Add "navigator" option to "showDialog" and "showGeneralDialog" (#42842)

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

@@ -864,6 +864,10 @@ class _CupertinoModalPopupRoute<T> extends PopupRoute<T> {
 /// It is only used when the method is called. Its corresponding widget can be
 /// safely removed from the tree before the popup is closed.
 ///
+/// The `useRootNavigator` argument is used to determine whether to push the
+/// popup to the [Navigator] furthest from or nearest to the given `context`. It
+/// is `false` by default.
+///
 /// The `builder` argument typically builds a [CupertinoActionSheet] widget.
 /// Content below the widget is dimmed with a [ModalBarrier]. The widget built
 /// by the `builder` does not share a context with the location that
@@ -882,8 +886,10 @@ class _CupertinoModalPopupRoute<T> extends PopupRoute<T> {
 Future<T> showCupertinoModalPopup<T>({
   @required BuildContext context,
   @required WidgetBuilder builder,
+  bool useRootNavigator = true,
 }) {
-  return Navigator.of(context, rootNavigator: true).push(
+  assert(useRootNavigator != null);
+  return Navigator.of(context, rootNavigator: useRootNavigator).push(
     _CupertinoModalPopupRoute<T>(
       builder: builder,
       barrierLabel: 'Dismiss',
@@ -933,14 +939,18 @@ Widget _buildCupertinoDialogTransitions(BuildContext context, Animation<double>
 /// It is only used when the method is called. Its corresponding widget can
 /// be safely removed from the tree before the dialog is closed.
 ///
-/// Returns a [Future] that resolves to the value (if any) that was passed to
-/// [Navigator.pop] when the dialog was closed.
+/// The `useRootNavigator` argument is used to determine whether to push the
+/// dialog to the [Navigator] furthest from or nearest to the given `context`.
+/// By default, `useRootNavigator` is `true` and the dialog route created by
+/// this method is pushed to the root navigator.
 ///
-/// The dialog route created by this method is pushed to the root navigator.
 /// If the application has multiple [Navigator] objects, it may be necessary to
 /// call `Navigator.of(context, rootNavigator: true).pop(result)` to close the
 /// dialog rather than just `Navigator.pop(context, result)`.
 ///
+/// Returns a [Future] that resolves to the value (if any) that was passed to
+/// [Navigator.pop] when the dialog was closed.
+///
 /// See also:
 ///
 ///  * [CupertinoDialog], an iOS-style dialog.
@@ -951,8 +961,10 @@ Widget _buildCupertinoDialogTransitions(BuildContext context, Animation<double>
 Future<T> showCupertinoDialog<T>({
   @required BuildContext context,
   @required WidgetBuilder builder,
+  bool useRootNavigator = true,
 }) {
   assert(builder != null);
+  assert(useRootNavigator != null);
   return showGeneralDialog(
     context: context,
     barrierDismissible: false,
@@ -963,5 +975,6 @@ Future<T> showCupertinoDialog<T>({
       return builder(context);
     },
     transitionBuilder: _buildCupertinoDialogTransitions,
+    useRootNavigator: useRootNavigator,
   );
 }

