fix navbar matching when using global back button

lib/main.dart

@@ -1,7 +1,9 @@
 import 'package:flutter/material.dart';
 import 'package:dynamic_color/dynamic_color.dart';
 import 'package:mileograph_flutter/components/pages/calculator.dart';
+import 'package:mileograph_flutter/components/pages/newEntry.dart';
 import 'package:mileograph_flutter/components/pages/traction.dart';
+import 'package:mileograph_flutter/components/pages/trips.dart';
 import 'package:provider/provider.dart';
 
 import 'package:mileograph_flutter/components/pages/legs.dart';
@@ -85,8 +87,14 @@ class MyApp extends StatelessWidget {
           routes: [
             GoRoute(path: '/', builder: (_, __) => const Dashboard()),
             GoRoute(path: '/calculator', builder: (_, __) => CalculatorPage()),
+            GoRoute(
+              path: '/calculator/details',
+              builder: (_, __) => CalculatorPage(),
+            ),
             GoRoute(path: '/legs', builder: (_, __) => LegsPage()),
             GoRoute(path: '/traction', builder: (_, __) => TractionPage()),
+            GoRoute(path: '/trips', builder: (_, __) => TripsPage()),
+            GoRoute(path: '/add', builder: (_, __) => NewEntryPage()),
           ],
         ),
         GoRoute(path: '/login', builder: (_, __) => const LoginScreen()),
@@ -146,15 +154,29 @@ class MyHomePage extends StatefulWidget {
 }
 
 class _MyHomePageState extends State<MyHomePage> {
-  int pageIndex = 0;
   final List<String> contentPages = [
     "/",
     "/calculator",
     "/legs",
     "/traction",
-    "/",
+    "/trips",
   ];
 
+  int _getIndexFromLocation(String location) {
+    int newIndex = contentPages.indexWhere((path) => location == path);
+    if (newIndex < 0) {
+      return 0;
+    }
+    return newIndex;
+  }
+
+  void _onItemTapped(int index, int currentIndex) {
+    if (index < 0 || index >= contentPages.length || index == currentIndex)
+      return;
+    context.push(contentPages[index]);
+    _getIndexFromLocation(contentPages[index]);
+  }
+
   bool loggedIn = false;
   bool _fetched = false;
 
@@ -184,7 +206,8 @@ class _MyHomePageState extends State<MyHomePage> {
   @override
   Widget build(BuildContext context) {
     Widget currentPage;
-
+    final location = GoRouterState.of(context).uri.toString();
+    final pageIndex = _getIndexFromLocation(location);
     final data = context.watch<DataService>();
     final auth = context.read<AuthService>();
 
@@ -232,10 +255,7 @@ class _MyHomePageState extends State<MyHomePage> {
       bottomNavigationBar: NavigationBar(
         selectedIndex: pageIndex,
         onDestinationSelected: (int index) {
-          setState(() {
-            pageIndex = index;
-            context.push(contentPages[index]);
-          });
+          _onItemTapped(index, pageIndex);
         },
         destinations: [
           NavigationDestination(icon: Icon(Icons.home), label: "Home"),
@@ -247,7 +267,7 @@ class _MyHomePageState extends State<MyHomePage> {
       ),
       body: currentPage,
       floatingActionButton: FloatingActionButton(
-        onPressed: null,
+        onPressed: () => {context.push("/add")},
         tooltip: 'New Entry',
         child: const Icon(Icons.add),
       ), // This trailing comma makes auto-formatting nicer for build methods.