Page-subclasses to take children instead of builder (#66694)

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

@@ -93,7 +93,8 @@ final DecorationTween _kGradientShadowTween = DecorationTween(
 ///  * [CupertinoPageRoute], which is a [PageRoute] that leverages this mixin.
 mixin CupertinoRouteTransitionMixin<T> on PageRoute<T> {
   /// Builds the primary contents of the route.
-  WidgetBuilder get builder;
+  @protected
+  Widget buildContent(BuildContext context);
 
   /// {@template flutter.cupertino.cupertinoRouteTransitionMixin.title}
   /// A title string for this route.
@@ -224,7 +225,7 @@ mixin CupertinoRouteTransitionMixin<T> on PageRoute<T> {
 
   @override
   Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-    final Widget child = builder(context);
+    final Widget child = buildContent(context);
     final Widget result = Semantics(
       scopesRoute: true,
       explicitChildNodes: true,
@@ -351,9 +352,12 @@ class CupertinoPageRoute<T> extends PageRoute<T> with CupertinoRouteTransitionMi
        assert(opaque),
        super(settings: settings, fullscreenDialog: fullscreenDialog);
 
-  @override
+  /// Builds the primary contents of the route.
   final WidgetBuilder builder;
 
+  @override
+  Widget buildContent(BuildContext context) => builder(context);
+
   @override
   final String? title;
 
@@ -378,7 +382,7 @@ class _PageBasedCupertinoPageRoute<T> extends PageRoute<T> with CupertinoRouteTr
   CupertinoPage<T> get _page => settings as CupertinoPage<T>;
 
   @override
-  WidgetBuilder get builder => _page.builder;
+  Widget buildContent(BuildContext context) => _page.child;
 
   @override
   String? get title => _page.title;
@@ -412,20 +416,20 @@ class _PageBasedCupertinoPageRoute<T> extends PageRoute<T> with CupertinoRouteTr
 class CupertinoPage<T> extends Page<T> {
   /// Creates a cupertino page.
   const CupertinoPage({
-    required this.builder,
+    required this.child,
     this.maintainState = true,
     this.title,
     this.fullscreenDialog = false,
     LocalKey? key,
     String? name,
     Object? arguments,
-  }) : assert(builder != null),
+  }) : assert(child != null),
        assert(maintainState != null),
        assert(fullscreenDialog != null),
        super(key: key, name: name, arguments: arguments);
 
-  /// Builds the primary contents of the route.
-  final WidgetBuilder builder;
+  /// The content to be shown in the [Route] created by this page.
+  final Widget child;
 
   /// {@macro flutter.cupertino.cupertinoRouteTransitionMixin.title}
   final String? title;

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

@@ -48,9 +48,12 @@ class MaterialPageRoute<T> extends PageRoute<T> with MaterialRouteTransitionMixi
        assert(opaque),
        super(settings: settings, fullscreenDialog: fullscreenDialog);
 
-  @override
+  /// Builds the primary contents of the route.
   final WidgetBuilder builder;
 
+  @override
+  Widget buildContent(BuildContext context) => builder(context);
+
   @override
   final bool maintainState;
 
@@ -77,7 +80,8 @@ class MaterialPageRoute<T> extends PageRoute<T> with MaterialRouteTransitionMixi
 ///    by the [MaterialRouteTransitionMixin.buildTransitions].
 mixin MaterialRouteTransitionMixin<T> on PageRoute<T> {
   /// Builds the primary contents of the route.
-  WidgetBuilder get builder;
+  @protected
+  Widget buildContent(BuildContext context);
 
