style: 统一下拉与加载指示器

lib/pages/notices/notices_page.dart

@@ -18,6 +18,8 @@ import '../../core/widgets/empty_state.dart';
 import '../../core/widgets/plain_page_scaffold.dart';
 import '../../l10n/app_localizations.dart';
 
+const double _loadMoreThreshold = 240;
+
 /// Anonymous system notice list with pagination and detail dialog.
 class NoticesPage extends StatefulWidget {
   const NoticesPage({super.key});
@@ -111,29 +113,55 @@ class _NoticesPageState extends State<NoticesPage> {
     }
     return AppPullToRefresh(
       onRefresh: _controller.refresh,
-      child: ListView.separated(
-        key: const Key('notices-list'),
-        physics: AppPullToRefresh.physics,
-        padding: const EdgeInsets.fromLTRB(16, 12, 16, 28),
-        itemCount: _controller.notices.length + 1,
-        separatorBuilder: (_, _) => const SizedBox(height: 10),
-        itemBuilder: (context, index) {
-          if (index == _controller.notices.length) return _footer(l10n);
-          final notice = _controller.notices[index];
-          return _NoticeTile(
-            notice: notice,
-            onTap: () => _showDetails(notice, l10n),
-          );
-        },
+      child: NotificationListener<ScrollNotification>(
+        onNotification: _onScroll,
+        child: ListView.separated(
+          key: const Key('notices-list'),
+          physics: AppPullToRefresh.physics,
+          padding: const EdgeInsets.fromLTRB(16, 12, 16, 28),
+          itemCount: _controller.notices.length + 1,
+          separatorBuilder: (_, _) => const SizedBox(height: 10),
+          itemBuilder: (context, index) {
+            if (index == _controller.notices.length) return _footer(l10n);
+            final notice = _controller.notices[index];
+            return _NoticeTile(
+              notice: notice,
+              onTap: () => _showDetails(notice, l10n),
+            );
+          },
+        ),
       ),
     );
   }
 
+  bool _onScroll(ScrollNotification notification) {
+    if (notification.depth != 0 ||
+        !_controller.hasMore ||
+        _controller.loadingMore) {
+      return false;
+    }
+    if (notification.metrics.extentAfter > _loadMoreThreshold) return false;
+    if (notification is ScrollUpdateNotification ||
+        notification is ScrollEndNotification ||
+        notification is OverscrollNotification) {
+      unawaited(_controller.loadMore());
+    }
+    return false;
+  }
+
   Widget _footer(AppLocalizations l10n) {
     if (_controller.loadingMore) {
-      return const Padding(
-        padding: EdgeInsets.symmetric(vertical: 12),
-        child: Center(child: CircularProgressIndicator()),
+      return const SizedBox(
+        height: AppDimens.loadMoreIndicatorHeight,
+        child: Center(
+          child: SizedBox.square(
+            dimension: AppDimens.refreshSpinnerSize,
+            child: CircularProgressIndicator(
+              strokeWidth: AppDimens.refreshSpinnerStroke,
+              color: AppColors.textPrimary,
+            ),
+          ),
+        ),
       );
     }
     if (_controller.loadMoreError != null) {
@@ -143,14 +171,7 @@ class _NoticesPageState extends State<NoticesPage> {
         label: Text(l10n.retry),
       );
     }
-    if (_controller.hasMore) {
-      return TextButton(
-        key: const Key('notices-load-more'),
-        onPressed: _controller.loadMore,
-        child: Text(l10n.loadMore),
-      );
-    }
-    return const SizedBox(height: 8);
+    return const SizedBox.shrink();
   }
 
   Future<void> _showDetails(AppNotice notice, AppLocalizations l10n) {