feat(flutter): 增加轮播自动播放与站内通知

lib/core/data/services/notices_controller.dart

@@ -0,0 +1,118 @@
+// Author: fruit.com.cn
+
+import 'package:flutter/foundation.dart';
+
+import '../models/notice.dart';
+import '../remote/api_client.dart';
+import '../repositories/notice_repository.dart';
+
+/// Pagination and state controller for the anonymous notices page.
+class NoticesController extends ChangeNotifier {
+  NoticesController(this._repository, {this.pageSize = 20});
+
+  final NoticeRepository _repository;
+  final int pageSize;
+  final List<AppNotice> _notices = [];
+  int _pageIndex = 0;
+  int _total = 0;
+  bool _disposed = false;
+  bool loading = false;
+  bool loadingMore = false;
+  bool refreshing = false;
+  String? error;
+  String? loadMoreError;
+
+  /// Loaded notices in server order.
+  List<AppNotice> get notices => List.unmodifiable(_notices);
+
+  /// Whether another page is expected from the latest total.
+  bool get hasMore => _notices.length < _total;
+
+  /// Loads the first page.
+  Future<void> load() async {
+    loading = true;
+    error = null;
+    loadMoreError = null;
+    _notify();
+    await _replaceFirstPage();
+    loading = false;
+    _notify();
+  }
+
+  /// Refreshes from page one while keeping the current page visible.
+  Future<void> refresh() async {
+    refreshing = true;
+    error = null;
+    loadMoreError = null;
+    _notify();
+    await _replaceFirstPage();
+    refreshing = false;
+    _notify();
+  }
+
+  /// Appends the next page when loaded count is below total.
+  Future<void> loadMore() async {
+    if (loading || loadingMore || refreshing || !hasMore) return;
+    loadingMore = true;
+    loadMoreError = null;
+    _notify();
+    try {
+      final page = await _repository.page(
+        pageIndex: _pageIndex + 1,
+        pageSize: pageSize,
+      );
+      _appendUnique(page.notices);
+      _pageIndex++;
+      _total = page.total;
+    } catch (failure, stackTrace) {
+      debugPrint('[NoticesController] load more failed: $failure');
+      debugPrintStack(
+        stackTrace: stackTrace,
+        label: '[NoticesController] load more failed',
+      );
+      loadMoreError = _message(failure) ?? 'noticesLoadFailed';
+    } finally {
+      loadingMore = false;
+      _notify();
+    }
+  }
+
+  Future<void> _replaceFirstPage() async {
+    try {
+      final page = await _repository.page(pageIndex: 1, pageSize: pageSize);
+      if (_disposed) return;
+      _notices
+        ..clear()
+        ..addAll(page.notices);
+      _pageIndex = 1;
+      _total = page.total;
+    } catch (failure, stackTrace) {
+      debugPrint('[NoticesController] load failed: $failure');
+      debugPrintStack(
+        stackTrace: stackTrace,
+        label: '[NoticesController] load failed',
+      );
+      if (!_disposed) error = _message(failure) ?? 'noticesLoadFailed';
+    }
+  }
+
+  void _appendUnique(List<AppNotice> incoming) {
+    final ids = _notices.map((notice) => notice.id).toSet();
+    for (final notice in incoming) {
+      if (ids.add(notice.id)) _notices.add(notice);
+    }
+  }
+
+  String? _message(Object failure) =>
+      failure is ApiException ? failure.message : null;
+
+  void _notify() {
+    if (!_disposed) notifyListeners();
+  }
+
+  @override
+  void dispose() {
+    _disposed = true;
+    super.dispose();
+  }
+}