My Goal: In the following minimal code, I have MyMainInputWidget and YearInputWidget as input capturing widgets which are required. I don't want to call any provider methods within the YearInputWidget class file because I want to keep it clean and separate the code/logic. So, as you should see, I have called MyMainInputWidget in the main.dart file, and MyMainInputWidget has nested YearInputWidget. The provider logic are required to be placed in main.dart and MyMainInputWidget as I have shown below. The aim is that on pressing the Set to this Year elevated button in main.dart, the current year should appear in the TextField. I hope I am clear with my goal. If needed please comment for more clarification.

My Problem: The provider's Consumer only updates what is within the builder, it does not trigger a rebuild down the widget tree, and so the current year is not being displayed in the TextField as evident by the debug print statements we can see in the debug console: the year is accurately passed to the YearInputWidget in its yearInputString property but as a rebuild is not triggered the TextField display value is not updated.

What I Tried: I have tried didChangeDependencies which does not seem to work in this case. I tried to call setState in the YearInputWidget based on the value of its yearInputString property being null or non-null: which failed too. I also tried reusing/reassigning the TextEditingController of associated textField but that results in exception.

Question: So, how can I fix the issue described above?

Minimal code below for the demo project:

lib/main.dart:

import 'package:flutter/material.dart';
import 'package:flutter_consumer_doesnt_rebuild_down_the_widget_tree/my_main_input_widget.dart';
import 'package:flutter_consumer_doesnt_rebuild_down_the_widget_tree/my_provider.dart';
import 'package:provider/provider.dart';

void main() {
  runApp(
    MultiProvider(
      providers: [
        ChangeNotifierProvider<MyProvider>(create: (context) => MyProvider()),
      ],
      child: const MyApp(),
    ),
  );
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: MyHomePage());
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

class _MyHomePageState extends State<MyHomePage> {
  late MyProvider myProviderObj;

  @override
  void initState() {
    super.initState();
    myProviderObj = Provider.of<MyProvider>(context, listen: false);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text("Example")),
      body: Column(
        children: [
          const Text("Hello world"),
          MyMainInputWidget(),
          ElevatedButton(
            onPressed: () {
              myProviderObj.setThisYear();
            },
            child: const Text("Set to this Year"),
          ),
        ],
      ),
    );
  }
}

lib/my_main_input_widget.dart:

import 'package:flutter/material.dart';
import 'package:flutter_consumer_doesnt_rebuild_down_the_widget_tree/my_provider.dart';
import 'package:flutter_consumer_doesnt_rebuild_down_the_widget_tree/year_input_widget.dart';
import 'package:provider/provider.dart';

class MyMainInputWidget extends StatefulWidget {
  const MyMainInputWidget({super.key});

  @override
  State<MyMainInputWidget> createState() => _MyMainInputWidgetState();
}

class _MyMainInputWidgetState extends State<MyMainInputWidget> {
  String? _yearInputString;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Consumer<MyProvider>(
          builder: (context, myProvider, child) {
            if (myProvider.toSetToThisYear) {
              int thisYear = DateTime.now().year;
              _yearInputString = thisYear.toString();
            } else {
              _yearInputString = null;
            }
            print(
              "#### MyMainInputWidget :: _yearInputString=${_yearInputString}",
            );
            return YearInputWidget(
              yearInputString: _yearInputString,
              child: SizedBox(),
            );
          },
        ),
      ],
    );
  }
}

lib/year_input_widget.dart:

import 'package:flutter/material.dart';

class YearInputWidget extends StatefulWidget {
  final String? yearInputString;
  final Function(String year)? getInputYearFieldValue;
  final Widget child;
  const YearInputWidget({
    super.key,
    this.yearInputString,
    this.getInputYearFieldValue,
    required this.child,
  });

  @override
  State<YearInputWidget> createState() => _YearInputWidgetState();
}

class _YearInputWidgetState extends State<YearInputWidget> {
  late final TextEditingController controllerYear;
  late final TextEditingController controllerMonth;
  late final TextEditingController controllerDay;

  void _myBuildContent() {
    print("#### _myBuildContent() method executed!");
    if (widget.yearInputString != null) {
      // controllerYear.text = widget.yearInputString!;
      controllerYear.dispose();
      controllerYear = TextEditingController(text: widget.yearInputString);
    }
  }

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

    /*
    controllerYear = widget.yearInputString == null
        ? TextEditingController()
        : TextEditingController(text: widget.yearInputString);
    */
    controllerYear = TextEditingController();
    controllerMonth = TextEditingController();
    controllerDay = TextEditingController();

    _myBuildContent();
  }

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

    _myBuildContent();
  }

  @override
  void dispose() {
    controllerYear.dispose();
    controllerMonth.dispose();
    controllerDay.dispose();

    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    print(
      "#### DateInputWidget:: widget.yearInputString=${widget.yearInputString}",
    );
    print("#### DateInputWidget:: controllerYear.text=${controllerYear.text}");
    /*
    if (widget.yearInputString != null) {
      print("Since, widget.yearInputString is not null, calling setState ...");
      setState(() {});
    }
    */
    _myBuildContent();
    return Container(
      padding: const EdgeInsets.all(15.0),
      width: double.infinity,
      // height: 250.0,
      decoration: BoxDecoration(
        // DARK THEME INFLEXIBLE CODE:
        // color: const Color(0xfff7faff),
        color: Colors.amberAccent,
        borderRadius: BorderRadius.circular(8.0),
        border: Border.all(
          width: 1.0,
          // DARK THEME INFLEXIBLE CODE:
          // color: const Color(0xffeceef1),
          color: Colors.amberAccent.shade700,
        ),
      ),
      child: Row(
        children: [
          // NEW START:
          Expanded(
            flex: 1,
            // child: Center(child: const Text("YEAR")),
            child: Center(
              child: Text(
                "YEAR",
                // DARK THEME INFLEXIBLE CODE:
                style: Theme.of(context).textTheme.labelSmall!.copyWith(
                  fontSize: 10,
                  color: Colors.blue.withAlpha(128),
                ),
              ),
            ),
          ),
          Expanded(
            flex: 1,
            child: TextField(
              controller: controllerYear,
              textAlign: TextAlign.center,
              keyboardType: TextInputType.number,
              decoration: const InputDecoration(hintText: "yyyy"),
              onChanged: (value) {
                if (widget.getInputYearFieldValue != null) {
                  widget.getInputYearFieldValue!(value);
                }
              },
            ),
          ),

          // NEW END.
        ],
      ),
    );
  }
}

lib/my_provider.dart:

import 'package:flutter/material.dart';

class MyProvider with ChangeNotifier {
  bool _setToThisYear = false;
  bool get toSetToThisYear => _setToThisYear;
  void setThisYear() {
    _setToThisYear = true;
    notifyListeners();
  }
}