   @override
   Duration get transitionDuration => const Duration(milliseconds: 300);
@@ -101,7 +105,7 @@ mixin MaterialRouteTransitionMixin<T> on PageRoute<T> {
     Animation<double> animation,
     Animation<double> secondaryAnimation,
   ) {
-    final Widget result = builder(context);
+    final Widget result = buildContent(context);
     assert(() {
       if (result == null) {
         throw FlutterError(
@@ -148,19 +152,19 @@ mixin MaterialRouteTransitionMixin<T> on PageRoute<T> {
 class MaterialPage<T> extends Page<T> {
   /// Creates a material page.
   const MaterialPage({
-    @required this.builder,
+    @required this.child,
     this.maintainState = true,
     this.fullscreenDialog = false,
     LocalKey key,
     String name,
     Object arguments,
-  }) : assert(builder != null),
+  }) : assert(child != null),
        assert(maintainState != null),
        assert(fullscreenDialog != null),
        super(key: key, name: name, arguments: arguments);
 
-  /// Builds the primary contents of the route.
-  final WidgetBuilder builder;
+  /// The content to be shown in the [Route] created by this page.
+  final Widget child;
 
   /// {@macro flutter.widgets.modalRoute.maintainState}
   final bool maintainState;
@@ -188,7 +192,9 @@ class _PageBasedMaterialPageRoute<T> extends PageRoute<T> with MaterialRouteTran
   MaterialPage<T> get _page => settings as MaterialPage<T>;
 
   @override
-  WidgetBuilder get builder => _page.builder;
+  Widget buildContent(BuildContext context) {
+    return _page.child;
+  }
 
   @override
   bool get maintainState => _page.maintainState;

packages/flutter/lib/src/widgets/navigator.dart

@@ -37,11 +37,6 @@ import 'ticker_provider.dart';
 ///  * [Navigator], which is where all the [Route]s end up.
 typedef RouteFactory = Route<dynamic>? Function(RouteSettings settings);
 
-/// Creates a route for the given context and route settings.
-///
-/// Used by [CustomBuilderPage.routeBuilder].
-typedef RouteBuilder<T> = Route<T> Function(BuildContext context, RouteSettings settings);
-
 /// Creates a series of one or more routes.
 ///
 /// Used by [Navigator.onGenerateInitialRoutes].
@@ -507,8 +502,6 @@ class RouteSettings {
 ///
 ///  * [Navigator.pages], which accepts a list of [Page]s and updates its routes
 ///    history.
-///  * [CustomBuilderPage], a [Page] subclass that provides the API to build a
-///    customized route.
 abstract class Page<T> extends RouteSettings {
   /// Creates a page and initializes [key] for subclasses.
   ///
@@ -543,38 +536,6 @@ abstract class Page<T> extends RouteSettings {
   String toString() => '${objectRuntimeType(this, 'Page')}("$name", $key, $arguments)';
 }
 
-/// A [Page] that builds a customized [Route] based on the [routeBuilder].
-///
-/// The type argument `T` is the corresponding [Route]'s return type, as
-/// used by [Route.currentResult], [Route.popped], and [Route.didPop].
-class CustomBuilderPage<T> extends Page<T> {
-  /// Creates a page with a custom route builder.
-  ///
-  /// Use [routeBuilder] to specify the route that will be created from this
-  /// page.
-  const CustomBuilderPage({
-    required LocalKey key,
-    required this.routeBuilder,
-    String? name,
-    Object? arguments,
-  }) : assert(key != null),
-       assert(routeBuilder != null),
-       super(key: key, name: name, arguments: arguments);
-
-  /// A builder that will be called during [createRoute] to create a [Route].
-  ///
-  /// The routes returned from this builder must have their settings equal to
-  /// the input `settings`.
-  final RouteBuilder<T> routeBuilder;
-
-  @override
-  Route<T> createRoute(BuildContext context) {
-    final Route<T> route = routeBuilder(context, this);
-    assert(route.settings == this);
-    return route;
-  }
-}
-
 /// An interface for observing the behavior of a [Navigator].
 class NavigatorObserver {
   /// The navigator that the observer is observing, if any.
@@ -1045,10 +1006,10 @@ class DefaultTransitionDelegate<T> extends TransitionDelegate<T> {
 /// The [Navigator] will convert its [Navigator.pages] into a stack of [Route]s
 /// if it is provided. A change in [Navigator.pages] will trigger an update to
 /// the stack of [Route]s. The [Navigator] will update its routes to match the
-/// new configuration of its [Navigator.pages]. To use this API, one can use
-/// [CustomBuilderPage] or create a [Page] subclass and defines a list of
-/// [Page]s for [Navigator.pages]. A [Navigator.onPopPage] callback is also
-/// required to properly clean up the input pages in case of a pop.
+/// new configuration of its [Navigator.pages]. To use this API, one can create
+/// a [Page] subclass and defines a list of [Page]s for [Navigator.pages]. A
+/// [Navigator.onPopPage] callback is also required to properly clean up the
+/// input pages in case of a pop.
 ///
 /// By Default, the [Navigator] will use [DefaultTransitionDelegate] to decide
 /// how routes transition in or out of the screen. To customize it, define a

