issue_114320

main.dart

import 'dart:async';

import 'package:flutter/material.dart';

/// THIS IS TO INJECT SOMETHING THAT NEEDS TO BE INITIALIZED IN THE CONTEXT
/// [[start]]
typedef Initialize<T> = T Function();
typedef Dispose<T> = void Function(T);

class _MyInheritedWidget<T> extends InheritedWidget {
  const _MyInheritedWidget({
    super.key,
    required this.data,
    required super.child,
  });

  final T data;

  @override
  bool updateShouldNotify(_MyInheritedWidget<T> oldWidget) =>
      data != oldWidget.data;
}

extension InheritedWidgetOfContextX on BuildContext {
  T getInherited<T>() {
    final result = dependOnInheritedWidgetOfExactType<_MyInheritedWidget<T>>();
    if (result == null) {
      throw Exception('No InheritedWidget<$T> found in BuildContext');
    }
    return result.data;
  }
}

class MyInheritedWidget<T> extends StatefulWidget {
  final Widget child;
  final Initialize<T> initialize;
  final Dispose<T> dispose;
  const MyInheritedWidget({
    super.key,
    required this.child,
    required this.initialize,
    required this.dispose,
  });

  @override
  State<MyInheritedWidget<T>> createState() => _MyInheritedWidgetState<T>();
}

class _MyInheritedWidgetState<T> extends State<MyInheritedWidget<T>> {
  late final T _data;

  @override
  void initState() {
    _data = widget.initialize();
    super.initState();
  }

  @override
  void dispose() {
    widget.dispose(_data);
    super.dispose();
  }

  @override
  Widget build(context) => _MyInheritedWidget<T>(
        data: _data,
        child: widget.child,
      );
}

/// [[end]]

void main() => runApp(const MaterialApp(home: MyApp()));

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

  @override
  Widget build(context) => MyInheritedWidget<StreamController<List<String>>>(
        initialize: () => StreamController.broadcast(),
        dispose: (controller) => controller.close(),
        child: MyTabPage(
          tabs: [
            TabWidgetUnion(
              tab: const Tab(text: 'first'),
              builder: (context) => const MyListView(),
            ),
            TabWidgetUnion(
              tab: const Tab(text: 'second'),
              builder: (context) => const Center(child: Text('SECOND TAB')),
            ),
          ],
          fab: const MyFab(),
        ),
      );
}

/// THIS HANDLES THE DATA FROM THE STREAM
/// AND USES [AutomaticKeepAliveClientMixin]
class MyListView extends StatefulWidget {
  const MyListView({super.key});

  @override
  State<MyListView> createState() => _MyListViewState();
}

class _MyListViewState extends State<MyListView>
    with AutomaticKeepAliveClientMixin {
  @override
  final wantKeepAlive = true;

  @override
  Widget build(context) {
    super.build(context);
    return StreamBuilder<List<String>>(
      stream: context.getInherited<StreamController<List<String>>>().stream,
      builder: (context, snapshot) =>
          snapshot.connectionState == ConnectionState.waiting
              ? const Center(child: CircularProgressIndicator())
              : !snapshot.hasData
                  ? const Center(child: Text('There is no data'))
                  : ListView.builder(
                      itemCount: snapshot.data!.length,
                      itemBuilder: (context, index) => Text(
                        snapshot.data![index],
                      ),
                    ),
    );
  }
}

/// THIS IS HANDLES THE TABS ( and the fab that for whatever reason
/// is accessible also in the wrong tab
/// [[start]]
@immutable
class TabWidgetUnion {
  final Tab tab;
  final WidgetBuilder builder;
  const TabWidgetUnion({required this.builder, required this.tab});
}

class MyTabPage extends StatefulWidget {
  final List<TabWidgetUnion> tabs;
  final Widget? fab;
  const MyTabPage({
    super.key,
    this.tabs = const [],
    this.fab,
  });

  @override
  State<MyTabPage> createState() => _MyTabPageState();
}

class _MyTabPageState extends State<MyTabPage> {
  @override
  Widget build(context) => DefaultTabController(
        length: widget.tabs.length,
        child: Scaffold(
          appBar: AppBar(
            bottom: PreferredSize(
              preferredSize: const Size.fromHeight(0),
              child: SizedBox(
                height: 30,
                width: double.infinity,
                child: TabBar(
                  tabs: [for (final union in widget.tabs) union.tab],
                ),
              ),
            ),
          ),
          body: TabBarView(
            children: [for (final union in widget.tabs) union.builder(context)],
          ),
          floatingActionButton: widget.fab,
        ),
      );
}

/// [[end]]

/// THIS APPENDS AND SINK A NEW STRING TO THE LIST
/// [[start]]
class MyFab extends StatelessWidget {
  const MyFab({super.key});

  @override
  Widget build(context) {
    final controller = context.getInherited<StreamController<List<String>>>();
    return StreamBuilder(
      stream: controller.stream,
      builder: (context, snapshot) => FloatingActionButton(
        onPressed: () {
          final lenght = snapshot.hasData ? snapshot.data!.length : 0;
          controller.sink.add([...?snapshot.data, 'data $lenght']);
        },
      ),
    );
  }
}
/// [[end]]