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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Retrieve Text Input',
      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> {
  // Create a text controller and use it to retrieve the current value
  // of the TextField.
  final myController = TextEditingController(text: 'I love flutter!');
  final newController = TextEditingController(text: 'I am a new controller.');
  TextEditingController _controller;

  @override
  void initState() {
    super.initState();
    _controller = myController;

    _controller.addListener(_printLatestValue);
  }

  @override
  void dispose() {
    // Clean up the controller when the widget is removed from the widget tree.
    // This also removes the _printLatestValue listener.
    myController.dispose();
    newController.dispose();
    super.dispose();
  }

  _printLatestValue() {
    print("Second text field: ${myController.text}");
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Retrieve Text Input'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          children: <Widget>[
//            TextField(
//              onChanged: (text) {
//                print("First text field: $text");
//              },
//            ),
            TextField(
              controller: _controller,
              keyboardType: TextInputType.multiline,
              maxLines: 7,
//              inputFormatters: [LengthLimitingTextInputFormatter(3)],
            ),
            MaterialButton(
                child: Text("set to '123'"),
                onPressed: () {
                  setState(() {
                    _controller.value = TextEditingValue(
                        text: '123',
                        composing:TextRange(start: -1, end: -1),
                        selection: TextSelection(
                            baseOffset: 3,
                            extentOffset: 3,
                            affinity: TextAffinity.downstream,
                            isDirectional: false));
                  });
                }),
            MaterialButton(
                child: Text("set to '12'"),
                onPressed: () {
                  setState(() {
                    _controller.text = '12';
                  });
                }),
            MaterialButton(
                child: Text('change controller'),
                onPressed: () {
                  setState(() {
                    _controller = newController;
                  });
                }),
          ],
        ),
      ),
    );
  }
}