packages/flutter/lib/src/widgets/pages.dart

@@ -46,10 +46,6 @@ Widget _defaultTransitionsBuilder(BuildContext context, Animation<double> animat
 ///
 /// Callers must define the [pageBuilder] function which creates the route's
 /// primary contents. To add transitions define the [transitionsBuilder] function.
-///
-/// See also:
-///
-///  * [TransitionBuilderPage], which is a [Page] of this class.
 class PageRouteBuilder<T> extends PageRoute<T> {
   /// Creates a route that delegates to builder callbacks.
   ///
@@ -120,126 +116,3 @@ class PageRouteBuilder<T> extends PageRoute<T> {
     return transitionsBuilder(context, animation, secondaryAnimation, child);
   }
 }
-
-/// A page that creates a [PageRoute] with customizable transition.
-///
-/// Similar to the [PageRouteBuilder], callers must define the [pageBuilder]
-/// function which creates the route's primary contents. To add transitions
-/// define the [transitionsBuilder] function.
-///
-/// See also:
-///
-///  * [PageRouteBuilder], which is a [PageRoute] version of this class.
-class TransitionBuilderPage<T> extends Page<T> {
-  /// Creates a [TransitionBuilderPage].
-  const TransitionBuilderPage({
-    required this.pageBuilder,
-    this.transitionsBuilder = _defaultTransitionsBuilder,
-    this.transitionDuration = const Duration(milliseconds: 300),
-    this.reverseTransitionDuration = const Duration(milliseconds: 300),
-    this.opaque = true,
-    this.barrierDismissible = false,
-    this.barrierColor,
-    this.barrierLabel,
-    this.maintainState = true,
-    this.fullscreenDialog = false,
-    LocalKey? key,
-    String? name,
-    Object? arguments,
-  }) : assert(pageBuilder != null),
-       assert(transitionsBuilder != null),
-       assert(opaque != null),
-       assert(barrierDismissible != null),
-       assert(maintainState != null),
-       assert(fullscreenDialog != null),
-       super(key: key, name: name, arguments: arguments);
-
-  /// {@macro flutter.widgets.pageRouteBuilder.pageBuilder}
-  final RoutePageBuilder pageBuilder;
-
-  /// {@macro flutter.widgets.pageRouteBuilder.transitionsBuilder}
-  final RouteTransitionsBuilder transitionsBuilder;
-
-  /// {@macro flutter.widgets.transitionRoute.transitionDuration}
-  final Duration transitionDuration;
-
-  /// {@macro flutter.widgets.transitionRoute.reverseTransitionDuration}
-  final Duration reverseTransitionDuration;
-
-  /// {@macro flutter.widgets.transitionRoute.opaque}
-  final bool opaque;
-
-  /// {@macro flutter.widgets.modalRoute.barrierDismissible}
-  final bool barrierDismissible;
-
-  /// {@macro flutter.widgets.modalRoute.barrierColor}
-  ///
-  /// See also:
-  ///
-  ///  * [barrierDismissible], which controls the behavior of the barrier when
-  ///    tapped.
-  ///  * [ModalBarrier], the widget that implements this feature.
-  final Color? barrierColor;
-
-  /// {@macro flutter.widgets.modalRoute.barrierLabel}
-  ///
-  /// See also:
-  ///
-  ///  * [barrierDismissible], which controls the behavior of the barrier when
-  ///    tapped.
-  ///  * [ModalBarrier], the widget that implements this feature.
-  final String? barrierLabel;
-
-  /// {@macro flutter.widgets.modalRoute.maintainState}
-  final bool maintainState;
-
-  /// {@macro flutter.widgets.pageRoute.fullscreenDialog}
-  final bool fullscreenDialog;
-
-  @override
-  Route<T> createRoute(BuildContext context) => _PageBasedPageRouteBuilder<T>(this);
-}
-
-// A page-based version of the [PageRouteBuilder].
-//
-// This class gets its builder and settings directly from the [TransitionBuilderPage],
-// so that its content updates accordingly to the [TransitionBuilderPage].
-class _PageBasedPageRouteBuilder<T> extends PageRoute<T>{
-  _PageBasedPageRouteBuilder(
-    TransitionBuilderPage<T> page,
-  ) : assert(page != null),
-       super(settings: page, fullscreenDialog: page.fullscreenDialog);
-
-  TransitionBuilderPage<T> get _page => settings as TransitionBuilderPage<T>;
-
-  @override
-  Duration get transitionDuration => _page.transitionDuration;
-
-  @override
-  Duration get reverseTransitionDuration => _page.reverseTransitionDuration;
-
-  @override
-  bool get opaque => _page.opaque;
-
-  @override
-  bool get barrierDismissible => _page.barrierDismissible;
-
-  @override
-  Color? get barrierColor => _page.barrierColor;
-
-  @override
-  String? get barrierLabel => _page.barrierLabel;
-
-  @override
-  bool get maintainState => _page.maintainState;
-
-  @override
-  Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-    return _page.pageBuilder(context, animation, secondaryAnimation);
-  }
-
-  @override
-  Widget buildTransitions(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
-    return _page.transitionsBuilder(context, animation, secondaryAnimation, child);
-  }
-}

