feat: 增加搜索结果下拉刷新

lib/pages/discover/discover_logic.dart

@@ -61,6 +61,14 @@ class DiscoverLogic extends ChangeNotifier {
     if (query.isNotEmpty) unawaited(_runSearch(query));
   }
 
+  /// 用当前关键词重新请求第一页；刷新期间保留旧结果。
+  Future<void> refreshSearch() async {
+    final query = search.text.trim();
+    if (query.isEmpty) return;
+    _searchTimer?.cancel();
+    await _runSearch(query, preserveResults: true);
+  }
+
   void _resetSearch() {
     _searchTimer?.cancel();
     _searchRequest++;
@@ -85,7 +93,7 @@ class DiscoverLogic extends ChangeNotifier {
     _searchTimer = Timer(searchDebounce, () => unawaited(_runSearch(query)));
   }
 
-  Future<void> _runSearch(String query) async {
+  Future<void> _runSearch(String query, {bool preserveResults = false}) async {
     final repository = searchRepository;
     if (repository == null) return;
     final request = ++_searchRequest;
@@ -101,9 +109,17 @@ class DiscoverLogic extends ChangeNotifier {
       if (request != _searchRequest) return;
       searchResults = result.list;
     } on ApiException catch (exception) {
-      _applySearchError(request, exception.message);
+      _applySearchError(
+        request,
+        exception.message,
+        preserveResults: preserveResults,
+      );
     } catch (_) {
-      _applySearchError(request, 'searchFailed');
+      _applySearchError(
+        request,
+        'searchFailed',
+        preserveResults: preserveResults,
+      );
     } finally {
       if (request == _searchRequest) {
         searchLoading = false;
@@ -112,8 +128,13 @@ class DiscoverLogic extends ChangeNotifier {
     }
   }
 
-  void _applySearchError(int request, String message) {
+  void _applySearchError(
+    int request,
+    String message, {
+    bool preserveResults = false,
+  }) {
     if (request != _searchRequest) return;
+    if (preserveResults && searchResults.isNotEmpty) return;
     searchError = message;
     searchResults = const [];
   }