feat(flutter): 增加轮播自动播放与站内通知

lib/pages/discover/widgets/cover_carousel.dart

@@ -1,7 +1,12 @@
+import 'dart:async';
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';
+import '../../../core/theme/app_colors.dart';
 import '../../../core/widgets/remote_image.dart';
+import '../../../l10n/app_localizations.dart';
+
+const Duration _autoPlayInterval = Duration(milliseconds: 4500);
 
 class CoverItem {
   const CoverItem({
@@ -19,9 +24,10 @@ class CoverItem {
 
 /// Full-bleed posters that turn as faces of a cube. Titles sit on the image.
 class CoverCarousel extends StatefulWidget {
-  const CoverCarousel({super.key, required this.items});
+  const CoverCarousel({super.key, required this.items, this.active = true});
 
   final List<CoverItem> items;
+  final bool active;
 
   @override
   State<CoverCarousel> createState() => _CoverCarouselState();
@@ -36,6 +42,8 @@ class _CoverCarouselState extends State<CoverCarousel>
   int? _pointer;
   double _drag = 0;
   double _dragPage = 0;
+  Timer? _autoTimer;
+  bool _tickerEnabled = true;
 
   @override
   void initState() {
@@ -45,34 +53,93 @@ class _CoverCarouselState extends State<CoverCarousel>
 
   @override
   void dispose() {
+    _autoTimer?.cancel();
     _snap.dispose();
     super.dispose();
   }
 
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    final enabled = TickerMode.valuesOf(context).enabled;
+    if (enabled != _tickerEnabled) {
+      _tickerEnabled = enabled;
+      _syncAutoTimer();
+    } else if (_autoTimer == null) {
+      _syncAutoTimer();
+    }
+  }
+
+  @override
+  void didUpdateWidget(covariant CoverCarousel oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    if (_page > _last) _page = _last;
+    if (oldWidget.items.length != widget.items.length ||
+        oldWidget.active != widget.active) {
+      _syncAutoTimer();
+    }
+  }
+
   double get _last => math.max(0, widget.items.length - 1).toDouble();
 
   void _onSnap() {
+    if (!mounted) return;
     final t = Curves.easeOutCubic.transform(_snap.value);
     setState(() => _page = _from + (_to - _from) * t);
   }
 
   void _turnTo(double target) {
+    if (!mounted || widget.items.isEmpty) return;
     _from = _page;
     _to = target.clamp(0, _last);
     _snap.duration = const Duration(milliseconds: 420);
     _snap.forward(from: 0);
   }
 
+  void _syncAutoTimer() {
+    _autoTimer?.cancel();
+    _autoTimer = null;
+    if (!mounted ||
+        !widget.active ||
+        !_tickerEnabled ||
+        widget.items.length <= 1) {
+      return;
+    }
+    _autoTimer = Timer.periodic(_autoPlayInterval, (_) {
+      if (!mounted || _pointer != null || !widget.active || !_tickerEnabled) {
+        return;
+      }
+      final current = _page.round().clamp(0, _last.toInt());
+      if (current >= _last.toInt()) {
+        setState(() => _page = 0);
+      } else {
+        _turnTo((current + 1).toDouble());
+      }
+    });
+  }
+
   @override
   Widget build(BuildContext context) {
+    if (widget.items.isEmpty) return const SizedBox.shrink();
+    final current = _page.round().clamp(0, widget.items.length - 1);
+    final l10n = AppLocalizations.of(context)!;
     return LayoutBuilder(
       builder: (context, constraints) {
         final width = constraints.maxWidth;
         final height = math.min(width * 0.52, 210).toDouble();
-        return SizedBox(
-          width: double.infinity,
-          height: height,
-          child: _stage(width),
+        return Semantics(
+          container: true,
+          label: l10n.carouselSemantics(current + 1, widget.items.length),
+          child: SizedBox(
+            width: double.infinity,
+            height: height,
+            child: Stack(
+              children: [
+                Positioned.fill(child: _stage(width)),
+                _indicator(l10n, current),
+              ],
+            ),
+          ),
         );
       },
     );
@@ -82,6 +149,8 @@ class _CoverCarouselState extends State<CoverCarousel>
     return Listener(
       behavior: HitTestBehavior.opaque,
       onPointerDown: (event) {
+        _autoTimer?.cancel();
+        _autoTimer = null;
         _snap.stop();
         _pointer = event.pointer;
         _drag = 0;
@@ -98,11 +167,13 @@ class _CoverCarouselState extends State<CoverCarousel>
         if (event.pointer != _pointer) return;
         _pointer = null;
         _turnTo(_page.roundToDouble());
+        _syncAutoTimer();
       },
       onPointerCancel: (event) {
         if (event.pointer != _pointer) return;
         _pointer = null;
         _turnTo(_page.roundToDouble());
+        _syncAutoTimer();
       },
       child: ClipRect(
         child: Stack(
@@ -113,6 +184,35 @@ class _CoverCarouselState extends State<CoverCarousel>
     );
   }
 
+  Widget _indicator(AppLocalizations l10n, int current) {
+    return Positioned(
+      left: 0,
+      right: 0,
+      bottom: 8,
+      child: Semantics(
+        label: l10n.carouselSemantics(current + 1, widget.items.length),
+        child: Row(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            for (var index = 0; index < widget.items.length; index++)
+              Container(
+                key: Key('carousel-dot-$index'),
+                width: 6,
+                height: 6,
+                margin: const EdgeInsets.symmetric(horizontal: 3),
+                decoration: BoxDecoration(
+                  shape: BoxShape.circle,
+                  color: index == current
+                      ? AppColors.onPrimary
+                      : AppColors.muted.withValues(alpha: 0.4),
+                ),
+              ),
+          ],
+        ),
+      ),
+    );
+  }
+
   List<int> get _visible {
     final first = _page.floor();
     final indexes = <int>[first, first + 1];
@@ -154,7 +254,11 @@ class _CoverCarouselState extends State<CoverCarousel>
     return Stack(
       fit: StackFit.expand,
       children: [
-        RemoteImage(item.image),
+        RemoteImage(
+          item.image,
+          showFallbackIcon: true,
+          fallbackIconKey: const Key('carousel-image-fallback'),
+        ),
         const DecoratedBox(
           decoration: BoxDecoration(
             gradient: LinearGradient(
@@ -168,7 +272,7 @@ class _CoverCarouselState extends State<CoverCarousel>
         Positioned(
           left: 20,
           right: 20,
-          bottom: 22,
+          bottom: 30,
           child: Column(
             crossAxisAlignment: CrossAxisAlignment.start,
             children: [