packages/flutter/test/cupertino/app_test.dart

@@ -236,12 +236,12 @@ class SimpleNavigatorRouterDelegate extends RouterDelegate<RouteInformation> wit
       pages: <Page<void>>[
         // We need at least two pages for the pop to propagate through.
         // Otherwise, the navigator will bubble the pop to the system navigator.
-        CupertinoPage<void>(
-          builder: (BuildContext context) => const Text('base'),
+        const CupertinoPage<void>(
+          child:  Text('base'),
         ),
         CupertinoPage<void>(
           key: ValueKey<String>(routeInformation?.location),
-          builder: (BuildContext context) => builder(context, routeInformation),
+          child: builder(context, routeInformation),
         )
       ],
     );

packages/flutter/test/cupertino/page_test.dart

@@ -464,6 +464,19 @@ void main() {
     expect(find.text('Page 1'), findsNothing);
     expect(find.text('Page 2'), isOnstage);
   });
+
+  testWidgets('CupertinoPage does not lose its state when transitioning out', (WidgetTester tester) async {
+    final GlobalKey<NavigatorState> navigator = GlobalKey<NavigatorState>();
+    await tester.pumpWidget(KeepsStateTestWidget(navigatorKey: navigator));
+    expect(find.text('subpage'), findsOneWidget);
+    expect(find.text('home'), findsNothing);
+
+    navigator.currentState.pop();
+    await tester.pump();
+
+    expect(find.text('subpage'), findsOneWidget);
+    expect(find.text('home'), findsOneWidget);
+  });
 }
 
