emoji

main.dart

// import 'dart:convert';
// import 'dart:math';

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

const emoji = '💙';
void main() => runApp(const MaterialApp(home: MyHomePage()));

class MyHomePage extends StatefulWidget {
  final int maxLength;
  const MyHomePage({
    super.key,
    this.maxLength = 10,
  });

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  late final TextEditingController _controller;

  @override
  void initState() {
    _controller = TextEditingController();
    super.initState();
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  void addEmoji() {
    final newText = _controller.text + emoji;
    // if (newText.bytesLength > widget.maxLength) {
    //   return;
    // }
    _controller.text = newText;
  }

  @override
  Widget build(context) => Scaffold(
        body: Center(
          child: TextField(
            controller: _controller,
            maxLength: widget.maxLength,
            //inputFormatters: [Utf8LengthInputFormatter(widget.maxLength)],
            //buildCounter: CounterBuilderDelegate(controller: _controller),
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: addEmoji,
          child: const Icon(Icons.add),
        ),
      );
}

// extension StringByteLenghtX on String {
//   int get bytesLength => const Utf8Encoder().convert(this).length;
// }

// extension IterableStringByteLenghtX on Iterable<String> {
//   int get bytesLength => join().bytesLength;
// }

// extension TextEditingValueTruncateX on TextEditingValue {
//   TextEditingValue truncate(int maxLenght) {
//     if (maxLenght < 1) {
//       return const TextEditingValue();
//     }
//     if (text.bytesLength <= maxLenght) {
//       return this;
//     }

//     final chars = <String>[];

//     for (final char in text.characters) {
//       final lenght = chars.bytesLength + char.bytesLength;
//       if (lenght <= maxLenght) {
//         chars.add(char);
//       }
//     }

//     final truncated = chars.join();

//     return TextEditingValue(
//       text: truncated,
//       selection: selection.copyWith(
//         baseOffset: min(selection.start, truncated.length),
//         extentOffset: min(selection.end, truncated.length),
//       ),
//       composing: TextRange.empty,
//     );
//   }
// }

// class Utf8LengthInputFormatter extends TextInputFormatter {
//   final int maxLength;
//   final bool keepOldValue;

//   Utf8LengthInputFormatter(
//     this.maxLength, {
//     this.keepOldValue = false,
//   });

//   @override
//   TextEditingValue formatEditUpdate(
//     TextEditingValue oldValue,
//     TextEditingValue newValue,
//   ) {
//     if (newValue.text.bytesLength <= maxLength) {
//       return newValue;
//     }

//     if (keepOldValue && oldValue.text.bytesLength <= maxLength) {
//       return oldValue;
//     }
//     return newValue.truncate(maxLength);
//   }
// }

// class CounterBuilderDelegate {
//   final TextEditingController controller;
//   const CounterBuilderDelegate({
//     required this.controller,
//   });
//   Widget call(
//     BuildContext context, {
//     required int currentLength,
//     required bool isFocused,
//     required int? maxLength,
//   }) =>
//       Text(
//         '${controller.text.bytesLength}/$maxLength',
//         style: Theme.of(context).textTheme.caption,
//       );
// }