fix a bug when android uses CupertinoPageTransitionsBuilder... (#114303)

When android uses iOS style `PageTransitionsBuilder` and iOS uses android style `PageTransitionsBuilder`, on android, swipe from the left edge of the screen doesn't work. This PR solves that problem.

#99919 introduced a breaking change, the pr re-implemented it <del>without introducing a breaking change.**</del>

packages/flutter/lib/src/material/page.dart

@@ -80,6 +80,8 @@ class MaterialPageRoute<T> extends PageRoute<T> with MaterialRouteTransitionMixi
 ///  * [CupertinoPageTransitionsBuilder], which is the default page transition
 ///    for iOS and macOS.
 mixin MaterialRouteTransitionMixin<T> on PageRoute<T> {
+  TargetPlatform? _effectiveTargetPlatform;
+
   /// Builds the primary contents of the route.
   @protected
   Widget buildContent(BuildContext context);
@@ -116,8 +118,20 @@ mixin MaterialRouteTransitionMixin<T> on PageRoute<T> {
 
   @override
   Widget buildTransitions(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
-    final PageTransitionsTheme theme = Theme.of(context).pageTransitionsTheme;
-    return theme.buildTransitions<T>(this, context, animation, secondaryAnimation, child);
+    return ValueListenableBuilder<bool>(
+      valueListenable: navigator!.userGestureInProgressNotifier,
+      builder: (BuildContext context, bool useGestureInProgress, Widget? _) {
+        final ThemeData themeData = Theme.of(context);
+
+        if (useGestureInProgress) {
+          // The platform should be kept unchanged during an user gesture.
+          _effectiveTargetPlatform ??= themeData.platform;
+        } else {
+          _effectiveTargetPlatform = themeData.platform;
+        }
+        return themeData.pageTransitionsTheme.buildTransitions<T>(this, context, animation, secondaryAnimation, child, _effectiveTargetPlatform!);
+      },
+    );
   }
 }
 

packages/flutter/lib/src/material/page_transitions_theme.dart

@@ -741,7 +741,7 @@ class PageTransitionsTheme with Diagnosticable {
   Map<TargetPlatform, PageTransitionsBuilder> get builders => _builders;
   final Map<TargetPlatform, PageTransitionsBuilder> _builders;
 
-  /// Delegates to the builder for the current [ThemeData.platform].
+  /// Delegates to the builder for the current [platform].
   /// If a builder for the current platform is not found, then the
   /// [ZoomPageTransitionsBuilder] is used.
   ///
@@ -752,13 +752,8 @@ class PageTransitionsTheme with Diagnosticable {
     Animation<double> animation,
     Animation<double> secondaryAnimation,
     Widget child,
+    TargetPlatform platform,
   ) {
-    TargetPlatform platform = Theme.of(context).platform;
-
-    if (CupertinoRouteTransitionMixin.isPopGestureInProgress(route)) {
-      platform = TargetPlatform.iOS;
-    }
-
     final PageTransitionsBuilder matchingBuilder =
       builders[platform] ?? const ZoomPageTransitionsBuilder();
     return matchingBuilder.buildTransitions<T>(route, context, animation, secondaryAnimation, child);

