feat(ObserverWidget): make ObserverWidget listenable

Author: LinXunFeng

lib/src/common/observer_listener.dart

@@ -0,0 +1,30 @@
+/*
+ * @Author: LinXunFeng [email protected]
+ * @Repo: https://github.com/fluttercandies/flutter_scrollview_observer
+ * @Date: 2024-10-27 17:16:57
+ */
+
+import 'dart:collection';
+
+import 'package:flutter/material.dart';
+
+import 'package:scrollview_observer/src/common/models/observe_model.dart';
+import 'package:scrollview_observer/src/common/observer_typedef.dart';
+
+class ObserverListenerEntry<M extends ObserveModel>
+    extends LinkedListEntry<ObserverListenerEntry<M>> {
+  ObserverListenerEntry({
+    required this.context,
+    required this.onObserve,
+    required this.onObserveAll,
+  });
+
+  /// The context of the listener.
+  final BuildContext? context;
+
+  /// The callback of getting observed result.
+  final OnObserveCallback<M>? onObserve;
+
+  /// The callback of getting observed result map.
+  final OnObserveAllCallback<M>? onObserveAll;
+}

lib/src/common/observer_typedef.dart

@@ -4,13 +4,37 @@
  * @Date: 2022-12-04 15:57:38
  */
 
+import 'package:flutter/material.dart';
+import 'package:scrollview_observer/src/common/models/observe_model.dart';
 import 'package:scrollview_observer/src/common/models/observe_scroll_to_index_result_model.dart';
+import 'package:scrollview_observer/src/sliver/models/sliver_viewport_observe_model.dart';
 
 /// Called when the ObserverController prepare to scroll to index with
 /// [ObservePrepareScrollToIndexModel].
 typedef ObserverOnPrepareScrollToIndex = Future<bool> Function(
     ObservePrepareScrollToIndexModel);
 
+/// The callback type of getting observed result for first sliver.
+///
+/// Corresponds to onObserve.
+typedef OnObserveCallback<M extends ObserveModel> = void Function(
+  M result,
+);
+
+/// The callback type of getting observed result map.
+///
+/// Corresponds to onObserveAll.
+typedef OnObserveAllCallback<M extends ObserveModel> = void Function(
+  Map<BuildContext, M> resultMap,
+);
+
+/// The callback type of getting all slivers those are displayed in viewport.
+///
+/// Corresponds to onObserveViewport.
+typedef OnObserveViewportCallback = void Function(
+  SliverViewportObserveModel result,
+);
+
 /// Define type that auto trigger observe.
 enum ObserverAutoTriggerObserveType {
   scrollStart,