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

@@ -223,8 +223,8 @@ class AboutListTile extends StatelessWidget {
 /// The licenses shown on the [LicensePage] are those returned by the
 /// [LicenseRegistry] API, which can be used to add more licenses to the list.
 ///
-/// The `context` argument is passed to [showDialog], the documentation for
-/// which discusses how it is used.
+/// The [context] and [useRootNavigator] arguments are passed to [showDialog],
+/// the documentation for which discusses how it is used.
 void showAboutDialog({
   @required BuildContext context,
   String applicationName,
@@ -232,10 +232,13 @@ void showAboutDialog({
   Widget applicationIcon,
   String applicationLegalese,
   List<Widget> children,
+  bool useRootNavigator = true,
 }) {
   assert(context != null);
+  assert(useRootNavigator != null);
   showDialog<void>(
     context: context,
+    useRootNavigator: useRootNavigator,
     builder: (BuildContext context) {
       return AboutDialog(
         applicationName: applicationName,
@@ -251,7 +254,13 @@ void showAboutDialog({
 /// Displays a [LicensePage], which shows licenses for software used by the
 /// application.
 ///
-/// The arguments correspond to the properties on [LicensePage].
+/// The application arguments correspond to the properties on [LicensePage].
+///
+/// The `context` argument is used to look up the [Navigator] for the page.
+///
+/// The `useRootNavigator` argument is used to determine whether to push the
+/// page to the [Navigator] furthest from or nearest to the given `context`. It
+/// is `false` by default.
 ///
 /// If the application has a [Drawer], consider using [AboutListTile] instead
 /// of calling this directly.
@@ -267,9 +276,11 @@ void showLicensePage({
   String applicationVersion,
   Widget applicationIcon,
   String applicationLegalese,
+  bool useRootNavigator = false,
 }) {
   assert(context != null);
-  Navigator.push(context, MaterialPageRoute<void>(
+  assert(useRootNavigator != null);
+  Navigator.of(context, rootNavigator: useRootNavigator).push(MaterialPageRoute<void>(
     builder: (BuildContext context) => LicensePage(
       applicationName: applicationName,
       applicationVersion: applicationVersion,

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

@@ -1085,8 +1085,8 @@ typedef SelectableDayPredicate = bool Function(DateTime day);
 /// provided by [Directionality]. If both [locale] and [textDirection] are not
 /// null, [textDirection] overrides the direction chosen for the [locale].
 ///
-/// The [context] argument is passed to [showDialog], the documentation for
-/// which discusses how it is used.
+/// The [context] and [useRootNavigator] arguments are passed to [showDialog],
+/// the documentation for which discusses how it is used.
 ///
 /// The [builder] parameter can be used to wrap the dialog widget
 /// to add inherited widgets like [Theme].
@@ -1133,10 +1133,12 @@ Future<DateTime> showDatePicker({
   Locale locale,
   TextDirection textDirection,
   TransitionBuilder builder,
+  bool useRootNavigator = true,
 }) async {
   assert(initialDate != null);
   assert(firstDate != null);
   assert(lastDate != null);
+  assert(useRootNavigator != null);
   assert(!initialDate.isBefore(firstDate), 'initialDate must be on or after firstDate');
   assert(!initialDate.isAfter(lastDate), 'initialDate must be on or before lastDate');
   assert(!firstDate.isAfter(lastDate), 'lastDate must be on or after firstDate');
@@ -1173,6 +1175,7 @@ Future<DateTime> showDatePicker({
 
   return await showDialog<DateTime>(
     context: context,
+    useRootNavigator: useRootNavigator,
     builder: (BuildContext context) {
       return builder == null ? child : builder(context, child);
     },

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

@@ -655,20 +655,24 @@ Widget _buildMaterialDialogTransitions(BuildContext context, Animation<double> a
 /// `showDialog` is originally called from. Use a [StatefulBuilder] or a
 /// custom [StatefulWidget] if the dialog needs to update dynamically.
 ///
+/// The `child` argument is deprecated, and should be replaced with `builder`.
+///
 /// The `context` argument is used to look up the [Navigator] and [Theme] for
 /// the dialog. It is only used when the method is called. Its corresponding
 /// widget can be safely removed from the tree before the dialog is closed.
 ///
-/// The `child` argument is deprecated, and should be replaced with `builder`.
+/// The `useRootNavigator` argument is used to determine whether to push the
+/// dialog to the [Navigator] furthest from or nearest to the given `context`.
+/// By default, `useRootNavigator` is `true` and the dialog route created by
+/// this method is pushed to the root navigator.
 ///
-/// Returns a [Future] that resolves to the value (if any) that was passed to
-/// [Navigator.pop] when the dialog was closed.
-///
-/// The dialog route created by this method is pushed to the root navigator.
 /// If the application has multiple [Navigator] objects, it may be necessary to
 /// call `Navigator.of(context, rootNavigator: true).pop(result)` to close the
 /// dialog rather than just `Navigator.pop(context, result)`.
 ///
+/// Returns a [Future] that resolves to the value (if any) that was passed to
+/// [Navigator.pop] when the dialog was closed.
+///
 /// See also:
 ///
 ///  * [AlertDialog], for dialogs that have a row of buttons below a body.
@@ -687,8 +691,10 @@ Future<T> showDialog<T>({
     'is appropriate for widgets built in the dialog.'
   ) Widget child,
   WidgetBuilder builder,
+  bool useRootNavigator = true,
 }) {
   assert(child == null || builder == null);
+  assert(useRootNavigator != null);
   assert(debugCheckHasMaterialLocalizations(context));
 
