birzha_mobile/lib/components/tabview.dart

import 'package:birzha/constants.dart';
import 'package:birzha/core/adaptix/adaptix.dart';
import 'package:flutter/material.dart';
import 'package:google_nav_bar/google_nav_bar.dart';
import 'package:provider/provider.dart';

class TabView extends StatefulWidget {
  TabView({required this.items});

  final List<TabConfigs> items;

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

class _TabViewState extends State<TabView> {
  late final List<GlobalKey<NavigatorState>> navigatorKeys;
  late final PageController controller;

  Future<bool> pop(BuildContext cntxt) async {
    final tabnavigator = Provider.of<Tabnavigator>(cntxt, listen: false);
    bool canPop = await navigatorKeys[tabnavigator.index].currentState?.maybePop() ?? true;
    if (canPop) {
      return false;
    } else if (tabnavigator.stack.length > 1) {
      setState(() {
        tabnavigator._removefromStack();
        changePage(tabnavigator.stack.last);
      });
      return false;
    } else if (tabnavigator.stack.length == 1 && tabnavigator.index != 0) {
      setState(() {
        tabnavigator._removefromStack();
        changePage(0);
      });
      return false;
    }
    return true;
  }

  void changePage(int index) {
    controller.jumpToPage(index);
  }

  void onPageChange(BuildContext cntxt, int index) {
    Provider.of<Tabnavigator>(cntxt, listen: false)._setIndex(index);
  }

  @override
  void initState() {
    navigatorKeys = [for (var item in widget.items) LabeledGlobalKey<NavigatorState>(item.initialRouteName)];
    controller = PageController();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (_) => Tabnavigator(
          currentRouteName: (index) {
            return widget.items[index].initialRouteName;
          },
          changePage: changePage,
          pop: pop,
          rootNavContext: context),
      builder: (context, _) => WillPopScope(
        onWillPop: () => pop(context),
        child: Consumer<Tabnavigator>(
          builder: (context, tabnav, __) {
            return Scaffold(
              bottomNavigationBar: Container(
                color: Theme.of(context).bottomNavigationBarTheme.backgroundColor ?? Colors.white,
                padding: EdgeInsets.symmetric(horizontal: AppConstants.horizontalPadding(context) / 2).copyWith(bottom: Adaptix.systemPadding.bottom),
                child: GNav(
                  tabBorderRadius: 20.adaptedPx(),
                  curve: Curves.easeInCubic,
                  duration: Duration(milliseconds: 280),
                  selectedIndex: tabnav.index,
                  backgroundColor: Colors.transparent,
                  gap: 10.adaptedPx(),
                  color: Theme.of(context).accentColor,
                  activeColor: Theme.of(context).accentColor,
                  iconSize: 18.7.adaptedPx(),
                  textStyle: Theme.of(context).textTheme.headline2?.copyWith(
                      color: Theme.of(context).accentColor,
                      fontSize: AppConstants.h2FontSize * 0.93,
                      // body text uly headlinedan kichi
                      fontWeight: FontWeight.w500,
                      height: 1.3),
                  tabBackgroundColor: Theme.of(context).bottomNavigationBarTheme.selectedItemColor ?? Colors.grey.shade300,
                  tabMargin: EdgeInsets.symmetric(vertical: 8.adaptedPx()),
                  padding: EdgeInsets.symmetric(horizontal: 10.adaptedPx(), vertical: 13.2.adaptedPx()),
                  onTabChange: (index) {
                    onPageChange(context, index);
                    changePage(index);
                  },
                  tabs: <GButton>[
                    for (var item in widget.items)

                      /// those items are integrated from each single tabconfig from widget.items
                      GButton(
                        icon: item.iconData,
                        text: item.routeLabel,
                        active: true,
                      ),
                  ],
                ),
              ),
              body: Column(
                children: [
                  //will create as much Navigators as the length of widget.items.length
                  Expanded(
                    child: PageView.builder(
                      itemCount: widget.items.length,
                      onPageChanged: (newPageIndex) {
                        onPageChange(context, newPageIndex);
                      },
                      controller: controller,
                      itemBuilder: (_, index) => Navigator(
                        initialRoute: widget.items[index].initialRouteName,
                        key: navigatorKeys[index],
                        onGenerateInitialRoutes: (_, __) {
                          return [
                            //each first screen of each item in widget.items
                            MaterialPageRoute(builder: widget.items[index].firstScreen),
                          ];
                        },
                      ),
                    ),
                  ),
                ],
              ),
            );
          },
        ),
      ),
    );
  }
}

///describes each gbutton, each tab and e.t.c -> creaet list of items in [TabView] constructor
class TabConfigs {
  final int index;
  final Widget Function(BuildContext) firstScreen;
  final String routeLabel;
  final IconData iconData;
  final String initialRouteName;

  TabConfigs({
    required this.index,
    required this.firstScreen,
    required this.routeLabel,
    required this.iconData,
    required this.initialRouteName,
  });
}

class Tabnavigator extends ChangeNotifier {
  int index = 0;
  Set<int> stack = <int>{0};
  late final Future<bool> Function(BuildContext cntxt) pop;
  late final String Function(int) currentRouteName;
  late final void Function(int) _changePage;
  late final BuildContext rootNavContext;

  Tabnavigator({required void Function(int) changePage, required this.currentRouteName, required this.pop, required this.rootNavContext}) {
    _changePage = changePage;
  }

  Map<int, dynamic> _routeSettingsTable = {};

  void changePage(int page, [dynamic payload]) {
    _routeSettingsTable[page] = payload;
    _changePage(page);
    notifyListeners();
  }

  dynamic getPayloadOf(int page) {
    return _routeSettingsTable[page];
  }

  void _setIndex(int i) {
    index = i;
    stack.remove(i);
    stack.add(i);
    notifyListeners();
  }

  void _removefromStack() {
    _routeSettingsTable.remove(stack.last);
    var listFromStack = [...stack]..removeLast();
    stack = {...listFromStack};
    index = stack.last;
    notifyListeners();
  }

  static Tabnavigator? maybeOf(BuildContext context) {
    try {
      return Provider.of<Tabnavigator>(context, listen: false);
    } catch (e) {}
  }

  static backDispatcher(BuildContext context) {
    if (Tabnavigator.maybeOf(context) == null)
      Navigator.of(context).pop();
    else
      Tabnavigator.maybeOf(context)!.pop(context);
  }

  static String currentRoute(BuildContext context) {
    var nav = Tabnavigator.maybeOf(context);
    if (nav == null) {
      return '/root';
    } else {
      return nav.currentRouteName(nav.index);
    }
  }
}