refactor(empty-state): 空状态支持内容居中

lib/pages/watch_records/watch_records_page.dart

@@ -26,7 +26,6 @@ import 'widgets/watch_record_card.dart';
 
 const double _pageHorizontal = 14;
 const double _statsFontSize = 12;
-const double _emptyListHeight = 360;
 const double _loadMoreThreshold = 240;
 
 /// 独立观看记录页。
@@ -113,31 +112,22 @@ class _WatchRecordsBodyState extends State<_WatchRecordsBody> {
       );
     }
     if (controller.error != null && controller.records.isEmpty) {
-      return _refreshable(
-        children: [
-          SizedBox(
-            height: _emptyListHeight,
-            child: _FailureState(
-              message: errorText(l10n, controller.error, l10n.progressError),
-              onRetry: controller.load,
-            ),
-          ),
-        ],
+      return _refreshableState(
+        child: _FailureState(
+          message: errorText(l10n, controller.error, l10n.progressError),
+          onRetry: controller.load,
+        ),
       );
     }
     if (controller.records.isEmpty) {
-      return _refreshable(
-        children: [
-          SizedBox(
-            height: _emptyListHeight,
-            child: EmptyState(
-              key: const Key('watch-records-empty'),
-              icon: Icons.history_rounded,
-              title: l10n.noWatchRecords,
-              subtitle: l10n.emptyHint,
-            ),
-          ),
-        ],
+      return _refreshableState(
+        child: EmptyState(
+          key: const Key('watch-records-empty'),
+          icon: Icons.history_rounded,
+          title: l10n.noWatchRecords,
+          subtitle: l10n.emptyHint,
+          stretchContent: true,
+        ),
       );
     }
     return _refreshable(
@@ -184,6 +174,17 @@ class _WatchRecordsBodyState extends State<_WatchRecordsBody> {
     );
   }
 
+  Widget _refreshableState({required Widget child}) {
+    return AppPullToRefresh(
+      onRefresh: controller.load,
+      child: CustomScrollView(
+        key: const Key('watch-records-empty-scroll'),
+        physics: AppPullToRefresh.physics,
+        slivers: [SliverFillRemaining(hasScrollBody: false, child: child)],
+      ),
+    );
+  }
+
   bool _onScroll(ScrollNotification notification) {
     if (notification.depth != 0) return false;
     final reachedBottom =
@@ -303,6 +304,7 @@ class _FailureState extends StatelessWidget {
       actionLabel: l10n.retry,
       actionKey: const Key('watch-records-retry'),
       onAction: () => unawaited(onRetry()),
+      stretchContent: true,
     );
   }
 }