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

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  late FocusNode nodeReg1;
  late FocusNode nodeReg2;

  @override
  initState() {
    nodeReg1 = FocusNode();
    nodeReg2 = FocusNode();

    nodeReg1.addListener(() {
      if (nodeReg1.hasFocus) {
        nodeReg2.unfocus();
      }
    });
    nodeReg2.addListener(() {
      if (nodeReg2.hasFocus) {
        nodeReg1.unfocus();
      }
    });

    super.initState();
  }

  @override
  void dispose() {
    nodeReg1.dispose();
    nodeReg2.dispose();

    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Center(
                child: SelectableText(
              "This is the first region",
              focusNode: nodeReg1,
              autofocus: true,
            )),
            Center(
                child: SelectableText(
              "This is the second region",
              focusNode: nodeReg2,
              autofocus: true,
            )),
          ],
        ));
  }
}