Постоянная ошибка панели навигации во Flutter ⇐ Android

[Anonymous]

Я новичок в Flutter и хотел добавить постоянную панель навигации, которая будет содержать 4 значка, ведущих на 3 разные страницы, где значок-1 является главным экраном по умолчанию. Код приложен ниже.
Я использую версию постоянной нижней навигационной панели 4.0.2
Главный экран
Главный экран
сильный>
import 'package:flutter/material.dart';
import 'package:myspace/widgets/right_drawer.dart';
import 'package:myspace/widgets/bottom_navigation_bar.dart';
import 'package:persistent_bottom_nav_bar/persistent-tab-view.dart';

class HomeScreen extends StatefulWidget {
const HomeScreen({Key? key}) : super(key: key);

@override
State createState() => _HomeScreenState();
}

class _HomeScreenState extends State {

@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.transparent,
elevation: 0.0,
title: Text(
'mySpace',
style: TextStyle(
fontSize: 24.0,
fontWeight: FontWeight.bold,
color: Colors.blue.shade900
),
),
actions: [
Builder(
builder: (context) => IconButton(
onPressed: () => Scaffold.of(context).openEndDrawer(),
icon: Icon(Icons.account_circle, color: Colors.blue.shade900, size: 30.0,)
),
),
],
),
endDrawer: const RightDrawerWidget(),
bottomNavigationBar: BottomListWidget(),
);
}
}

и файл виджета для Нижней панели навигации:
import 'package:flutter/material.dart';
import 'package:myspace/Screens/homescreen.dart';
import 'package:myspace/Screens/chat_system.dart';
import 'package:myspace/Screens/help_and_support.dart';
import 'package:myspace/Screens/news.dart';
import 'package:persistent_bottom_nav_bar/persistent-tab-view.dart';

class BottomListWidget extends StatefulWidget {
const BottomListWidget({Key? key}) : super(key: key);

@override
State createState() => _BottomListWidgetState();
}

class _BottomListWidgetState extends State {

PersistentTabController _controller = PersistentTabController(initialIndex: 0);

@override
Widget build(BuildContext context) {
return PersistentTabView(
context,
controller: _controller,
screens: _buildScreens(),
items: _navBarItems(),
confineInSafeArea: true,
itemAnimationProperties: const ItemAnimationProperties(
duration: Duration(milliseconds: 200),
curve: Curves.ease,
),
screenTransitionAnimation: const ScreenTransitionAnimation(
duration: Duration(milliseconds: 200),
curve: Curves.ease,
animateTabTransition: true
),
navBarStyle: NavBarStyle.style10,
);
}
}

List
_navBarItems() {
return [
PersistentBottomNavBarItem(
icon: const Icon(Icons.home),
title: ('Home'),
activeColorPrimary: Colors.blue.shade800,
inactiveColorPrimary: Colors.grey,
),
PersistentBottomNavBarItem(
icon: const Icon(Icons.newspaper_sharp),
title: ('Happenings'),
activeColorPrimary: Colors.blue.shade800,
inactiveColorPrimary: Colors.grey,
),
PersistentBottomNavBarItem(
icon: const Icon(Icons.support_agent_rounded),
title: ('Help'),
activeColorPrimary: Colors.blue.shade800,
inactiveColorPrimary: Colors.grey,
),
PersistentBottomNavBarItem(
icon: const Icon(Icons.message),
title: ('Chats'),
activeColorPrimary: Colors.blue.shade800,
inactiveColorPrimary: Colors.grey,
),
];
}

List _buildScreens() {
return [
const HomeScreen(),
const RecentNewsScreen(),
const HelpAndSupport(),
const ChatSystem()
];
}

После создания этого приложения я получаю сообщение об ошибке:
Launching lib\main.dart on EB2101 in debug mode...
Running Gradle task 'assembleDebug'...
/E:/flutter/.pub-cache/hosted/pub.dartlang.org/persistent_bottom_nav_bar-4.0.2/lib/persistent-tab-view.widget.dart:368:22: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
- 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/E:/flutter/packages/flutter/lib/src/widgets/binding.dart').
WidgetsBinding.instance!.addPostFrameCallback((_) {
^
/E:/flutter/.pub-cache/hosted/pub.dartlang.org/persistent_bottom_nav_bar-4.0.2/lib/animations/animations.dart:55:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
- 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/E:/flutter/packages/flutter/lib/src/widgets/binding.dart').
WidgetsBinding.instance!.addPostFrameCallback((_) {
^
/E:/flutter/.pub-cache/hosted/pub.dartlang.org/persistent_bottom_nav_bar-4.0.2/lib/nav-bar-styles/style-6-bottom-nav-bar.widget.dart:44:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
- 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/E:/flutter/packages/flutter/lib/src/widgets/binding.dart').
WidgetsBinding.instance!.addPostFrameCallback((_) {
^
/E:/flutter/.pub-cache/hosted/pub.dartlang.org/persistent_bottom_nav_bar-4.0.2/lib/nav-bar-styles/style-8-bottom-nav-bar.widget.dart:44:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
- 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/E:/flutter/packages/flutter/lib/src/widgets/binding.dart').
WidgetsBinding.instance!.addPostFrameCallback((_) {
^
/E:/flutter/.pub-cache/hosted/pub.dartlang.org/persistent_bottom_nav_bar-4.0.2/lib/nav-bar-styles/style-11-bottom-nav-bar.widget.dart:46:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
- 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/E:/flutter/packages/flutter/lib/src/widgets/binding.dart').
WidgetsBinding.instance!.addPostFrameCallback((_) {
^
/E:/flutter/.pub-cache/hosted/pub.dartlang.org/persistent_bottom_nav_bar-4.0.2/lib/nav-bar-styles/style-12-bottom-nav-bar.widget.dart:46:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
- 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/E:/flutter/packages/flutter/lib/src/widgets/binding.dart').
WidgetsBinding.instance!.addPostFrameCallback((_) {
^
/E:/flutter/.pub-cache/hosted/pub.dartlang.org/persistent_bottom_nav_bar-4.0.2/lib/nav-bar-styles/style-13-bottom-nav-bar.widget.dart:46:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
- 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/E:/flutter/packages/flutter/lib/src/widgets/binding.dart').
WidgetsBinding.instance!.addPostFrameCallback((_) {
^
/E:/flutter/.pub-cache/hosted/pub.dartlang.org/persistent_bottom_nav_bar-4.0.2/lib/nav-bar-styles/style-14-bottom-nav-bar.widget.dart:46:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
- 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/E:/flutter/packages/flutter/lib/src/widgets/binding.dart').
WidgetsBinding.instance!.addPostFrameCallback((_) {
^


Подробнее здесь: https://stackoverflow.com/questions/734 ... in-flutter