fix(1181): Navigator2 - Navigation animation glitches on back gesture (Android only)

lib/src/router/stacked_page.dart

@@ -23,6 +23,11 @@ abstract class StackedPage<T> extends Page<T> {
 
   Widget get child => _child;
 
+  // Track current route and listener state to prevent double-completion
+  // Navigator 2.0 can call createRoute() multiple times on the same Page instance
+  Route<T>? _currentRoute;
+  bool _hasAttachedListener = false;
+
   StackedPage({
     required this.routeData,
     required Widget child,
@@ -60,10 +65,20 @@ abstract class StackedPage<T> extends Page<T> {
 
   @override
   Route<T> createRoute(BuildContext context) {
-    return onCreateRoute(context)
-      ..popped.then(
-        _popCompleter.complete,
-      );
+    // Clear previous route reference to allow garbage collection
+    _currentRoute = null;
+
+    // Create the new route
+    _currentRoute = onCreateRoute(context);
+
+    // Only attach listener once to prevent "Future already completed" error
+    // Navigator 2.0 can call createRoute() multiple times during back gestures
+    if (!_hasAttachedListener) {
+      _currentRoute!.popped.then(_popCompleter.complete);
+      _hasAttachedListener = true;
+    }
+
+    return _currentRoute!;
   }
 }
 

lib/src/router/widgets/route_navigator.dart

@@ -71,12 +71,26 @@ class RouteNavigatorState extends State<RouteNavigator> {
             restorationScopeId:
                 widget.navRestorationScopeId ?? widget.router.routeData.name,
             pages: widget.router.stack,
-            onDidRemovePage: (page) {
-              if (page is StackedPage) {
-                var routeData = page.routeData;
-                widget.router.removeRoute(routeData);
-                widget.didPop?.call(routeData.route, null);
+            // ignore: deprecated_member_use
+            onPopPage: (route, result) {
+              // CRITICAL: Using deprecated onPopPage instead of onDidRemovePage
+              // because we MUST update router state BEFORE the pop completes.
+              // This is essential for Android predictive back gestures to work
+              // without animation glitches (double animations or forward replays).
+              // onDidRemovePage is called too late (after page removal) and causes
+              // page list mismatch during the animation, triggering visual glitches.
+              // See: https://github.com/flutter/flutter/issues/new (migration path unclear)
+              if (!route.didPop(result)) {
+                return false;
               }
+
+              if (route.settings is StackedPage) {
+                var page = route.settings as StackedPage;
+                widget.router.removeRoute(page.routeData);
+                widget.didPop?.call(page.routeData.route, result);
+              }
+
+              return true;
             },
           )
         : widget.placeholder?.call(context) ??