TextField does not behave correctly

main.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Text Field'),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  Widget build(BuildContext context) {
     return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: SizedBox(
          width: 250.0,
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              TextFieldHandler(),
              SizedBox(height: 20),
              ElevatedButton(
                child: Text("Print Line"),
                onPressed: () {
                  print("=== === === === ===");
                }
              )
            ]
          )
        ),
      ),
    );
  }
}

class TextFieldHandler extends StatefulWidget {
  
  @override
  TextFieldHandlerState createState() => TextFieldHandlerState();
}

class TextFieldHandlerState extends State<TextFieldHandler> {
  
  TextEditingController _controller;
  int _lastCharacterCount;
  int _textChangesAfter = 0;
  bool _shouldIgnoreNextTextChange = false;
  
  void _onTextChange() {
    if (_shouldIgnoreNextTextChange) {
      _shouldIgnoreNextTextChange = false;
      return;
    }
    
    final text = _controller.text;
    final lastCharacterCount = _lastCharacterCount;
    _lastCharacterCount = text.characters.length;
    
    print("$_textChangesAfter onTextChange '$text'");
    print("$_textChangesAfter - ${_controller.value}");
    
    if (_controller.text.isNotEmpty) {
      _updateText(text, _controller.value, lastCharacterCount);
    }
    
    print("$_textChangesAfter next ${_textChangesAfter + 1}");
    _textChangesAfter++;
  }
  
  void _updateText(String text, TextEditingValue editingValue, int lastCharacterCount) {
    
    print("$_textChangesAfter _update '$text' $lastCharacterCount ${text.characters.length}");
    
    if (lastCharacterCount == 0 && text.characters.length == 1) {
      print("$_textChangesAfter rest to 0");
      _textChangesAfter = 0;
      
      final newText = text + ' ';
      _controller.value = TextEditingValue(
        text: newText,
        selection: TextSelection.collapsed(offset: newText.length),
        composing: TextRange.empty,
      );
    } else if (lastCharacterCount == 2 && text.characters.length == 1) {
      print("$_textChangesAfter rest to 0");
      _textChangesAfter = 0;
      
      _controller.clear();
      _shouldIgnoreNextTextChange = true;
    }
  }
  
  @override
  void initState() {
    super.initState();

    _lastCharacterCount = 0;
    _textChangesAfter = 0;
    _controller = TextEditingController();
    _controller.addListener(_onTextChange);
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }
 
  @override
  Widget build(BuildContext context) {
    return TextField(
      controller: _controller,
      decoration: const InputDecoration(
        hintText: '🐉 Hint',
      ),
    );
  }
}