 class RtlOverrideWidgetsDelegate extends LocalizationsDelegate<WidgetsLocalizations> {
@@ -481,3 +494,38 @@ class RtlOverrideWidgetsLocalization implements WidgetsLocalizations {
   @override
   TextDirection get textDirection => TextDirection.rtl;
 }
+
+class KeepsStateTestWidget extends StatefulWidget {
+  const KeepsStateTestWidget({this.navigatorKey});
+
+  final Key navigatorKey;
+
+  @override
+  State<KeepsStateTestWidget> createState() => _KeepsStateTestWidgetState();
+}
+
+class _KeepsStateTestWidgetState extends State<KeepsStateTestWidget> {
+  String _subpage = 'subpage';
+
+  @override
+  Widget build(BuildContext context) {
+    return CupertinoApp(
+      home: Navigator(
+        key: widget.navigatorKey,
+        pages: <Page<void>>[
+          const CupertinoPage<void>(child: Text('home')),
+          if (_subpage != null) CupertinoPage<void>(child: Text(_subpage)),
+        ],
+        onPopPage: (Route<dynamic> route, dynamic result) {
+          if (!route.didPop(result)) {
+            return false;
+          }
+          setState(() {
+            _subpage = null;
+          });
+          return true;
+        },
+      ),
+    );
+  }
+}

packages/flutter/test/cupertino/route_test.dart

@@ -1382,12 +1382,10 @@ void main() {
       CupertinoPage<void>(
         key: pageKey,
         title: 'title one',
-        builder: (BuildContext context) {
-          return CupertinoPageScaffold(
-            navigationBar: CupertinoNavigationBar(key: UniqueKey()),
-            child: const Text('first'),
-          );
-        }
+        child: CupertinoPageScaffold(
+          navigationBar: CupertinoNavigationBar(key: UniqueKey()),
+          child: const Text('first'),
+        ),
       ),
     ];
     await tester.pumpWidget(
@@ -1406,12 +1404,10 @@ void main() {
       CupertinoPage<void>(
         key: pageKey,
         title: 'title two',
-        builder: (BuildContext context) {
-          return CupertinoPageScaffold(
-            navigationBar: CupertinoNavigationBar(key: UniqueKey()),
-            child: const Text('second'),
-          );
-        }
+        child: CupertinoPageScaffold(
+          navigationBar: CupertinoNavigationBar(key: UniqueKey()),
+          child: const Text('second'),
+        ),
       ),
     ];
 
@@ -1437,8 +1433,8 @@ void main() {
     final LocalKey pageKeyTwo = UniqueKey();
     final TransitionDetector detector = TransitionDetector();
     List<Page<void>> myPages = <Page<void>>[
-      CupertinoPage<void>(key: pageKeyOne, maintainState: false, builder: (BuildContext context) => const Text('first')),
-      CupertinoPage<void>(key: pageKeyTwo, builder: (BuildContext context) => const Text('second')),
+      CupertinoPage<void>(key: pageKeyOne, maintainState: false, child: const Text('first')),
+      CupertinoPage<void>(key: pageKeyTwo, child: const Text('second')),
     ];
     await tester.pumpWidget(
       buildNavigator(
@@ -1454,8 +1450,8 @@ void main() {
     expect(find.text('second'), findsOneWidget);
 
     myPages = <Page<void>>[
-      CupertinoPage<void>(key: pageKeyOne, maintainState: true, builder: (BuildContext context) => const Text('first')),
-      CupertinoPage<void>(key: pageKeyTwo, builder: (BuildContext context) => const Text('second')),
+      CupertinoPage<void>(key: pageKeyOne, maintainState: true, child: const Text('first')),
+      CupertinoPage<void>(key: pageKeyTwo, child: const Text('second')),
     ];
 
