Improve dark theme

lib/helpers/preferences_helper.dart

@@ -71,3 +71,10 @@ class PreferencesHelper {
     return v == null ? alternative : v;
   }
 }
+
+PreferencesHelper preferences() {
+  if (PreferencesHelper._instance == null)
+    throw Exception("Try to get preference before their initialization!");
+
+  return PreferencesHelper._instance;
+}

lib/main.dart

@@ -32,7 +32,7 @@ class ComunicApplication extends StatelessWidget {
     return MaterialApp(
       debugShowCheckedModeBanner: false,
       home: ComunicApplicationHome(),
-      theme: darkMode ? ThemeData.dark() : null,
+      theme: darkMode ? ThemeData.dark() : ThemeData.light(),
     );
   }
 }

lib/ui/tiles/comment_tile.dart

@@ -4,6 +4,7 @@ import 'package:comunic/ui/widgets/account_image_widget.dart';
 import 'package:comunic/ui/widgets/network_image_widget.dart';
 import 'package:comunic/utils/date_utils.dart';
 import 'package:comunic/utils/intl_utils.dart';
+import 'package:comunic/utils/ui_utils.dart';
 import 'package:flutter/material.dart';
 
 /// Single comment tile
@@ -90,7 +91,7 @@ class CommentTile extends StatelessWidget {
           child: comment.hasContent
               ? Text(
                   comment.content,
-                  style: TextStyle(color: Colors.black),
+                  style: TextStyle(color: darkTheme() ? darkAccentColor : Colors.black),
                 )
               : null,
         ),

lib/ui/tiles/conversation_message_tile.dart

@@ -5,6 +5,7 @@ import 'package:comunic/ui/widgets/network_image_widget.dart';
 import 'package:comunic/ui/widgets/text_rich_content_widget.dart';
 import 'package:comunic/utils/date_utils.dart';
 import 'package:comunic/utils/intl_utils.dart';
+import 'package:comunic/utils/ui_utils.dart';
 import 'package:flutter/material.dart';
 
 /// Conversation message tile
@@ -201,12 +202,17 @@ class ConversationMessageTile extends StatelessWidget {
                               child: TextRichContentWidget(
                                 message.message,
                                 textAlign: TextAlign.justify,
-                                style: TextStyle(color: Colors.black),
+                                style: TextStyle(
+                                    color: darkTheme()
+                                        ? Colors.white
+                                        : Colors.black),
                               ),
                               padding:
                                   EdgeInsets.fromLTRB(15.0, 10.0, 15.0, 10.0),
                               decoration: BoxDecoration(
-                                color: Colors.black12,
+                                color: darkTheme()
+                                    ? Colors.white12
+                                    : Colors.black12,
                                 borderRadius: BorderRadius.circular(8.0),
                               ),
                             ),

lib/ui/tiles/conversation_tile.dart

@@ -3,6 +3,7 @@ import 'package:comunic/lists/users_list.dart';
 import 'package:comunic/models/conversation.dart';
 import 'package:comunic/utils/date_utils.dart';
 import 'package:comunic/utils/intl_utils.dart';
+import 'package:comunic/utils/ui_utils.dart';
 import 'package:flutter/material.dart';
 
 /// Single conversation tile
@@ -67,7 +68,9 @@ class ConversationTile extends StatelessWidget {
       // Leading icon
       leading: Icon(
         conversation.sawLastMessage ? Icons.check_circle : Icons.lens,
-        color: conversation.sawLastMessage ? null : Colors.blue,
+        color: conversation.sawLastMessage
+            ? (darkTheme() ? darkAccentColor : null)
+            : Colors.blue,
       ),
 
       // Conversation information

lib/ui/tiles/post_tile.dart

@@ -345,7 +345,7 @@ class _PostTileState extends State<PostTile> {
     comments.add(_buildCommentsForm());
 
     return Container(
-      color: Colors.grey[300],
+      color: darkTheme() ? Colors.black38 : Colors.grey[300],
       child: Padding(
         padding: const EdgeInsets.only(top: 8.0, bottom: 8.0),
         child: Column(
@@ -375,10 +375,15 @@ class _PostTileState extends State<PostTile> {
               controller: _commentController,
               onChanged: (s) => setState(() {}),
               onSubmitted: _canSubmitComment ? (s) => _submitComment() : null,
+
+              style: TextStyle(
+                color: darkTheme() ? Colors.white : null,
+              ),
+
               decoration: InputDecoration(
                 hintText: tr("New comment..."),
                 hintStyle: TextStyle(color: Colors.grey, fontSize: 12),
-                fillColor: Colors.white,
+                fillColor: darkTheme() ? Colors.black38 : Colors.white,
                 filled: true,
                 border: OutlineInputBorder(
                     borderSide: BorderSide(width: 0.5, color: Colors.grey),

lib/ui/widgets/navbar_widget.dart

@@ -1,4 +1,5 @@
 import 'package:comunic/utils/intl_utils.dart';
+import 'package:comunic/utils/ui_utils.dart';
 import 'package:flutter/material.dart';
 
 /// Navigation bar widget
@@ -18,8 +19,8 @@ enum BarCallbackActions {
   ACTION_LOGOUT
 }
 
-const _PrimaryColor = Colors.blue;
-const _SecondaryColor = Colors.white;
+Color _primaryColor() => darkTheme() ? Colors.black : Colors.blue;
+Color _secondaryColor() => darkTheme() ? darkAccentColor : Colors.white;
 
 /// Menu item information
 class _MenuItem {
@@ -93,7 +94,7 @@ class ComunicAppBar extends StatelessWidget implements PreferredSizeWidget {
   @override
   Widget build(BuildContext context) {
     return Material(
-      color: Colors.blue,
+      color: darkTheme() ? Colors.black : Colors.blue,
       child: Row(
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: List.generate(
@@ -134,7 +135,7 @@ class _MenuItemWidget extends StatelessWidget {
 
     return Expanded(
       child: Material(
-        color: isSelected ? _SecondaryColor : _PrimaryColor,
+        color: isSelected ? _secondaryColor() : _primaryColor(),
         child: !item.isMenu
             ? InkWell(
                 child: _buildIconContainer(),
@@ -151,7 +152,7 @@ class _MenuItemWidget extends StatelessWidget {
       children: <Widget>[
         IconTheme(
           data: IconThemeData(
-              color: isSelected ? _PrimaryColor : _SecondaryColor),
+              color: isSelected ? _primaryColor() : _secondaryColor()),
           child: item.icon,
         )
       ],

lib/utils/ui_utils.dart

@@ -1,4 +1,5 @@
 import 'package:cached_network_image/cached_network_image.dart';
+import 'package:comunic/helpers/preferences_helper.dart';
 import 'package:comunic/utils/intl_utils.dart';
 import 'package:flutter/material.dart';
 import 'package:html/parser.dart';
@@ -179,3 +180,9 @@ String htmlDecodeCharacters(String input) {
 
   return parse(input).documentElement.text;
 }
+
+
+const darkAccentColor = Colors.white70;
+
+/// Check out whether dark theme is enabled or not
+bool darkTheme() => preferences().getBool(PreferencesKeyList.ENABLE_DARK_THEME);