added cargo files

PinePods-0.8.2/mobile/lib/navigation/navigation_route_observer.dart

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+// Copyright 2020 Ben Hills and the project contributors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+
+/// This class will observe the current route.
+///
+/// This gives us an easy way to tell what screen we are on from elsewhere within
+/// the application. This is useful, for example, when responding to external links
+/// and determining if we need to display the podcast details or just update the
+/// current screen.
+class NavigationRouteObserver extends NavigatorObserver {
+  final List<Route<dynamic>?> _routeStack = <Route<dynamic>?>[];
+
+  static final NavigationRouteObserver _instance = NavigationRouteObserver._internal();
+
+  NavigationRouteObserver._internal();
+
+  factory NavigationRouteObserver() {
+    return _instance;
+  }
+
+  @override
+  void didPop(Route<dynamic> route, Route<dynamic>? previousRoute) {
+    _routeStack.removeLast();
+  }
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
+    _routeStack.add(route);
+  }
+
+  @override
+  void didRemove(Route<dynamic> route, Route<dynamic>? previousRoute) {
+    _routeStack.remove(route);
+  }
+
+  @override
+  void didReplace({Route<dynamic>? newRoute, Route<dynamic>? oldRoute}) {
+    int oldRouteIndex = _routeStack.indexOf(oldRoute);
+
+    _routeStack.replaceRange(oldRouteIndex, oldRouteIndex + 1, [newRoute]);
+  }
+
+  Route<dynamic>? get top => _routeStack.last;
+}