#57 AMOLED theme

lib/view/page/setting.dart

@@ -365,15 +365,17 @@ class _SettingPageState extends State<SettingPage> {
   }
 
   Widget _buildThemeMode() {
-    final items = ThemeMode.values.map(
-      (e) {
-        final str = _buildThemeModeStr(e.index);
-        return PopupMenuItem(
-          value: e.index,
-          child: Text(str),
-        );
-      },
-    ).toList();
+    final items = ThemeMode.values
+        .map(
+          (e) => PopupMenuItem(
+            value: e.index,
+            child: Text(_buildThemeModeStr(e.index)),
+          ),
+        )
+        .toList();
+    // Issue #57
+    final len = ThemeMode.values.length;
+    items.add(PopupMenuItem(value: len, child: Text(_buildThemeModeStr(len))));
 
     return ListTile(
       title: Text(
@@ -406,6 +408,8 @@ class _SettingPageState extends State<SettingPage> {
         return _s.light;
       case 2:
         return _s.dark;
+      case 3:
+        return 'AMOLED';
       default:
         return _s.auto;
     }