Flutter FocusNodes and TextFields

main.dart

import 'package:flutter/material.dart';

class FocusTextFieldScreen extends StatefulWidget {
  @override
  _FocusTextFieldScreenState createState() => _FocusTextFieldScreenState();
}

class _FocusTextFieldScreenState extends State<FocusTextFieldScreen> {
  FocusNode textField1FocusNode = FocusNode();
  FocusNode textField2FocusNode = FocusNode();
  FocusNode textField3FocusNode = FocusNode();
  late TextEditingController _controller1;
  late TextEditingController _controller2;
  late TextEditingController _controller3;

  String focusedTextField = "None";

  @override
  void initState() {
    super.initState();
    _controller1 = TextEditingController();
    _controller2 = TextEditingController();
    _controller3 = TextEditingController();

    textField1FocusNode.addListener(_onFocusChange);
    textField2FocusNode.addListener(_onFocusChange);
    textField3FocusNode.addListener(_onFocusChange);
  }

  @override
  void dispose() {
    textField1FocusNode.dispose();
    textField2FocusNode.dispose();
    textField3FocusNode.dispose();
    _controller1.dispose();
    _controller2.dispose();
    _controller3.dispose();
    
    super.dispose();
  }

  void _onFocusChange() {
    setState(() {
      if (textField1FocusNode.hasFocus) {
        focusedTextField = "TextField 1";
      } else if (textField2FocusNode.hasFocus) {
        focusedTextField = "TextField 2";
      } else if (textField3FocusNode.hasFocus) {
        focusedTextField = "TextField 3";
      } else {
        focusedTextField = "None";
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Focus Tracking')),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          children: <Widget>[
            TextField(
              focusNode: textField1FocusNode,
              controller: _controller1,
              decoration: InputDecoration(labelText: 'TextField 1'),
            ),
            TextField(
              focusNode: textField2FocusNode,
              controller: _controller2,
              decoration: InputDecoration(labelText: 'TextField 2'),
            ),
            TextField(
              focusNode: textField3FocusNode,
              controller: _controller3,
              decoration: InputDecoration(labelText: 'TextField 3'),
            ),
            SizedBox(height: 20),
            Text('Focused TextField: $focusedTextField'),
          ],
        ),
      ),
    );
  }
}