     await tester.pumpWidget(

packages/flutter/test/material/app_test.dart

@@ -1056,12 +1056,12 @@ class SimpleNavigatorRouterDelegate extends RouterDelegate<RouteInformation> wit
       pages: <Page<void>>[
         // We need at least two pages for the pop to propagate through.
         // Otherwise, the navigator will bubble the pop to the system navigator.
-        MaterialPage<void>(
-          builder: (BuildContext context) => const Text('base'),
+        const MaterialPage<void>(
+          child: Text('base'),
         ),
         MaterialPage<void>(
           key: ValueKey<String>(routeInformation?.location),
-          builder: (BuildContext context) => builder(context, routeInformation),
+          child: builder(context, routeInformation),
         )
       ],
     );

packages/flutter/test/material/page_test.dart

@@ -841,7 +841,7 @@ void main() {
     final LocalKey pageKey = UniqueKey();
     final TransitionDetector detector = TransitionDetector();
     List<Page<void>> myPages = <Page<void>>[
-      MaterialPage<void>(key: pageKey, builder: (BuildContext context) => const Text('first')),
+      MaterialPage<void>(key: pageKey, child: const Text('first')),
     ];
     await tester.pumpWidget(
       buildNavigator(
@@ -855,7 +855,7 @@ void main() {
     expect(find.text('first'), findsOneWidget);
 
     myPages = <Page<void>>[
-      MaterialPage<void>(key: pageKey, builder: (BuildContext context) => const Text('second')),
+      MaterialPage<void>(key: pageKey, child: const Text('second')),
     ];
 
     await tester.pumpWidget(
@@ -877,8 +877,8 @@ void main() {
     final LocalKey pageKeyTwo = UniqueKey();
     final TransitionDetector detector = TransitionDetector();
     List<Page<void>> myPages = <Page<void>>[
-      MaterialPage<void>(key: pageKeyOne, maintainState: false, builder: (BuildContext context) => const Text('first')),
-      MaterialPage<void>(key: pageKeyTwo, builder: (BuildContext context) => const Text('second')),
+      MaterialPage<void>(key: pageKeyOne, maintainState: false, child: const Text('first')),
+      MaterialPage<void>(key: pageKeyTwo, child: const Text('second')),
     ];
     await tester.pumpWidget(
       buildNavigator(
@@ -894,8 +894,8 @@ void main() {
     expect(find.text('second'), findsOneWidget);
 
     myPages = <Page<void>>[
-      MaterialPage<void>(key: pageKeyOne, maintainState: true, builder: (BuildContext context) => const Text('first')),
-      MaterialPage<void>(key: pageKeyTwo, builder: (BuildContext context) => const Text('second')),
+      MaterialPage<void>(key: pageKeyOne, maintainState: true, child: const Text('first')),
+      MaterialPage<void>(key: pageKeyTwo, child: const Text('second')),
     ];
 
     await tester.pumpWidget(
@@ -912,6 +912,19 @@ void main() {
     expect(find.text('first', skipOffstage: false), findsOneWidget);
     expect(find.text('second'), findsOneWidget);
   });
+
+  testWidgets('MaterialPage does not lose its state when transitioning out', (WidgetTester tester) async {
+    final GlobalKey<NavigatorState> navigator = GlobalKey<NavigatorState>();
+    await tester.pumpWidget(KeepsStateTestWidget(navigatorKey: navigator));
+    expect(find.text('subpage'), findsOneWidget);
+    expect(find.text('home'), findsNothing);
+
+    navigator.currentState.pop();
+    await tester.pump();
+
+    expect(find.text('subpage'), findsOneWidget);
+    expect(find.text('home'), findsOneWidget);
+  });
 }
 
