feat(flutter): 剧场页搜索与吸顶筛选精致化

lib/pages/discover/discover_view.dart

@@ -31,6 +31,8 @@ const double _categoryTabHeight = 44;
 const double _categoryTabGap = 20;
 const double _categorySelectedFontSize = 16;
 const double _categoryFontSize = 15;
+const double _stickyHeaderHeight = 102;
+const Duration _stickyHeaderTransition = Duration(milliseconds: 200);
 
 /// K28-A2 剧场页：搜索、分类/语言 chips 与双列剧库。
 class DiscoverPage extends StatefulWidget {
@@ -53,6 +55,7 @@ class DiscoverPage extends StatefulWidget {
 
 class _DiscoverPageState extends State<DiscoverPage> {
   late final DiscoverLogic logic;
+  bool _headerScrolled = false;
 
   bool get embedded => widget.callbacks.embedded;
 
@@ -60,9 +63,17 @@ class _DiscoverPageState extends State<DiscoverPage> {
   void initState() {
     super.initState();
     logic = DiscoverBinding().create(search: context.read<SearchRepository>());
+    logic.scroll.addListener(_onScroll);
     if (widget.focusSearch) _focusOnFirstFrame();
   }
 
+  void _onScroll() {
+    final scrolled = logic.scroll.hasClients && logic.scroll.offset > 0;
+    if (scrolled != _headerScrolled) {
+      setState(() => _headerScrolled = scrolled);
+    }
+  }
+
   void _focusOnFirstFrame() {
     WidgetsBinding.instance.addPostFrameCallback((_) {
       if (mounted && widget.active) logic.openSearch();
@@ -82,6 +93,7 @@ class _DiscoverPageState extends State<DiscoverPage> {
 
   @override
   void dispose() {
+    logic.scroll.removeListener(_onScroll);
     logic.dispose();
     super.dispose();
   }
@@ -124,20 +136,73 @@ class _DiscoverPageState extends State<DiscoverPage> {
   }
 
   Widget _feed(AppLocalizations l10n, CategoryController categories) {
+    final showHeader = _showStickyHeader(categories);
     return GestureDetector(
       behavior: HitTestBehavior.translucent,
       onTap: logic.searchFocus.unfocus,
-      child: RefreshIndicator(
-        key: const Key('discover-refresh'),
-        color: AppColors.blue,
-        backgroundColor: AppColors.card,
-        onRefresh: categories.load,
-        child: ListView(
-          controller: logic.scroll,
-          physics: const AlwaysScrollableScrollPhysics(),
-          padding: const EdgeInsets.only(bottom: AppDimens.spaceXl),
-          children: _content(l10n, categories),
+      child: Stack(
+        children: [
+          Positioned.fill(
+            child: RefreshIndicator(
+              key: const Key('discover-refresh'),
+              color: AppColors.blue,
+              backgroundColor: AppColors.card,
+              strokeWidth: 2,
+              edgeOffset: _stickyHeaderHeight + 8,
+              onRefresh: categories.load,
+              child: ListView(
+                controller: logic.scroll,
+                physics: const AlwaysScrollableScrollPhysics(),
+                padding: EdgeInsets.only(
+                  top: showHeader ? _stickyHeaderHeight : 0,
+                  bottom: AppDimens.spaceXl,
+                ),
+                children: _content(l10n, categories),
+              ),
+            ),
+          ),
+          if (showHeader)
+            Positioned(
+              top: 0,
+              left: 0,
+              right: 0,
+              child: _stickyHeader(l10n, categories),
+            ),
+        ],
+      ),
+    );
+  }
+
+  bool _showStickyHeader(CategoryController categories) {
+    if (logic.hasSearchQuery || categories.error != null) return false;
+    return !(categories.loading && categories.feed.sections.isEmpty);
+  }
+
+  Widget _stickyHeader(AppLocalizations l10n, CategoryController categories) {
+    return AnimatedContainer(
+      key: const Key('theater-sticky-header'),
+      duration: _stickyHeaderTransition,
+      curve: Curves.easeOut,
+      decoration: BoxDecoration(
+        color: _headerScrolled ? AppColors.ink : Colors.transparent,
+        border: Border(
+          bottom: BorderSide(
+            color: _headerScrolled ? AppColors.border : Colors.transparent,
+          ),
         ),
+        boxShadow: _headerScrolled
+            ? const [
+                BoxShadow(
+                  color: Color(0x14000000),
+                  blurRadius: 8,
+                  offset: Offset(0, 2),
+                ),
+              ]
+            : const [],
+      ),
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [_categoryTabs(l10n, categories), _toolbar(l10n, categories)],
       ),
     );
   }
@@ -183,8 +248,6 @@ class _DiscoverPageState extends State<DiscoverPage> {
         ? categories.feed.dramas
         : categories.dramasOf(logic.selectedCategoryId!);
     return [
-      _categoryTabs(l10n, categories),
-      _toolbar(l10n, categories),
       if (dramas.isEmpty)
         Padding(
           padding: const EdgeInsets.symmetric(vertical: 40),