   final ThemeData theme = Theme.of(context, shadowThemeOnly: true);
@@ -711,5 +717,6 @@ Future<T> showDialog<T>({
     barrierColor: Colors.black54,
     transitionDuration: const Duration(milliseconds: 150),
     transitionBuilder: _buildMaterialDialogTransitions,
+    useRootNavigator: useRootNavigator,
   );
 }

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

@@ -790,6 +790,10 @@ class _PopupMenuRoute<T> extends PopupRoute<T> {
 /// the menu. It is only used when the method is called. Its corresponding
 /// widget can be safely removed from the tree before the popup menu is closed.
 ///
+/// The `useRootNavigator` argument is used to determine whether to push the
+/// menu to the [Navigator] furthest from or nearest to the given `context`. It
+/// is `false` by default.
+///
 /// The `semanticLabel` argument is used by accessibility frameworks to
 /// announce screen transitions when the menu is opened and closed. If this
 /// label is not provided, it will default to
@@ -814,9 +818,11 @@ Future<T> showMenu<T>({
   ShapeBorder shape,
   Color color,
   bool captureInheritedThemes = true,
+  bool useRootNavigator = false,
 }) {
   assert(context != null);
   assert(position != null);
+  assert(useRootNavigator != null);
   assert(items != null && items.isNotEmpty);
   assert(captureInheritedThemes != null);
   assert(debugCheckHasMaterialLocalizations(context));
@@ -831,7 +837,7 @@ Future<T> showMenu<T>({
       label = semanticLabel ?? MaterialLocalizations.of(context)?.popupMenuLabel;
   }
 
-  return Navigator.push(context, _PopupMenuRoute<T>(
+  return Navigator.of(context, rootNavigator: useRootNavigator).push(_PopupMenuRoute<T>(
     position: position,
     items: items,
     initialValue: initialValue,

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

@@ -1731,8 +1731,8 @@ class _TimePickerDialogState extends State<_TimePickerDialog> {
 /// ```
 /// {@end-tool}
 ///
-/// The [context] argument is passed to [showDialog], the documentation for
-/// which discusses how it is used.
+/// The [context] and [useRootNavigator] arguments are passed to [showDialog],
+/// the documentation for which discusses how it is used.
 ///
 /// The [builder] parameter can be used to wrap the dialog widget
 /// to add inherited widgets like [Localizations.override],
@@ -1780,14 +1780,17 @@ Future<TimeOfDay> showTimePicker({
   @required BuildContext context,
   @required TimeOfDay initialTime,
   TransitionBuilder builder,
+  bool useRootNavigator = true,
 }) async {
   assert(context != null);
   assert(initialTime != null);
+  assert(useRootNavigator != null);
   assert(debugCheckHasMaterialLocalizations(context));
 
   final Widget dialog = _TimePickerDialog(initialTime: initialTime);
   return await showDialog<TimeOfDay>(
     context: context,
+    useRootNavigator: useRootNavigator,
     builder: (BuildContext context) {
       return builder == null ? dialog : builder(context, dialog);
     },

