improve ui

lib/components/appbar.dart

@@ -73,8 +73,12 @@ class _AppbarState extends State<Appbar> {
 
   @override
   Widget build(BuildContext context) {
-    var content = SizedBox(
-      height: _kAppBarHeight,
+    var content = Container(
+      decoration: BoxDecoration(
+        color: widget.backgroundColor ??
+            context.colorScheme.surface.withOpacity(0.72),
+      ),
+      height: _kAppBarHeight + context.padding.top,
       child: Row(
         children: [
           const SizedBox(width: 8),
@@ -102,17 +106,12 @@ class _AppbarState extends State<Appbar> {
             width: 8,
           )
         ],
-      ),
-    ).paddingTop(context.padding.top);
-    if (widget.backgroundColor != Colors.transparent) {
-      return Material(
-        elevation: (_scrolledUnder && context.width < changePoint) ? 1 : 0,
-        surfaceTintColor: Theme.of(context).colorScheme.surfaceTint,
-        color: widget.backgroundColor ?? Theme.of(context).colorScheme.surface,
-        child: content,
-      );
-    }
-    return content;
+      ).paddingTop(context.padding.top),
+    );
+    return BlurEffect(
+      blur: _scrolledUnder ? 15 : 0,
+      child: content,
+    );
   }
 }
 
@@ -192,7 +191,7 @@ class _MySliverAppBarDelegate extends SliverPersistentHeaderDelegate {
                         )
                       : const SizedBox()),
               const SizedBox(
-                width: 24,
+                width: 16,
               ),
               Expanded(
                 child: DefaultTextStyle(

lib/components/comic.dart

@@ -735,6 +735,12 @@ class ComicListState extends State<ComicList> {
   }
 
   Future<void> _loadPage(int page) async {
+    if (widget.loadPage == null && widget.loadNext == null) {
+      _error = "loadPage and loadNext can't be null at the same time";
+      Future.microtask(() {
+        setState(() {});
+      });
+    }
     if (_loading[page] == true) {
       return;
     }
@@ -790,9 +796,6 @@ class ComicListState extends State<ComicList> {
 
   @override
   Widget build(BuildContext context) {
-    if (widget.loadPage == null && widget.loadNext == null) {
-      throw Exception("loadPage and loadNext can't be null at the same time");
-    }
     if (_error != null) {
       return Column(
         children: [
@@ -814,19 +817,27 @@ class ComicListState extends State<ComicList> {
     }
     if (_data[_page] == null) {
       _loadPage(_page);
-      return const Center(
-        child: CircularProgressIndicator(),
+      return Column(
+        children: [
+          if (widget.errorLeading != null) widget.errorLeading!,
+          const Expanded(
+            child: Center(
+              child: CircularProgressIndicator(),
+            ),
+          ),
+        ],
       );
     }
     return SmoothCustomScrollView(
       slivers: [
         if (widget.leadingSliver != null) widget.leadingSliver!,
-        _buildSliverPageSelector(),
+        if (_maxPage != 1) _buildSliverPageSelector(),
         SliverGridComics(
           comics: _data[_page] ?? const [],
           menuBuilder: widget.menuBuilder,
         ),
-        if (_data[_page]!.length > 6) _buildSliverPageSelector(),
+        if (_data[_page]!.length > 6 && _maxPage != 1)
+          _buildSliverPageSelector(),
         if (widget.trailingSliver != null) widget.trailingSliver!,
       ],
     );

lib/components/navigation_bar.dart

@@ -148,7 +148,7 @@ class _NaviPaneState extends State<NaviPane>
     return _NaviPopScope(
       action: () {
         if (App.mainNavigatorKey!.currentState!.canPop()) {
-          App.mainNavigatorKey!.currentState!.pop();
+          App.mainNavigatorKey!.currentState!.maybePop();
         } else {
           SystemNavigator.pop();
         }
@@ -627,16 +627,9 @@ class _NaviPopScope extends StatelessWidget {
         ? child
         : PopScope(
             canPop: App.isAndroid ? false : true,
-            // flutter <3.24.0 api
-            onPopInvoked: (value) {
-              action();
-            },
-            /*
-            flutter >=3.24.0 api
             onPopInvokedWithResult: (value, result) {
               action();
             },
-            */
             child: child,
           );
     if (popGesture) {