How can I pass flutter textediting controller value from one stateless widget to another stateless widget

Question

Here Is the main.dart file:

import 'package:flutter/material.dart';
import 'package:untitled/button.dart';
import 'package:untitled/form.dart';

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

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

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[MyForm(), MyButton()],
        ),
      ),
    );
  }
}

Here is form.dart file:

import 'package:flutter/material.dart';

class MyForm extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    TextEditingController x = TextEditingController();
    return Container(
      child: Center(
        child: TextField(
          controller: x,
          decoration: InputDecoration(labelText: "Name"),
        ),
      ),
    );
  }
}

Here is button.dart file:

import 'package:flutter/material.dart';

class MyButton extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Center(
        child: ElevatedButton(
          onPressed: () {
            //if I press this button the textediting field will show 10
          },
          child: Text("Pass 10"),
        ),
      ),
    );
  }
}

1. How can I show data in text editingfield if I press the button in button.dart?
   
2. What is the optimal way to do these things?
   
3. Should I use statefulwidgets in statelesswidget or statelesswidgets in statefulwidgets?

My thought is to use redux or provider to pass this kind of things. Although I don't know this simple thing need state management system or not.

Answer 1

You need to lift the state up (create your controller in the main and pass it to the children)

// main.dart
class _MyHomePageState extends State<MyHomePage> {
  TextEditingController x = TextEditingController();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[MyForm(x), MyButton(x)],
        ),
      ),
    );
  }
}

class MyForm extends StatelessWidget {
  MyForm(this.x);
  final TextEditingController x;
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Center(
        child: TextField(
          controller: x,
          decoration: InputDecoration(labelText: "Name"),
        ),
      ),
    );
  }
}

class MyButton extends StatelessWidget {
  MyButton(this.x);
  final TextEditingController x;
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Center(
        child: ElevatedButton(
          onPressed: () {
            x...
            //if I press this button the textediting field will show 10
          },
          child: Text("Pass 10"),
        ),
      ),
    );
  }
}