Dynamically added TextFields

main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  List<TextEditingController> _controllers;

  @override
  void initState() {
    super.initState();
    _controllers = List.generate(_counter, (index) => createController());
  }

  @override
  void dispose() {
    _controllers.forEach((c) => c.dispose());
    super.dispose();
  }

  TextEditingController createController() => TextEditingController();

  void _incrementCounter() {
    setState(() {
      _counter++;
      _controllers.add(createController());
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: ListView.builder(
        itemCount: _counter,
        itemBuilder: (context, index) {
          return TextField(
            controller: _controllers[index],
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}