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

@@ -1560,9 +1560,18 @@ class _DialogRoute<T> extends PopupRoute<T> {
 /// [StatefulWidget] if the dialog needs to update dynamically. The
 /// `pageBuilder` argument can not be null.
 ///
-/// The `context` argument is used to look up the [Navigator] for the dialog.
-/// It is only used when the method is called. Its corresponding widget can
-/// be safely removed from the tree before the dialog is closed.
+/// The `context` argument is used to look up the [Navigator] for the
+/// dialog. It is only used when the method is called. Its corresponding widget
+/// can be safely removed from the tree before the dialog is closed.
+///
+/// The `useRootNavigator` argument is used to determine whether to push the
+/// dialog to the [Navigator] furthest from or nearest to the given `context`.
+/// By default, `useRootNavigator` is `true` and the dialog route created by
+/// this method is pushed to the root navigator.
+///
+/// If the application has multiple [Navigator] objects, it may be necessary to
+/// call `Navigator.of(context, rootNavigator: true).pop(result)` to close the
+/// dialog rather than just `Navigator.pop(context, result)`.
 ///
 /// The `barrierDismissible` argument is used to determine whether this route
 /// can be dismissed by tapping the modal barrier. This argument defaults
@@ -1586,11 +1595,6 @@ class _DialogRoute<T> extends PopupRoute<T> {
 /// Returns a [Future] that resolves to the value (if any) that was passed to
 /// [Navigator.pop] when the dialog was closed.
 ///
-/// The dialog route created by this method is pushed to the root navigator.
-/// If the application has multiple [Navigator] objects, it may be necessary to
-/// call `Navigator.of(context, rootNavigator: true).pop(result)` to close the
-/// dialog rather than just `Navigator.pop(context, result)`.
-///
 /// See also:
 ///
 ///  * [showDialog], which displays a Material-style dialog.
@@ -1603,10 +1607,12 @@ Future<T> showGeneralDialog<T>({
   Color barrierColor,
   Duration transitionDuration,
   RouteTransitionsBuilder transitionBuilder,
+  bool useRootNavigator = true,
 }) {
   assert(pageBuilder != null);
+  assert(useRootNavigator != null);
   assert(!barrierDismissible || barrierLabel != null);
-  return Navigator.of(context, rootNavigator: true).push<T>(_DialogRoute<T>(
+  return Navigator.of(context, rootNavigator: useRootNavigator).push<T>(_DialogRoute<T>(
     pageBuilder: pageBuilder,
     barrierDismissible: barrierDismissible,
     barrierLabel: barrierLabel,

