SearchableList.async, async filter function

example/lib/main.dart

@@ -221,14 +221,16 @@ class _ExampleAppState extends State<ExampleApp> {
         await Future.delayed(const Duration(seconds: 5));
         return actors;
       },
-      asyncListFilter: (query, list) {
+      asyncListFilter: (query, list) async {
+        await Future.delayed(const Duration(seconds: 3));
         var result = actors
             .where((element) =>
                 element.name.contains(query) ||
                 element.lastName.contains(query))
             .toList();
         return result;
       },
+      asyncDebounceTime: 200,
       separatorBuilder: (context, index) {
         return Container(
           height: 30,

lib/resources/debouncer.dart

@@ -0,0 +1,20 @@
+import 'dart:async';
+import 'dart:ui';
+
+class Debouncer {
+  final int milliseconds;
+  Timer? _timer;
+
+  Debouncer({required this.milliseconds});
+
+  void run(VoidCallback action) {
+    if (_timer?.isActive ?? false) {
+      _timer?.cancel();
+    }
+    _timer = Timer(Duration(milliseconds: milliseconds), action);
+  }
+
+  void dispose() {
+    _timer?.cancel();
+  }
+}

lib/searchable_listview.dart

@@ -1,7 +1,10 @@
 // ignore_for_file: must_be_immutable
 
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:searchable_listview/resources/arrays.dart';
+import 'package:searchable_listview/resources/debouncer.dart';
 import 'package:searchable_listview/widgets/default_error_widget.dart';
 import 'package:searchable_listview/widgets/default_loading_widget.dart';
 import 'package:searchable_listview/widgets/list_view_rendering.dart';
@@ -82,6 +85,7 @@ class SearchableList<T> extends StatefulWidget {
     required this.asyncListCallback,
     required this.asyncListFilter,
     required this.itemBuilder,
+    this.asyncDebounceTime = 0,
     this.loadingWidget,
     this.errorWidget,
     this.searchTextController,
@@ -271,7 +275,11 @@ class SearchableList<T> extends StatefulWidget {
   /// Callback invoked when filtring the searchable list
   /// used when providing [asyncListCallback]
   /// can't be null when [asyncListCallback] isn't null
-  late List<T> Function(String, List<T>)? asyncListFilter;
+  late Future<List<T>> Function(String, List<T>)? asyncListFilter;
+
+  /// Debouncing time when typing in search field in milliseconds
+  /// Wait [asyncDebounceTime] milliseconds without any new entry before invoking [asyncListFilter]
+  int asyncDebounceTime = 0;
 
   /// Loading widget displayed when [asyncListCallback] is loading
   /// if nothing is provided in [loadingWidget] searchable list will display a [CircularProgressIndicator]
@@ -493,7 +501,9 @@ class _SearchableListState<T> extends State<SearchableList<T>> {
   late List<T> filtredListResult = widget.initialList;
   List<T> filtredAsyncListResult = [];
   String searchText = '';
-  bool dataDownloaded = false;
+  int numberOfRequestLoading = 0;
+  bool asyncError = false;
+  late Debouncer _debouncer;
   List<ExpansionTileController> expansionTileControllers = [];
 
   @override
@@ -513,6 +523,29 @@ class _SearchableListState<T> extends State<SearchableList<T>> {
       }
     });
     widget.searchTextController?.addListener(_textControllerListener);
+
+    if (widget.asyncListCallback != null) {
+      // Load the initial list for the async constructor
+      numberOfRequestLoading = 1;
+      WidgetsBinding.instance.addPostFrameCallback((_) async {
+        try {
+          final result = await widget.asyncListCallback!.call();
+          if (result != null) {
+            filtredAsyncListResult = result;
+          } else {
+            asyncError = true;
+          }
+        } catch (e) {
+          asyncError = true;
+        }
+        if (mounted) {
+          setState(() {
+            numberOfRequestLoading--;
+          });
+        }
+      });
+      _debouncer = Debouncer(milliseconds: widget.asyncDebounceTime);
+    }
   }
 
   @override
@@ -573,7 +606,7 @@ class _SearchableListState<T> extends State<SearchableList<T>> {
               Expanded(
                 child: widget.isExpansionList
                     ? renderExpandableListView()
-                    : (widget.asyncListCallback != null && !dataDownloaded
+                    : (widget.asyncListCallback != null
                         ? renderAsyncListView()
                         : renderSearchableListView()),
               ),
@@ -582,21 +615,13 @@ class _SearchableListState<T> extends State<SearchableList<T>> {
   }
 
   Widget renderAsyncListView() {
-    return FutureBuilder(
-      future: widget.asyncListCallback!.call(),
-      builder: (context, snapshot) {
-        if (snapshot.connectionState == ConnectionState.waiting) {
-          return widget.loadingWidget ?? const DefaultLoadingWidget();
-        }
-        dataDownloaded = true;
-        if (snapshot.data == null) {
-          return widget.errorWidget ?? const DefaultErrorWidget();
-        }
-        asyncListResult = snapshot.data as List<T>;
-        filtredAsyncListResult = asyncListResult;
-        return renderSearchableListView();
-      },
-    );
+    if (asyncError) {
+      return widget.errorWidget ?? const DefaultErrorWidget();
+    }
+    if (numberOfRequestLoading != 0) {
+      return widget.loadingWidget ?? const DefaultLoadingWidget();
+    }
+    return renderSearchableListView();
   }
 
   Widget renderSearchableListView() {
@@ -830,11 +855,25 @@ class _SearchableListState<T> extends State<SearchableList<T>> {
         }
       }
     } else if (widget.asyncListCallback != null) {
-      setState(() {
-        filtredAsyncListResult = widget.asyncListFilter!(
-          value,
-          asyncListResult,
-        );
+      _debouncer.run(() async {
+        if (mounted) {
+          setState(() {
+            numberOfRequestLoading++;
+          });
+        }
+        try {
+          filtredAsyncListResult = await widget.asyncListFilter!(
+            value,
+            asyncListResult,
+          );
+        } catch (e) {
+          asyncError = true;
+        }
+        if (mounted) {
+          setState(() {
+            numberOfRequestLoading--;
+          });
+        }
       });
     } else {
       setState(() {