main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Text Field Focus',
      home: MyCustomForm(),
    );
  }
}

// Define a custom Form widget.
class MyCustomForm extends StatefulWidget {
  @override
  _MyCustomFormState createState() => _MyCustomFormState();
}

// Define a corresponding State class.
// This class holds data related to the form.
class _MyCustomFormState extends State<MyCustomForm> {
  // Define the focus node. To manage the lifecycle, create the FocusNode in
  // the initState method, and clean it up in the dispose method.
  FocusNode myFocusNode;

  @override
  void initState() {
    super.initState();

    myFocusNode = FocusNode();
  }

  @override
  void dispose() {
    // Clean up the focus node when the Form is disposed.
    myFocusNode.dispose();

    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Text Field Focus'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          children: [
            Container(
              padding: EdgeInsets.symmetric(vertical: 10.0),
              child: Align(
                alignment: Alignment.centerLeft,
                
                child: Text(
              'Personal Information',
              style: TextStyle(fontWeight: FontWeight.bold),
            ),
              ),
            ),
            
            // The first text field is focused on as soon as the app starts.
            TextFormField(
              autofocus: true,
              decoration: InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'First Name',
              ),
            ),
            // The second text field is focused on when a user taps the
            // FloatingActionButton.
            SizedBox(height: 8),
            TextFormField(
              focusNode: myFocusNode,
              decoration: InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'Last Name',
              ),
            ),
            
            SizedBox(height: 8),
            TextFormField(
              decoration: InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'Birthdate',
                suffixIcon: Icon(Icons.calendar_today),
              ),
            ),
            
            SizedBox(height: 20),
            Container(
              padding: EdgeInsets.symmetric(vertical: 10.0),
              child: Align(
                alignment: Alignment.centerLeft,
                
                child: Text(
              'Company Information',
              style: TextStyle(fontWeight: FontWeight.bold),
            ),
              ),
            ),
            
            // The first text field is focused on as soon as the app starts.
            TextFormField(
              decoration: InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'Company Name',
              ),
            ),
            // The second text field is focused on when a user taps the
            // FloatingActionButton.
            SizedBox(height: 8),
            TextFormField(
              decoration: InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'Department',
              ),
            ),
            
            SizedBox(height: 8),
            TextFormField(
              decoration: InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'Currency',
                suffixIcon: Icon(Icons.keyboard_arrow_down),
              ),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        // When the button is pressed,
        // give focus to the text field using myFocusNode.
        onPressed: () => FocusScope.of(context).requestFocus(myFocusNode),
        tooltip: 'Focus Second Text Field',
        child: Icon(Icons.edit),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

https://dartpad.dev/47a94e96be8427ae7c8241674c991ef7