 class TransitionDetector extends DefaultTransitionDelegate<void> {
@@ -957,3 +970,38 @@ Widget buildNavigator({
     ),
   );
 }
+
+class KeepsStateTestWidget extends StatefulWidget {
+  const KeepsStateTestWidget({this.navigatorKey});
+
+  final Key navigatorKey;
+
+  @override
+  State<KeepsStateTestWidget> createState() => _KeepsStateTestWidgetState();
+}
+
+class _KeepsStateTestWidgetState extends State<KeepsStateTestWidget> {
+  String _subpage = 'subpage';
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: Navigator(
+        key: widget.navigatorKey,
+        pages: <Page<void>>[
+          const MaterialPage<void>(child: Text('home')),
+          if (_subpage != null) MaterialPage<void>(child: Text(_subpage)),
+        ],
+        onPopPage: (Route<dynamic> route, dynamic result) {
+          if (!route.didPop(result)) {
+            return false;
+          }
+          setState(() {
+            _subpage = null;
+          });
+          return true;
+        },
+      ),
+    );
+  }
+}

packages/flutter/test/widgets/app_test.dart

@@ -366,12 +366,12 @@ class SimpleNavigatorRouterDelegate extends RouterDelegate<RouteInformation> wit
       pages: <Page<void>>[
         // We need at least two pages for the pop to propagate through.
         // Otherwise, the navigator will bubble the pop to the system navigator.
-        MaterialPage<void>(
-          builder: (BuildContext context) => const Text('base'),
+        const MaterialPage<void>(
+          child: Text('base'),
         ),
         MaterialPage<void>(
           key: ValueKey<String>(routeInformation?.location),
-          builder: (BuildContext context) => builder(context, routeInformation),
+          child: builder(context, routeInformation),
         )
       ],
     );

packages/flutter/test/widgets/route_notification_messages_test.dart

@@ -119,11 +119,8 @@ void main() {
     await tester.pumpWidget(Directionality(
       textDirection: TextDirection.ltr,
       child: Navigator(
-        pages: <Page<void>>[
-          TransitionBuilderPage<void>(
-            name: '/',
-            pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) => const Placeholder(),
-          ),
+        pages: const <Page<void>>[
+          TestPage(name: '/'),
         ],
         onPopPage: (Route<void> route, void result) => false,
       )
@@ -134,15 +131,9 @@ void main() {
     await tester.pumpWidget(Directionality(
       textDirection: TextDirection.ltr,
       child: Navigator(
-        pages: <Page<void>>[
-          TransitionBuilderPage<void>(
-            name: '/',
-            pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) => const Placeholder(),
-          ),
-          TransitionBuilderPage<void>(
-            name: '/abc',
-            pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) => const Placeholder(),
-          ),
+        pages: const <Page<void>>[
+          TestPage(name: '/'),
+          TestPage(name: '/abc',),
         ],
         onPopPage: (Route<void> route, void result) => false,
       )
@@ -371,3 +362,15 @@ class SimpleRouterDelegate extends RouterDelegate<RouteInformation> with ChangeN
   @override
   Widget build(BuildContext context) => builder(context, routeInformation);
 }
+
+class TestPage extends Page<void> {
+  const TestPage({LocalKey key, String name}) : super(key: key, name: name);
+
+  @override
+  Route<void> createRoute(BuildContext context) {
+    return PageRouteBuilder<void>(
+      settings: this,
+      pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) => const Placeholder(),
+    );
+  }
+}

packages/flutter/test/widgets/router_test.dart

@@ -663,12 +663,12 @@ class SimpleNavigatorRouterDelegate extends RouterDelegate<RouteInformation> wit
       pages: <Page<void>>[
         // We need at least two pages for the pop to propagate through.
         // Otherwise, the navigator will bubble the pop to the system navigator.
-        MaterialPage<void>(
-          builder: (BuildContext context) => const Text('base'),
+        const MaterialPage<void>(
+          child: Text('base'),
         ),
         MaterialPage<void>(
           key: ValueKey<String>(routeInformation?.location),
-          builder: (BuildContext context) => builder(context, routeInformation),
+          child: builder(context, routeInformation),
         )
       ],
     );

packages/flutter/test/widgets/routes_test.dart

@@ -542,142 +542,6 @@ void main() {
     expect(focusNode.hasPrimaryFocus, isTrue);
   });
 
