Make the theme switcher icon change depending on the theme.

android/app/src/main/AndroidManifest.xml

@@ -1,6 +1,6 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <application
-        android:label="calodiary"
+        android:label="Calodiary"
         android:name="${applicationName}"
         android:icon="@mipmap/ic_launcher">
         <activity

lib/perdate_widget.dart

@@ -41,12 +41,18 @@ class _PerDateWidgetState extends State<PerDateWidget> {
         appBar: AppBar(
           title: Text(formattedDate),
           actions: [
-            IconButton(
-              icon: const Icon(Icons.lightbulb),
-              onPressed: () {
-                context.read<ThemeDataBloc>().add(ThemeToggleEvent());
-              },
-            ),
+            BlocBuilder<ThemeDataBloc, ThemeState>(builder: (context, state) {
+              var icon = const Icon(Icons.light_mode);
+              if (state.brightness == 'light') {
+                icon = const Icon(Icons.dark_mode);
+              }
+              return IconButton(
+                icon: icon,
+                onPressed: () {
+                  context.read<ThemeDataBloc>().add(ThemeToggleEvent());
+                },
+              );
+            }),
           ],
         ),
         drawer: const AppDrawer(),