packages/flutter/test/material/page_transitions_theme_test.dart

@@ -350,4 +350,140 @@ void main() {
     await tester.pumpAndSettle();
     expect(builtCount, 1);
   }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+
+  testWidgets('android can use CupertinoPageTransitionsBuilder', (WidgetTester tester) async {
+    int builtCount = 0;
+
+    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
+      '/': (BuildContext context) => Material(
+        child: TextButton(
+          child: const Text('push'),
+          onPressed: () { Navigator.of(context).pushNamed('/b'); },
+        ),
+      ),
+      '/b': (BuildContext context) => StatefulBuilder(
+        builder: (BuildContext context, StateSetter setState) {
+          builtCount++;
+          return TextButton(
+            child: const Text('pop'),
+            onPressed: () { Navigator.pop(context); },
+          );
+        },
+      ),
+    };
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          pageTransitionsTheme: const PageTransitionsTheme(
+            builders: <TargetPlatform, PageTransitionsBuilder>{
+              TargetPlatform.android: CupertinoPageTransitionsBuilder(),
+              // iOS uses different PageTransitionsBuilder
+              TargetPlatform.iOS: FadeUpwardsPageTransitionsBuilder(),
+            },
+          ),
+        ),
+        routes: routes,
+      ),
+    );
+
+    // No matter push or pop was called, the child widget should built only once.
+    await tester.tap(find.text('push'));
+    await tester.pumpAndSettle();
+    expect(builtCount, 1);
+
+    final Size size = tester.getSize(find.byType(MaterialApp));
+    await tester.flingFrom(Offset(0, size.height / 2), Offset(size.width * 2 / 3, 0), 500);
+
+    await tester.pumpAndSettle();
+    expect(find.text('push'), findsOneWidget);
+    expect(builtCount, 1);
+  }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+
+  testWidgets('back gesture while TargetPlatform changes', (WidgetTester tester) async {
+    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
+      '/': (BuildContext context) => Material(
+        child: TextButton(
+          child: const Text('PUSH'),
+          onPressed: () { Navigator.of(context).pushNamed('/b'); },
+        ),
+      ),
+      '/b': (BuildContext context) => const Text('HELLO'),
+    };
+    const PageTransitionsTheme pageTransitionsTheme = PageTransitionsTheme(
+      builders: <TargetPlatform, PageTransitionsBuilder>{
+        TargetPlatform.android: CupertinoPageTransitionsBuilder(),
+        // iOS uses different PageTransitionsBuilder
+        TargetPlatform.iOS: FadeUpwardsPageTransitionsBuilder(),
+      },
+    );
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          platform: TargetPlatform.android,
+          pageTransitionsTheme: pageTransitionsTheme,
+        ),
+        routes: routes,
+      ),
+    );
+    await tester.tap(find.text('PUSH'));
+    expect(await tester.pumpAndSettle(const Duration(minutes: 1)), 2);
+    expect(find.text('PUSH'), findsNothing);
+    expect(find.text('HELLO'), findsOneWidget);
+
+    final Offset helloPosition1 = tester.getCenter(find.text('HELLO'));
+    final TestGesture gesture = await tester.startGesture(const Offset(2.5, 300.0));
+    await tester.pump(const Duration(milliseconds: 20));
+    await gesture.moveBy(const Offset(100.0, 0.0));
+    expect(find.text('PUSH'), findsNothing);
+    expect(find.text('HELLO'), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 20));
+    expect(find.text('PUSH'), findsOneWidget);
+    expect(find.text('HELLO'), findsOneWidget);
+    final Offset helloPosition2 = tester.getCenter(find.text('HELLO'));
+    expect(helloPosition1.dx, lessThan(helloPosition2.dx));
+    expect(helloPosition1.dy, helloPosition2.dy);
+    expect(Theme.of(tester.element(find.text('HELLO'))).platform, TargetPlatform.android);
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          platform: TargetPlatform.iOS,
+          pageTransitionsTheme: pageTransitionsTheme,
+        ),
+        routes: routes,
+      ),
+    );
+    // Now, let the theme animation run through.
+    // This takes three frames (including the first one above):
+    //  1. Start the Theme animation. It's at t=0 so everything else is identical.
+    //  2. Start any animations that are informed by the Theme, for example, the
+    //     DefaultTextStyle, on the first frame that the theme is not at t=0. In
+    //     this case, it's at t=1.0 of the theme animation, so this is also the
+    //     frame in which the theme animation ends.
+    //  3. End all the other animations.
+    expect(await tester.pumpAndSettle(const Duration(minutes: 1)), 2);
+    expect(Theme.of(tester.element(find.text('HELLO'))).platform, TargetPlatform.iOS);
+    final Offset helloPosition3 = tester.getCenter(find.text('HELLO'));
+    expect(helloPosition3, helloPosition2);
+    expect(find.text('PUSH'), findsOneWidget);
+    expect(find.text('HELLO'), findsOneWidget);
+    await gesture.moveBy(const Offset(100.0, 0.0));
+    await tester.pump(const Duration(milliseconds: 20));
+    expect(find.text('PUSH'), findsOneWidget);
+    expect(find.text('HELLO'), findsOneWidget);
+    final Offset helloPosition4 = tester.getCenter(find.text('HELLO'));
+    expect(helloPosition3.dx, lessThan(helloPosition4.dx));
+    expect(helloPosition3.dy, helloPosition4.dy);
+    await gesture.moveBy(const Offset(500.0, 0.0));
+    await gesture.up();
+    expect(await tester.pumpAndSettle(const Duration(minutes: 1)), 3);
+    expect(find.text('PUSH'), findsOneWidget);
+    expect(find.text('HELLO'), findsNothing);
+
+    await tester.tap(find.text('PUSH'));
+    expect(await tester.pumpAndSettle(const Duration(minutes: 1)), 2);
+    expect(find.text('PUSH'), findsNothing);
+    expect(find.text('HELLO'), findsOneWidget);
+  });
 }