Add a basic dark theme

It's not that pretty, but this adds the scaffolding.

lib/app.dart

@@ -12,6 +12,7 @@ import 'package:journal/settings.dart';
 import 'package:journal/state_container.dart';
 import 'package:journal/utils.dart';
 import 'package:shared_preferences/shared_preferences.dart';
+import 'package:dynamic_theme/dynamic_theme.dart';
 
 import 'screens/githostsetup_screens.dart';
 import 'screens/onboarding_screens.dart';
@@ -111,6 +112,32 @@ class JournalApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    return DynamicTheme(
+      defaultBrightness: Brightness.light,
+      data: (brightness) {
+        if (brightness == Brightness.light) {
+          return ThemeData(
+            brightness: Brightness.light,
+            primaryColor: Color(0xFF66bb6a),
+            primaryColorLight: Color(0xFF98ee99),
+            primaryColorDark: Color(0xFF338a3e),
+            accentColor: Color(0xff6d4c41),
+          );
+        } else {
+          return ThemeData(
+            brightness: Brightness.dark,
+            primaryColor: Color(0xFF66bb6a),
+            primaryColorLight: Color(0xFF98ee99),
+            primaryColorDark: Color(0xFF338a3e),
+            accentColor: Color(0xff6d4c41),
+          );
+        }
+      },
+      themedWidgetBuilder: buildApp,
+    );
+  }
+
+  MaterialApp buildApp(BuildContext context, ThemeData themeData) {
     var stateContainer = StateContainer.of(context);
 
     var initialRoute = '/';
@@ -121,13 +148,7 @@ class JournalApp extends StatelessWidget {
     return MaterialApp(
       key: ValueKey("App"),
       title: 'GitJournal',
-      theme: ThemeData(
-        brightness: Brightness.light,
-        primaryColor: Color(0xFF66bb6a),
-        primaryColorLight: Color(0xFF98ee99),
-        primaryColorDark: Color(0xFF338a3e),
-        accentColor: Color(0xff6d4c41),
-      ),
+      theme: themeData,
       navigatorObservers: <NavigatorObserver>[JournalApp.observer],
       initialRoute: initialRoute,
       routes: {

lib/screens/settings_screen.dart

@@ -3,6 +3,7 @@ import 'package:journal/settings.dart';
 import 'package:journal/utils.dart';
 
 import 'package:preferences/preferences.dart';
+import 'package:dynamic_theme/dynamic_theme.dart';
 
 class SettingsScreen extends StatelessWidget {
   @override
@@ -143,6 +144,24 @@ class SettingsListState extends State<SettingsList> {
 
     return PreferencePage([
       PreferenceTitle('Display Settings'),
+      DropdownPreference(
+        'Theme',
+        'theme',
+        defaultVal: "Light",
+        values: ["Light", "Dark"],
+        onChange: (newVal) {
+          var dynamicTheme = DynamicTheme.of(context);
+          switch (newVal) {
+            case "Dark":
+              dynamicTheme.setBrightness(Brightness.dark);
+              break;
+            case "Light":
+            case "default":
+              dynamicTheme.setBrightness(Brightness.light);
+              break;
+          }
+        },
+      ),
       DropdownPreference(
         'Font Size',
         'font_size',

pubspec.lock

@@ -99,6 +99,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "0.0.5+1"
+  dynamic_theme:
+    dependency: "direct main"
+    description:
+      name: dynamic_theme
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.1"
   file:
     dependency: transitive
     description:

pubspec.yaml

@@ -26,6 +26,7 @@ dependencies:
   auto_size_text: ^2.0.1
   fimber: ^0.3.0
   preferences: ^4.0.0
+  dynamic_theme: ^1.0.0
 
 dev_dependencies:
   flutter_launcher_icons: "^0.7.2"