fix(flutter): 优化二级页面返回按钮样式

lib/core/widgets/subpage_header.dart

@@ -7,14 +7,21 @@ import '../theme/app_colors.dart';
 const double _height = 52;
 const double _heightWithSubtitle = 64;
 const double _horizontal = 14;
-const double _backSize = 36;
+const double _backSize = 40;
 const double _backGap = 12;
 const double _titleFontSize = 18;
 const double _subtitleFontSize = 12;
 const double _actionGap = 8;
-const double _iconSize = 20;
+const double _iconSize = 22;
+const double _iconWeight = 600;
+const double _borderWidth = 1;
+const double _shadowBlur = 8;
+const Color _lightShadowColor = Color(0x14000000);
+const Color _darkBackground = Color(0x59000000);
+const Color _darkShadowColor = Color(0x33000000);
+const Offset _lightShadowOffset = Offset(0, 2);
 
-/// 二级页面统一返回按钮，浅色页使用 card 圆底，深色页使用透明底。
+/// 二级页面统一返回按钮，浅色页使用白底描边，深色页使用半透明黑底。
 class AppSubpageBackButton extends StatelessWidget {
   const AppSubpageBackButton({
     super.key,
@@ -35,16 +42,40 @@ class AppSubpageBackButton extends StatelessWidget {
       height: _backSize,
       child: Tooltip(
         message: MaterialLocalizations.of(context).backButtonTooltip,
-        child: Material(
-          color: dark ? Colors.transparent : AppColors.card,
-          shape: const CircleBorder(),
-          clipBehavior: Clip.antiAlias,
-          child: InkWell(
-            onTap: onBack ?? () => Navigator.of(context).maybePop(),
-            child: Icon(
-              Icons.chevron_left_rounded,
-              color: dark ? Colors.white : AppColors.onSurface,
-              size: _iconSize,
+        child: DecoratedBox(
+          key: const Key('subpage-back-shadow'),
+          decoration: BoxDecoration(
+            shape: BoxShape.circle,
+            boxShadow: [
+              BoxShadow(
+                color: dark ? _darkShadowColor : _lightShadowColor,
+                blurRadius: _shadowBlur,
+                offset: dark ? Offset.zero : _lightShadowOffset,
+              ),
+            ],
+          ),
+          child: Material(
+            color: dark ? _darkBackground : AppColors.card,
+            shape: CircleBorder(
+              side: dark
+                  ? BorderSide.none
+                  : const BorderSide(
+                      color: AppColors.border,
+                      width: _borderWidth,
+                    ),
+            ),
+            clipBehavior: Clip.antiAlias,
+            child: InkWell(
+              customBorder: const CircleBorder(),
+              onTap: onBack ?? () => Navigator.of(context).maybePop(),
+              child: Center(
+                child: Icon(
+                  Icons.chevron_left_rounded,
+                  color: dark ? Colors.white : AppColors.onSurface,
+                  size: _iconSize,
+                  weight: _iconWeight,
+                ),
+              ),
             ),
           ),
         ),

test/core/subpage_header_test.dart

@@ -23,7 +23,7 @@ void main() {
     expect(tester.getSize(find.byKey(const Key('subpage-header'))).height, 52);
     expect(
       tester.getSize(find.byKey(const Key('sample-back'))),
-      const Size(36, 36),
+      const Size(40, 40),
     );
     final title = tester.widget<Text>(find.byKey(const Key('subpage-title')));
     expect(title.style?.fontSize, 18);
@@ -32,6 +32,24 @@ void main() {
     final back = tester.getRect(find.byKey(const Key('sample-back')));
     final titleRect = tester.getRect(find.byKey(const Key('subpage-title')));
     expect(titleRect.left - back.right, closeTo(12, 0.5));
+    final surface = tester.widget<Material>(
+      find.descendant(
+        of: find.byKey(const Key('sample-back')),
+        matching: find.byType(Material),
+      ),
+    );
+    expect(surface.color, AppColors.card);
+    expect((surface.shape! as CircleBorder).side.color, AppColors.border);
+    final shadow =
+        tester
+                .widget<DecoratedBox>(
+                  find.byKey(const Key('subpage-back-shadow')),
+                )
+                .decoration
+            as BoxDecoration;
+    expect(shadow.boxShadow!.single.color, const Color(0x14000000));
+    expect(shadow.boxShadow!.single.blurRadius, 8);
+    expect(shadow.boxShadow!.single.offset, const Offset(0, 2));
   });
 
   testWidgets('should_use_64_height_when_subtitle_exists', (tester) async {
@@ -52,7 +70,7 @@ void main() {
     expect(find.byKey(const Key('subpage-subtitle')), findsOneWidget);
   });
 