-  testWidgets('TransitionBuilderPage works', (WidgetTester tester) async {
-    final LocalKey pageKey = UniqueKey();
-    final TransitionDetector detector = TransitionDetector();
-    List<Page<void>> myPages = <Page<void>>[
-      TransitionBuilderPage<void>(
-        key: pageKey,
-        pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-          return const Text('first');
-        },
-      )
-    ];
-    await tester.pumpWidget(
-      buildNavigator(
-        pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
-        transitionDelegate: detector,
-      )
-    );
-
-    expect(detector.hasTransition, isFalse);
-    expect(find.text('first'), findsOneWidget);
-
-    myPages = <Page<void>>[
-      TransitionBuilderPage<void>(
-        key: pageKey,
-        pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-          return const Text('second');
-        },
-      )
-    ];
-
-    await tester.pumpWidget(
-      buildNavigator(
-        pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
-        transitionDelegate: detector,
-      )
-    );
-    // There should be no transition because the page has the same key.
-    expect(detector.hasTransition, isFalse);
-    // The content does update.
-    expect(find.text('first'), findsNothing);
-    expect(find.text('second'), findsOneWidget);
-
-    myPages = <Page<void>>[
-      TransitionBuilderPage<void>(
-        key: pageKey,
-        pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-          return const Text('dummy');
-        },
-        transitionsBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
-          // Purposely discard the input child.
-          return const Text('third');
-        }
-      )
-    ];
-
-    await tester.pumpWidget(
-      buildNavigator(
-        pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
-        transitionDelegate: detector,
-      )
-    );
-
-    // There should be no transition because the page has the same key.
-    expect(detector.hasTransition, isFalse);
-    // Makes sure transitionsBuilder works.
-    expect(find.text('second'), findsNothing);
-    expect(find.text('dummy'), findsNothing);
-    expect(find.text('third'), findsOneWidget);
-  });
-
-  testWidgets('TransitionBuilderPage can toggle MaintainState', (WidgetTester tester) async {
-    final LocalKey pageKeyOne = UniqueKey();
-    final LocalKey pageKeyTwo = UniqueKey();
-    final TransitionDetector detector = TransitionDetector();
-    List<Page<void>> myPages = <Page<void>>[
-      TransitionBuilderPage<void>(
-        key: pageKeyOne,
-        maintainState: false,
-        pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-          return const Text('first');
-        },
-      ),
-      TransitionBuilderPage<void>(
-        key: pageKeyTwo,
-        pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-          return const Text('second');
-        },
-      )
-    ];
-    await tester.pumpWidget(
-      buildNavigator(
-        pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
-        transitionDelegate: detector,
-      )
-    );
-
-    expect(detector.hasTransition, isFalse);
-    // Page one does not maintain state.
-    expect(find.text('first', skipOffstage: false), findsNothing);
-    expect(find.text('second'), findsOneWidget);
-
-    myPages = <Page<void>>[
-      TransitionBuilderPage<void>(
-        key: pageKeyOne,
-        maintainState: true,
-        pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-          return const Text('first');
-        },
-      ),
-      TransitionBuilderPage<void>(
-        key: pageKeyTwo,
-        pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
-          return const Text('second');
-        },
-      )
-    ];
-
-    await tester.pumpWidget(
-      buildNavigator(
-        pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
-        transitionDelegate: detector,
-      )
-    );
-    // There should be no transition because the page has the same key.
-    expect(detector.hasTransition, isFalse);
-    // Page one sets the maintain state to be true, its widget tree should be
-    // built.
-    expect(find.text('first', skipOffstage: false), findsOneWidget);
-    expect(find.text('second'), findsOneWidget);
-  });
-
   group('PageRouteBuilder', () {
     testWidgets('reverseTransitionDuration defaults to 300ms', (WidgetTester tester) async {
       // Default PageRouteBuilder reverse transition duration should be 300ms.