packages/flutter/test/cupertino/route_test.dart

@@ -918,6 +918,164 @@ void main() {
     expect(homeTapCount, 1);
     expect(pageTapCount, 1);
   });
+
+  testWidgets('showCupertinoModalPopup uses root navigator by default', (WidgetTester tester) async {
+    final PopupObserver rootObserver = PopupObserver();
+    final PopupObserver nestedObserver = PopupObserver();
+
+    await tester.pumpWidget(CupertinoApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return PageRouteBuilder<dynamic>(
+            pageBuilder: (BuildContext context, Animation<double> _, Animation<double> __) {
+              return GestureDetector(
+                onTap: () async {
+                  await showCupertinoModalPopup<void>(
+                    context: context,
+                    builder: (BuildContext context) => const SizedBox(),
+                  );
+                },
+                child: const Text('tap'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.text('tap'));
+
+    expect(rootObserver.popupCount, 1);
+    expect(nestedObserver.popupCount, 0);
+  });
+
+  testWidgets('showCupertinoModalPopup uses nested navigator if useRootNavigator is false', (WidgetTester tester) async {
+    final PopupObserver rootObserver = PopupObserver();
+    final PopupObserver nestedObserver = PopupObserver();
+
+    await tester.pumpWidget(CupertinoApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return PageRouteBuilder<dynamic>(
+            pageBuilder: (BuildContext context, Animation<double> _, Animation<double> __) {
+              return GestureDetector(
+                onTap: () async {
+                  await showCupertinoModalPopup<void>(
+                    context: context,
+                    useRootNavigator: false,
+                    builder: (BuildContext context) => const SizedBox(),
+                  );
+                },
+                child: const Text('tap'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.text('tap'));
+
+    expect(rootObserver.popupCount, 0);
+    expect(nestedObserver.popupCount, 1);
+  });
+
+  testWidgets('showCupertinoDialog uses root navigator by default', (WidgetTester tester) async {
+    final DialogObserver rootObserver = DialogObserver();
+    final DialogObserver nestedObserver = DialogObserver();
+
+    await tester.pumpWidget(CupertinoApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return PageRouteBuilder<dynamic>(
+            pageBuilder: (BuildContext context, Animation<double> _, Animation<double> __) {
+              return GestureDetector(
+                onTap: () async {
+                  await showCupertinoDialog<void>(
+                    context: context,
+                    builder: (BuildContext context) => const SizedBox(),
+                  );
+                },
+                child: const Text('tap'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.text('tap'));
+
+    expect(rootObserver.dialogCount, 1);
+    expect(nestedObserver.dialogCount, 0);
+  });
+
+  testWidgets('showCupertinoDialog uses nested navigator if useRootNavigator is false', (WidgetTester tester) async {
+    final DialogObserver rootObserver = DialogObserver();
+    final DialogObserver nestedObserver = DialogObserver();
+
+    await tester.pumpWidget(CupertinoApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return PageRouteBuilder<dynamic>(
+            pageBuilder: (BuildContext context, Animation<double> _, Animation<double> __) {
+              return GestureDetector(
+                onTap: () async {
+                  await showCupertinoDialog<void>(
+                    context: context,
+                    useRootNavigator: false,
+                    builder: (BuildContext context) => const SizedBox(),
+                  );
+                },
+                child: const Text('tap'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.text('tap'));
+
+    expect(rootObserver.dialogCount, 0);
+    expect(nestedObserver.dialogCount, 1);
+  });
 }
 
 class MockNavigatorObserver extends Mock implements NavigatorObserver {}
+
+class PopupObserver extends NavigatorObserver {
+  int popupCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route.toString().contains('_CupertinoModalPopupRoute')) {
+      popupCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
+}
+
+class DialogObserver extends NavigatorObserver {
+  int dialogCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route.toString().contains('_DialogRoute')) {
+      dialogCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
+}