-  testWidgets('should_use_transparent_dark_back_button', (tester) async {
+  testWidgets('should_use_translucent_dark_back_button', (tester) async {
     await tester.pumpWidget(
       MaterialApp(
         theme: AppTheme.light(),
@@ -79,8 +97,18 @@ void main() {
         matching: find.byIcon(Icons.chevron_left_rounded),
       ),
     );
-    expect(material.color, Colors.transparent);
+    expect(material.color, const Color(0x59000000));
     expect(icon.color, Colors.white);
-    expect(icon.size, 20);
+    expect(icon.size, 22);
+    expect(icon.weight, 600);
+    final shadow =
+        tester
+                .widget<DecoratedBox>(
+                  find.byKey(const Key('subpage-back-shadow')),
+                )
+                .decoration
+            as BoxDecoration;
+    expect(shadow.boxShadow!.single.color, const Color(0x33000000));
+    expect(shadow.boxShadow!.single.blurRadius, 8);
   });
 }

test/discover/filter_page_test.dart

@@ -186,7 +186,7 @@ final List<Drama> _filterDramas = [
 ];
 
 void _expectUnifiedHeader(WidgetTester tester, Key backKey) {
-  expect(tester.getSize(find.byKey(backKey)), const Size(36, 36));
+  expect(tester.getSize(find.byKey(backKey)), const Size(40, 40));
   final title = tester.widget<Text>(find.byKey(const Key('subpage-title')));
   expect(title.style?.fontSize, 18);
   expect(title.style?.fontWeight, FontWeight.w800);

test/discover/theater_pages_test.dart

@@ -220,7 +220,7 @@ List<Drama> _rankDramas(int count) => [
 ];
 
 void _expectUnifiedHeader(WidgetTester tester, Key backKey) {
-  expect(tester.getSize(find.byKey(backKey)), const Size(36, 36));
+  expect(tester.getSize(find.byKey(backKey)), const Size(40, 40));
   final title = tester.widget<Text>(find.byKey(const Key('subpage-title')));
   expect(title.style?.fontSize, 18);
   expect(title.style?.fontWeight, FontWeight.w800);

test/drama_detail/drama_detail_view_test.dart

@@ -58,6 +58,21 @@ void main() {
       tester.getSize(find.byKey(const Key('detail-poster'))),
       const Size(96, 128),
     );
+    expect(
+      tester.getSize(find.byKey(const Key('detail-back'))),
+      const Size(40, 40),
+    );
+    expect(
+      tester
+          .widget<Material>(
+            find.descendant(
+              of: find.byKey(const Key('detail-back')),
+              matching: find.byType(Material),
+            ),
+          )
+          .color,
+      const Color(0x59000000),
+    );
     expect(
       tester
           .widget<Text>(find.byKey(const Key('detail-title')))

test/mine/settings_page_test.dart

@@ -54,7 +54,7 @@ void main() {
     expect(find.byKey(const Key('settings-page')), findsOneWidget);
     expect(
       tester.getSize(find.byKey(const Key('settings-back'))),
-      const Size(36, 36),
+      const Size(40, 40),
     );
     final title = tester.widget<Text>(find.byKey(const Key('subpage-title')));
     expect(title.style?.fontSize, 18);

test/notice/notices_entry_test.dart

@@ -54,7 +54,7 @@ void main() {
     expect(find.byKey(const Key('notices-page')), findsOneWidget);
     expect(
       tester.getSize(find.byKey(const Key('notices-back'))),
-      const Size(36, 36),
+      const Size(40, 40),
     );
     final title = tester.widget<Text>(find.byKey(const Key('subpage-title')));
     expect(title.style?.fontSize, 18);