Add automatically determine theme feature

lib/bloc/theme/theme_bloc.dart

@@ -1,9 +1,9 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
-import 'package:get_it/get_it.dart';
-import 'package:shared_preferences/shared_preferences.dart';
 
 import '../../models/themes/theme.dart';
+import '../../settings.dart';
 
 export 'package:flutter_bloc/flutter_bloc.dart';
 export 'package:jisho_study_tool/models/themes/theme.dart';
@@ -19,12 +19,12 @@ class ThemeBloc extends Bloc<ThemeEvent, ThemeState> {
       ),
     );
 
+    final bool autoThemeIsDark =
+        SchedulerBinding.instance!.window.platformBrightness == Brightness.dark;
+
     add(
       SetTheme(
-        themeIsDark: GetIt.instance
-                .get<SharedPreferences>()
-                .getBool('darkThemeEnabled') ??
-            false,
+        themeIsDark: autoThemeEnabled ? autoThemeIsDark : darkThemeEnabled,
       ),
     );
   }

lib/main.dart

@@ -10,6 +10,7 @@ import 'package:shared_preferences/shared_preferences.dart';
 
 import 'bloc/theme/theme_bloc.dart';
 import 'routing/router.dart';
+import 'settings.dart';
 
 Future<void> setupDatabase() async {
   final Directory appDocDir = await getApplicationDocumentsDirectory();
@@ -35,14 +36,43 @@ Future<void> main() async {
   runApp(const MyApp());
 }
 
-class MyApp extends StatelessWidget {
+class MyApp extends StatefulWidget {
   const MyApp({Key? key}) : super(key: key);
 
+  @override
+  _MyAppState createState() => _MyAppState();
+}
+
+class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
+  final ThemeBloc themeBloc = ThemeBloc();
+
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance?.addObserver(this);
+  }
+
+  @override
+  void dispose() {
+    WidgetsBinding.instance?.removeObserver(this);
+    super.dispose();
+  }
+
+  @override
+  void didChangePlatformBrightness() {
+    if (autoThemeEnabled) {
+      final themeIsDark =
+          WidgetsBinding.instance?.window.platformBrightness == Brightness.dark;
+      themeBloc.add(SetTheme(themeIsDark: themeIsDark));
+    }
+    super.didChangePlatformBrightness();
+  }
+
   @override
   Widget build(BuildContext context) {
     return MultiBlocProvider(
       providers: [
-        BlocProvider(create: (context) => ThemeBloc()),
+        BlocProvider(create: (context) => themeBloc),
       ],
       child: BlocBuilder<ThemeBloc, ThemeState>(
         builder: (context, themeState) => MaterialApp(

lib/screens/settings.dart

@@ -24,6 +24,18 @@ class _SettingsViewState extends State<SettingsView> {
     }
   }
 
+  // ignore: avoid_positional_boolean_parameters
+  void toggleAutoTheme(bool b) {
+    final bool newThemeIsDark = b
+        ? WidgetsBinding.instance!.window.platformBrightness == Brightness.dark
+        : darkThemeEnabled;
+
+    BlocProvider.of<ThemeBloc>(context)
+        .add(SetTheme(themeIsDark: newThemeIsDark));
+
+    setState(() => autoThemeEnabled = b);
+  }
+
   @override
   Widget build(BuildContext context) {
     final TextStyle _titleTextStyle = TextStyle(
@@ -56,11 +68,8 @@ class _SettingsViewState extends State<SettingsView> {
           tiles: <SettingsTile>[
             SettingsTile.switchTile(
               title: 'Automatically determine theme',
-              onToggle: (b) {
-                setState(() => autoThemeEnabled = b);
-              },
+              onToggle: toggleAutoTheme,
               switchValue: autoThemeEnabled,
-              enabled: false,
               switchActiveColor: AppTheme.jishoGreen.background,
             ),
             SettingsTile.switchTile(