packages/flutter/test/material/about_test.dart

@@ -305,6 +305,150 @@ void main() {
     tileRect = tester.getRect(find.byType(AboutListTile));
     expect(tileRect.height, 48.0);
   });
+
+  testWidgets('showLicensePage uses nested navigator by default', (WidgetTester tester) async {
+    final LicensePageObserver rootObserver = LicensePageObserver();
+    final LicensePageObserver nestedObserver = LicensePageObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      initialRoute: '/',
+      onGenerateRoute: (_) {
+        return PageRouteBuilder<dynamic>(
+          pageBuilder: (_, __, ___) => Navigator(
+            observers: <NavigatorObserver>[nestedObserver],
+            onGenerateRoute: (RouteSettings settings) {
+              return PageRouteBuilder<dynamic>(
+                pageBuilder: (BuildContext context, _, __) {
+                  return RaisedButton(
+                    onPressed: () {
+                      showLicensePage(
+                        context: context,
+                        applicationName: 'A',
+                      );
+                    },
+                    child: const Text('Show License Page'),
+                  );
+                },
+              );
+            },
+          ),
+        );
+      },
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.licensePageCount, 0);
+    expect(nestedObserver.licensePageCount, 1);
+  });
+
+  testWidgets('showLicensePage uses root navigator if useRootNavigator is true', (WidgetTester tester) async {
+    final LicensePageObserver rootObserver = LicensePageObserver();
+    final LicensePageObserver nestedObserver = LicensePageObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      initialRoute: '/',
+      onGenerateRoute: (_) {
+        return PageRouteBuilder<dynamic>(
+          pageBuilder: (_, __, ___) => Navigator(
+            observers: <NavigatorObserver>[nestedObserver],
+            onGenerateRoute: (RouteSettings settings) {
+              return PageRouteBuilder<dynamic>(
+                pageBuilder: (BuildContext context, _, __) {
+                  return RaisedButton(
+                    onPressed: () {
+                      showLicensePage(
+                        context: context,
+                        useRootNavigator: true,
+                        applicationName: 'A',
+                      );
+                    },
+                    child: const Text('Show License Page'),
+                  );
+                },
+              );
+            },
+          ),
+        );
+      },
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.licensePageCount, 1);
+    expect(nestedObserver.licensePageCount, 0);
+  });
+
+  testWidgets('showAboutDialog uses root navigator by default', (WidgetTester tester) async {
+    final AboutDialogObserver rootObserver = AboutDialogObserver();
+    final AboutDialogObserver nestedObserver = AboutDialogObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showAboutDialog(
+                    context: context,
+                    applicationName: 'A',
+                  );
+                },
+                child: const Text('Show About Dialog'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.dialogCount, 1);
+    expect(nestedObserver.dialogCount, 0);
+  });
+
+  testWidgets('showAboutDialog uses nested navigator if useRootNavigator is false', (WidgetTester tester) async {
+    final AboutDialogObserver rootObserver = AboutDialogObserver();
+    final AboutDialogObserver nestedObserver = AboutDialogObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showAboutDialog(
+                    context: context,
+                    useRootNavigator: false,
+                    applicationName: 'A',
+                  );
+                },
+                child: const Text('Show About Dialog'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.dialogCount, 0);
+    expect(nestedObserver.dialogCount, 1);
+  });
 }
 
 class FakeLicenseEntry extends LicenseEntry {
@@ -322,3 +466,27 @@ class FakeLicenseEntry extends LicenseEntry {
     return <LicenseParagraph>[];
   }
 }
+
+class LicensePageObserver extends NavigatorObserver {
+  int licensePageCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route is MaterialPageRoute<dynamic>) {
+      licensePageCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
+}
+
+class AboutDialogObserver extends NavigatorObserver {
+  int dialogCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route.toString().contains('_DialogRoute')) {
+      dialogCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
+}

packages/flutter/test/material/date_picker_test.dart

@@ -897,4 +897,90 @@ void _tests() {
     });
   });
 
+  testWidgets('uses root navigator by default', (WidgetTester tester) async {
+    final DatePickerObserver rootObserver = DatePickerObserver();
+    final DatePickerObserver nestedObserver = DatePickerObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showDatePicker(
+                    context: context,
+                    initialDate: DateTime.now(),
+                    firstDate: DateTime(2018),
+                    lastDate: DateTime(2030),
+                    builder: (BuildContext context, Widget child) {
+                      return const SizedBox();
+                    },
+                  );
+                },
+                child: const Text('Show Date Picker'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.datePickerCount, 1);
+    expect(nestedObserver.datePickerCount, 0);
+  });
+
+  testWidgets('uses nested navigator if useRootNavigator is false', (WidgetTester tester) async {
+    final DatePickerObserver rootObserver = DatePickerObserver();
+    final DatePickerObserver nestedObserver = DatePickerObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showDatePicker(
+                    context: context,
+                    useRootNavigator: false,
+                    initialDate: DateTime.now(),
+                    firstDate: DateTime(2018),
+                    lastDate: DateTime(2030),
+                    builder: (BuildContext context, Widget child) => const SizedBox(),
+                  );
+                },
+                child: const Text('Show Date Picker'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.datePickerCount, 0);
+    expect(nestedObserver.datePickerCount, 1);
+  });
+}
+
+class DatePickerObserver extends NavigatorObserver {
+  int datePickerCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route.toString().contains('_DialogRoute')) {
+      datePickerCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
 }

packages/flutter/test/material/dialog_test.dart

@@ -646,6 +646,77 @@ void main() {
     await tester.pump();
   });
 
