fixes cupertino page transition leak

packages/flutter/lib/src/cupertino/route.dart

@@ -378,56 +378,105 @@ class CupertinoPage<T> extends Page<T> {
 ///
 /// The page slides in from the right and exits in reverse. It also shifts to the left in
 /// a parallax motion when another page enters to cover it.
-class CupertinoPageTransition extends StatelessWidget {
+class CupertinoPageTransition extends StatefulWidget {
   /// Creates an iOS-style page transition.
   ///
+  const CupertinoPageTransition({
+    super.key,
+    required this.primaryRouteAnimation,
+    required this.secondaryRouteAnimation,
+    required this.child,
+    required this.linearTransition,
+  });
+
+  /// The widget below this widget in the tree.
+  final Widget child;
+
   ///  * `primaryRouteAnimation` is a linear route animation from 0.0 to 1.0
   ///    when this screen is being pushed.
+  final Animation<double> primaryRouteAnimation;
+
   ///  * `secondaryRouteAnimation` is a linear route animation from 0.0 to 1.0
   ///    when another screen is being pushed on top of this one.
+  final Animation<double> secondaryRouteAnimation;
+
   ///  * `linearTransition` is whether to perform the transitions linearly.
   ///    Used to precisely track back gesture drags.
-  CupertinoPageTransition({
-    super.key,
-    required Animation<double> primaryRouteAnimation,
-    required Animation<double> secondaryRouteAnimation,
-    required this.child,
-    required bool linearTransition,
-  }) : _primaryPositionAnimation =
-           (linearTransition
-             ? primaryRouteAnimation
-             : CurvedAnimation(
-                 parent: primaryRouteAnimation,
+  final bool linearTransition;
+
+  @override
+  State<CupertinoPageTransition> createState() => _CupertinoPageTransitionState();
+}
+
+class _CupertinoPageTransitionState extends State<CupertinoPageTransition> {
+
+
+  // When this page is coming in to cover another page.
+  late Animation<Offset> _primaryPositionAnimation;
+  // When this page is becoming covered by another page.
+  late Animation<Offset> _secondaryPositionAnimation;
+  // Shadow of page which is coming in to cover another page.
+  late Animation<Decoration> _primaryShadowAnimation;
+  // Curve of primary page which is coming in to cover another page.
+  CurvedAnimation? _primaryPositionCurve;
+  // Curve of secondary page which is becoming covered by another page.
+  CurvedAnimation? _secondaryPositionCurve;
+  // Curve of primary page's shadow.
+  CurvedAnimation? _primaryShadowCurve;
+
+  @override
+  void initState() {
+    super.initState();
+    _init();
+  }
+
+  @override
+  void didUpdateWidget(covariant CupertinoPageTransition oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    _disposeCurve();
+    _init();
+  }
+
+  @override
+  void dispose() {
+    super.dispose();
+    _disposeCurve();
+  }
+
+  void _disposeCurve() {
+    _primaryPositionCurve?.dispose();
+    _secondaryPositionCurve?.dispose();
+    _primaryShadowCurve?.dispose();
+  }
+
+  void _init() {
+    _primaryPositionAnimation =
+           (widget.linearTransition
+             ? widget.primaryRouteAnimation
+             : _primaryPositionCurve = CurvedAnimation(
+                 parent: widget.primaryRouteAnimation,
                  curve: Curves.fastEaseInToSlowEaseOut,
                  reverseCurve: Curves.fastEaseInToSlowEaseOut.flipped,
                )
-           ).drive(_kRightMiddleTween),
+           ).drive(_kRightMiddleTween);
        _secondaryPositionAnimation =
-           (linearTransition
-             ? secondaryRouteAnimation
-             : CurvedAnimation(
-                 parent: secondaryRouteAnimation,
+           (widget.linearTransition
+             ? widget.secondaryRouteAnimation
+             : _secondaryPositionCurve = CurvedAnimation(
+                 parent: widget.secondaryRouteAnimation,
                  curve: Curves.linearToEaseOut,
                  reverseCurve: Curves.easeInToLinear,
                )
-           ).drive(_kMiddleLeftTween),
+           ).drive(_kMiddleLeftTween);
        _primaryShadowAnimation =
-           (linearTransition
-             ? primaryRouteAnimation
-             : CurvedAnimation(
-                 parent: primaryRouteAnimation,
+           (widget.linearTransition
+             ? widget.primaryRouteAnimation
+             : _secondaryPositionCurve = CurvedAnimation(
+                 parent: widget.primaryRouteAnimation,
                  curve: Curves.linearToEaseOut,
                )
            ).drive(_CupertinoEdgeShadowDecoration.kTween);
-
-  // When this page is coming in to cover another page.
-  final Animation<Offset> _primaryPositionAnimation;
-  // When this page is becoming covered by another page.
-  final Animation<Offset> _secondaryPositionAnimation;
-  final Animation<Decoration> _primaryShadowAnimation;
-
-  /// The widget below this widget in the tree.
-  final Widget child;
+  }
 
   @override
   Widget build(BuildContext context) {
@@ -442,7 +491,7 @@ class CupertinoPageTransition extends StatelessWidget {
         textDirection: textDirection,
         child: DecoratedBoxTransition(
           decoration: _primaryShadowAnimation,
-          child: child,
+          child: widget.child,
         ),
       ),
     );