Add Firebase messaging (Android-only, foreground-only)

lib/env/dev.json

@@ -1,5 +1,5 @@
 {
   "env": "DEV",
   "production": false,
-  "apiUrl": "https://dev.localspend.co.uk/api"
-}
+  "apiUrl": "https://localhost:/api"
+}

lib/main.dart

@@ -7,9 +7,12 @@ import 'package:local_spend/pages/spash_screen.dart';
 import 'package:local_spend/pages/more_page.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:local_spend/common/apifunctions/get_graph_data.dart';
+import 'package:firebase_messaging/firebase_messaging.dart';
 
 void main() {
-  runApp(MyApp());
+  runApp(
+      MyApp()
+  );
 }
 
 void loadGraphs() {}
@@ -22,27 +25,43 @@ class GraphWithTitle {
 }
 
 class MyApp extends StatelessWidget {
+  final FirebaseMessaging _firebaseMessaging = FirebaseMessaging();
   @override
   Widget build(BuildContext context) {
     // TODO: load graphs on app login and send to graph widgets
 
-    return new MaterialApp(
+    _firebaseMessaging.configure(
+      onMessage: (Map<String, dynamic> message) async {
+        print('onMessage: $message');
+      },
+      onLaunch: (Map<String, dynamic> message) async {
+        print('onLaunch: $message');
+      },
+      onResume: (Map<String, dynamic> message) async {
+        print('onResume: $message');
+      },
+    );
+
+    // Required on iOS; non-op on Android.
+    _firebaseMessaging.requestNotificationPermissions();
+
+    return MaterialApp(
       debugShowCheckedModeBanner: false,
       localizationsDelegates: [
         GlobalMaterialLocalizations.delegate,
         GlobalWidgetsLocalizations.delegate,
       ],
-      supportedLocales: [Locale("en")],
-      title: "Local Spend Tracker",
-      theme: new ThemeData(
+      supportedLocales: [Locale('en')],
+      title: 'Local Spend Tracker',
+      theme: ThemeData(
         primarySwatch: Colors.blueGrey,
       ),
       routes: <String, WidgetBuilder>{
-        "/HomePage": (BuildContext context) => HomePage(),
-        "/LoginPage": (BuildContext context) => LoginPage(),
+        '/HomePage': (BuildContext context) => HomePage(),
+        '/LoginPage': (BuildContext context) => LoginPage(),
         '/MapPage': (BuildContext context) => MapPage(),
-        "/ReceiptPage": (BuildContext context) => ReceiptPage2(),
-        "/MorePage": (BuildContext context) => MorePage(),
+        '/ReceiptPage': (BuildContext context) => ReceiptPage2(),
+        '/MorePage': (BuildContext context) => MorePage(),
       },
       home: SplashScreen(),
     );