added default theme

lib/main.dart

@@ -7,6 +7,8 @@ import 'pages/main_navigation_scaffold.dart';
 import 'services/flood_station_provider.dart';
 import 'package:timezone/data/latest.dart' as tz;
 
+import 'theme.dart';
+
 void main() {
   runApp(
     ChangeNotifierProvider(
@@ -24,10 +26,7 @@ class MyApp extends StatelessWidget {
     tz.initializeTimeZones();
     return MaterialApp(
       title: 'Floodwatch',
-      theme: ThemeData(
-          colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
-          useMaterial3: true,
-          fontFamily: 'UbuntuSansMono'),
+      theme: defaultTheme,
       initialRoute: MainNavigationScaffold.routeName,
       routes: {
         MainNavigationScaffold.routeName: (context) => MainNavigationScaffold(),

lib/theme.dart

@@ -0,0 +1,35 @@
+import 'package:flutter/material.dart';
+
+ThemeData get defaultTheme {
+  return ThemeData(
+    fontFamily: 'UbuntuSansMono',
+    colorScheme: ColorScheme.fromSeed(
+      seedColor: Colors.amber,
+      brightness: Brightness.light,
+    ),
+    textTheme: _defaultTextTheme,
+  );
+}
+
+ThemeData get defaultDarkTheme {
+  return ThemeData(
+    fontFamily: 'UbuntuSansMono',
+    colorScheme: ColorScheme.fromSeed(
+      seedColor: Colors.lightGreen,
+      brightness: Brightness.dark,
+    ),
+    textTheme: _defaultTextTheme,
+  );
+}
+
+TextTheme get _defaultTextTheme => TextTheme(
+      titleLarge: TextStyle(
+        fontWeight: FontWeight.w800,
+      ),
+      titleMedium: TextStyle(
+        fontWeight: FontWeight.w800,
+      ),
+      titleSmall: TextStyle(
+        fontWeight: FontWeight.w800,
+      ),
+    );

lib/widgets/reading_graph.dart

@@ -48,12 +48,14 @@ class ReadingGraph extends StatelessWidget {
         ),
         lineTouchData: LineTouchData(
           touchTooltipData: LineTouchTooltipData(
+            getTooltipColor: (touchedSpot) =>
+                Theme.of(context).colorScheme.primaryContainer,
             getTooltipItems: (touchedSpots) {
               return touchedSpots.map((touchedSpot) {
                 return LineTooltipItem(
                     '${touchedSpot.y.toString()}\n${_getLongDate(touchedSpot.x)}',
                     TextStyle(
-                        color: Theme.of(context).colorScheme.onPrimary,
+                        color: Theme.of(context).colorScheme.onPrimaryContainer,
                         fontWeight: FontWeight.bold));
               }).toList();
             },