //   LengthLimitingTextInputFormatter(5),
                  //   FilteringTextInputFormatter.allow(RegExp(r'\d*')),
                  //   TextInputFormatter.withFunction((oldValue, newValue) {
                  //
                  //     LengthLimitingTextInputFormatter(3);
                  //     if (newValue.text.length == 2) {
                  //       return TextEditingValue(
                  //           text: '${newValue.text.substring(0, 1)}.${newValue.text.substring(1)}',
                  //           selection: TextSelection.fromPosition(TextPosition(offset: newValue.text.length + 1))
                  //       );
                  //     }
                  //     LengthLimitingTextInputFormatter(4);
                  //     if (newValue.text.length == 3) {
                  //       return TextEditingValue(
                  //           text: '${newValue.text.substring(0, 2)}.${newValue.text.substring(2)}',
                  //           selection: TextSelection.fromPosition(TextPosition(offset: newValue.text.length + 1))
                  //       );
                  //     }
                  //     if (newValue.text.length == 4) {
                  //       return TextEditingValue(
                  //           text: '${newValue.text.substring(0, 2)}.${newValue.text.substring(2)}',
                  //           selection: TextSelection.fromPosition(TextPosition(offset: newValue.text.length))
                  //       );
                  //     }
                  //     return TextEditingValue(
                  //       text: newValue.text,
                  //       selection: TextSelection.collapsed(offset: newValue.text.length),
                  //     );
                  //   }),
                  // ],
                  decoration: InputDecoration(
                      errorBorder: OutlineInputBorder(),
                      border: OutlineInputBorder(),
                      contentPadding: EdgeInsets.only(left: 10))),

Answer 1

its just idea not final solution.

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class TextExample extends StatefulWidget {
  const TextExample({super.key});

  @override
  State<TextExample> createState() => _TextExampleState();
}

class _TextExampleState extends State<TextExample> {
  TextEditingController c = TextEditingController();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Container(
          child: Column(
            children: [
              TextFormField(
                controller: c,
                onChanged: (value) {
                  //TextSelection.fromPosition(TextPosition(offset: c.text.length));
                },
                keyboardType: TextInputType.number,
                inputFormatters: [
                  LengthLimitingTextInputFormatter(4),
                  FilteringTextInputFormatter.allow(RegExp(r"[0-9.]")),
                  TextInputFormatter.withFunction((oldValue, newValue) {
                  String input = newValue.text;
                  if(input.length==2){
                    if(!input.contains(".")){
                      input = input[0] + "."+input[1];
                    }else{
                    }
                  }
                  if(input.length==3){
                    if(input.contains(".")){
                      input = input.replaceAll(".", "");
                      input = input[0] + "."+input[1];
                    }else{
                    }
                  }
                  if(input.length==4){
                    var count = '.'.allMatches(input).length;
                    if(count>1){
                      input = oldValue.text;
                      return upr(input);
                    }else if(count==1){
                      if(input.contains(".") && input.length==4){
                        // var position = input.indexOf('.');
                        input = input.replaceAll(".", "");
                        input = input[0] + input[1]+"."+input[2];
                        if(int.parse(input[0]) != 1){
                          input = oldValue.text;
                          return upr(input);
                        }
                        if(int.parse(input[0]) == 1 && int.parse(input[1])>2 ){
                          input = oldValue.text;
                          return upr(input);
                        }
                        if(int.parse(input[0]) == 1 && int.parse(input[1])<3 && int.parse(input[3])>3){
                          input = oldValue.text;
                          return upr(input);
                        }
                        if(int.parse(input[0]) != 1 && int.parse(input[1])< 3 ){
                          input = oldValue.text;
                          return upr(input);
                        }
                      }

                    }else{
                      input = oldValue.text;
                      return upr(input);
                    }
                  }
                  if(input.length>4){
                     input = oldValue.text;
                     return upr(input);
                  }
                  return upr(input);
                  }),
                ],
              ),
            ],
          ),
        ),
      ),
    );
  }
}
TextEditingValue upr(input){
    TextEditingValue  val1 = TextEditingValue(
      text:input,
      selection: TextSelection.fromPosition(TextPosition(offset: input.length))
      );
    return val1 ;
}

Answer 2

Ok so I've managed to answer the question myself. THank you for suggestions.

Here is the updated code:

In my widget class I've added

final RegExp regExp = new RegExp(r'^\d{2}\.\d{2}$');

And here is the inputFormatter from textformfield

inputFormatters: [
                      new LengthLimitingTextInputFormatter(6),

                      FilteringTextInputFormatter.allow(RegExp(r'\d*')),
                      TextInputFormatter.withFunction((oldValue, newValue) {
                        if (newValue.text.length == 1 && newValue.text.length > oldValue.text.length) {
                          return TextEditingValue(
                              text: '${newValue.text}.00',
                              selection: TextSelection.fromPosition(TextPosition(offset: newValue.text.length + 3))
                          );
                        }
                        if (newValue.text.length == 4) {
                          return TextEditingValue(
                              text: '${newValue.text.substring(0, 1)}.${newValue.text.substring(3)}0',
                              selection: TextSelection.fromPosition(TextPosition(offset: newValue.text.length + 1))
                          );
                        }
                        LengthLimitingTextInputFormatter(5);
                        if (newValue.text.length == 5) {
                            if (!regExp.hasMatch(oldValue.text)) {
                              return TextEditingValue(
                                  text: '${newValue.text.substring(0, 1)}${newValue.text.substring(
                                      3, 4)}.${newValue.text.substring(4)}0',
                                  selection: TextSelection.fromPosition(
                                      TextPosition(offset: newValue.text.length))
                              );
                            } else {
                              return  TextEditingValue(
                                  text: oldValue.text,
                                  selection: TextSelection.fromPosition(
                                      TextPosition(offset: newValue.text.length))
                              );
                            }
                        }
                        return TextEditingValue(
                          text: newValue.text,
                          selection: TextSelection.collapsed(offset: newValue.text.length),
                        );
                      }),
                    ],