Provide an optional choice for the caller: if the page disposal scena…

packages/visibility_detector/lib/src/visibility_detector.dart

@@ -9,6 +9,7 @@ import 'dart:math' show max;
 import 'package:flutter/widgets.dart';
 
 import 'render_visibility_detector.dart';
+import 'visibility_detector_element.dart';
 
 /// A [VisibilityDetector] widget fires a specified callback when the widget
 /// changes visibility.
@@ -31,13 +32,26 @@ class VisibilityDetector extends SingleChildRenderObjectWidget {
     required Key key,
     required Widget child,
     required this.onVisibilityChanged,
+    this.isChangedOnDispose = true,
   })  : assert(key != null),
         assert(child != null),
         super(key: key, child: child);
 
   /// The callback to invoke when this widget's visibility changes.
   final VisibilityChangedCallback? onVisibilityChanged;
 
+  /// Indicates whether the visibility change callback should be triggered
+  /// when the widget is disposed.
+  ///
+  /// When set to true, the `onVisibilityChanged` callback will be invoked
+  /// even after the widget has been removed from the widget tree. This can
+  /// be useful for scenarios where you need to perform cleanup or notify
+  /// other parts of the application about the visibility state before
+  /// the widget is completely disposed of.
+  ///
+  /// Default value is true.
+  final bool isChangedOnDispose;
+
   /// See [RenderObjectWidget.createRenderObject].
   @override
   RenderVisibilityDetector createRenderObject(BuildContext context) {
@@ -54,6 +68,22 @@ class VisibilityDetector extends SingleChildRenderObjectWidget {
     assert(renderObject.key == key);
     renderObject.onVisibilityChanged = onVisibilityChanged;
   }
+
+  /// See [RenderObjectWidget.createElement].
+  ///
+  /// This override creates a [VisibilityDetectorElement] configured with
+  /// the current [VisibilityDetector] widget instance. The created element
+  /// maintains the association between this widget and its corresponding
+  /// [RenderVisibilityDetector] render object.
+  ///
+  /// Framework automatically calls this method when inflating the widget tree.
+  @override
+  SingleChildRenderObjectElement createElement() {
+    if (isChangedOnDispose) {
+      return super.createElement();
+    }
+    return VisibilityDetectorElement(this);
+  }
 }
 
 class SliverVisibilityDetector extends SingleChildRenderObjectWidget {
@@ -68,13 +98,26 @@ class SliverVisibilityDetector extends SingleChildRenderObjectWidget {
     required Key key,
     required Widget sliver,
     required this.onVisibilityChanged,
+    this.isChangedOnDispose = true,
   })  : assert(key != null),
         assert(sliver != null),
         super(key: key, child: sliver);
 
   /// The callback to invoke when this widget's visibility changes.
   final VisibilityChangedCallback? onVisibilityChanged;
 
+  /// Indicates whether the visibility change callback should be triggered
+  /// when the widget is disposed.
+  ///
+  /// When set to true, the `onVisibilityChanged` callback will be invoked
+  /// even after the widget has been removed from the widget tree. This can
+  /// be useful for scenarios where you need to perform cleanup or notify
+  /// other parts of the application about the visibility state before
+  /// the widget is completely disposed of.
+  ///
+  /// Default value is true.
+  final bool isChangedOnDispose;
+
   /// See [RenderObjectWidget.createRenderObject].
   @override
   RenderSliverVisibilityDetector createRenderObject(BuildContext context) {
@@ -91,6 +134,15 @@ class SliverVisibilityDetector extends SingleChildRenderObjectWidget {
     assert(renderObject.key == key);
     renderObject.onVisibilityChanged = onVisibilityChanged;
   }
+
+  /// See [RenderObjectWidget.createElement].
+  @override
+  SingleChildRenderObjectElement createElement() {
+    if (isChangedOnDispose) {
+      return super.createElement();
+    }
+    return SliverVisibilityDetectorElement(this);
+  }
 }
 
 typedef VisibilityChangedCallback = void Function(VisibilityInfo info);

packages/visibility_detector/lib/src/visibility_detector_element.dart

@@ -0,0 +1,73 @@
+import 'package:flutter/widgets.dart';
+
+import 'render_visibility_detector.dart';
+import 'visibility_detector.dart';
+
+/// An [Element] that manages the lifecycle of the associated [RenderVisibilityDetector].
+///
+/// This element is responsible for:
+/// - Attaching/detaching the [RenderVisibilityDetector] to the render tree
+/// - Clearing visibility callback references during unmounting to prevent memory leaks
+/// - Coordinating visibility updates with [VisibilityDetectorController]
+///
+/// When this element is unmounted from the widget tree, it will:
+/// 1. Nullify the [RenderVisibilityDetector.onVisibilityChanged] callback
+/// 2. Trigger disposal of the associated [RenderVisibilityDetector]
+/// 3. Release subscriptions to visibility tracking mechanisms
+///
+/// {@template visibility_detector_element_ownership}
+/// This element is automatically created and managed by the framework when using
+/// a [VisibilityDetector] widget. Developers should never need to instantiate this
+/// class directly.
+/// {@endtemplate}
+///
+/// See also:
+/// - [VisibilityDetector], the widget that creates this element
+/// - [RenderVisibilityDetector], the render object managed by this element
+class VisibilityDetectorElement extends SingleChildRenderObjectElement {
+  VisibilityDetectorElement(VisibilityDetector widget) : super(widget);
+
+  @override
+  void unmount() {
+    final renderObject = this.renderObject;
+    if (renderObject is RenderVisibilityDetector) {
+      renderObject.onVisibilityChanged = null;
+    }
+    super.unmount();
+  }
+}
+
+/// An [Element] that manages the lifecycle of the associated [RenderSliverVisibilityDetector].
+///
+/// This element is responsible for:
+/// - Attaching/detaching the [RenderSliverVisibilityDetector] to the render tree
+/// - Clearing visibility callback references during unmounting to prevent memory leaks
+/// - Coordinating visibility updates with [VisibilityDetectorController]
+///
+/// When this element is unmounted from the widget tree, it will:
+/// 1. Nullify the [RenderSliverVisibilityDetector.onVisibilityChanged] callback
+/// 2. Trigger disposal of the associated [RenderSliverVisibilityDetector]
+/// 3. Release subscriptions to visibility tracking mechanisms
+///
+/// {@template sliver_visibility_detector_element_ownership}
+/// This element is automatically created and managed by the framework when using
+/// a [SliverVisibilityDetector] widget. Developers should never need to instantiate this
+/// class directly.
+/// {@endtemplate}
+///
+/// See also:
+/// - [SliverVisibilityDetector], the widget that creates this element
+/// - [RenderSliverVisibilityDetector], the render object managed by this element
+class SliverVisibilityDetectorElement extends SingleChildRenderObjectElement {
+  SliverVisibilityDetectorElement(SliverVisibilityDetector widget)
+      : super(widget);
+
+  @override
+  void unmount() {
+    final renderObject = this.renderObject;
+    if (renderObject is RenderSliverVisibilityDetector) {
+      renderObject.onVisibilityChanged = null;
+    }
+    super.unmount();
+  }
+}

packages/visibility_detector/lib/visibility_detector.dart

@@ -6,3 +6,4 @@
 
 export 'src/visibility_detector.dart';
 export 'src/visibility_detector_controller.dart';
+export 'src/visibility_detector_element.dart';