+  testWidgets('showDialog uses root navigator by default', (WidgetTester tester) async {
+    final DialogObserver rootObserver = DialogObserver();
+    final DialogObserver nestedObserver = DialogObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showDialog<void>(
+                    context: context,
+                    builder: (BuildContext innerContext) {
+                      return const AlertDialog(title: Text('Title'));
+                    },
+                  );
+                },
+                child: const Text('Show Dialog'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.dialogCount, 1);
+    expect(nestedObserver.dialogCount, 0);
+  });
+
+  testWidgets('showDialog uses nested navigator if useRootNavigator is false', (WidgetTester tester) async {
+    final DialogObserver rootObserver = DialogObserver();
+    final DialogObserver nestedObserver = DialogObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showDialog<void>(
+                    context: context,
+                    useRootNavigator: false,
+                    builder: (BuildContext innerContext) {
+                      return const AlertDialog(title: Text('Title'));
+                    },
+                  );
+                },
+                child: const Text('Show Dialog'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.dialogCount, 0);
+    expect(nestedObserver.dialogCount, 1);
+  });
+
   group('Scrollable title and content', () {
     testWidgets('Title is scrollable', (WidgetTester tester) async {
       final Key titleKey = UniqueKey();
@@ -723,3 +794,15 @@ void main() {
     });
   });
 }
+
+class DialogObserver extends NavigatorObserver {
+  int dialogCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route.toString().contains('_DialogRoute')) {
+      dialogCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
+}

packages/flutter/test/material/popup_menu_test.dart

@@ -1114,6 +1114,83 @@ void main() {
 
     expect(find.text('PopupMenuButton icon'), findsOneWidget);
   });
+
+  testWidgets('showMenu uses nested navigator by default', (WidgetTester tester) async {
+    final MenuObserver rootObserver = MenuObserver();
+    final MenuObserver nestedObserver = MenuObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showMenu<int>(
+                    context: context,
+                    position: const RelativeRect.fromLTRB(0, 0, 0, 0),
+                    items: <PopupMenuItem<int>>[
+                      const PopupMenuItem<int>(
+                        value: 1, child: Text('1'),
+                      ),
+                    ],
+                  );
+                },
+                child: const Text('Show Menu'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.menuCount, 0);
+    expect(nestedObserver.menuCount, 1);
+  });
+
+  testWidgets('showMenu uses root navigator if useRootNavigator is true', (WidgetTester tester) async {
+    final MenuObserver rootObserver = MenuObserver();
+    final MenuObserver nestedObserver = MenuObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showMenu<int>(
+                    context: context,
+                    useRootNavigator: true,
+                    position: const RelativeRect.fromLTRB(0, 0, 0, 0),
+                    items: <PopupMenuItem<int>>[
+                      const PopupMenuItem<int>(
+                        value: 1, child: Text('1'),
+                      ),
+                    ],
+                  );
+                },
+                child: const Text('Show Menu'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.menuCount, 1);
+    expect(nestedObserver.menuCount, 0);
+  });
 }
 
 class TestApp extends StatefulWidget {
@@ -1153,3 +1230,15 @@ class _TestAppState extends State<TestApp> {
     );
   }
 }
+
+class MenuObserver extends NavigatorObserver {
+  int menuCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route.toString().contains('_PopupMenuRoute')) {
+      menuCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
+}

packages/flutter/test/material/time_picker_test.dart

@@ -622,6 +622,73 @@ void _tests() {
     // button and the right edge of the 800 wide window.
     expect(tester.getBottomLeft(find.text('OK')).dx, 800 - ltrOkRight);
   });
+
+  testWidgets('uses root navigator by default', (WidgetTester tester) async {
+    final PickerObserver rootObserver = PickerObserver();
+    final PickerObserver nestedObserver = PickerObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showTimePicker(
+                    context: context,
+                    initialTime: const TimeOfDay(hour: 7, minute: 0),
+                  );
+                },
+                child: const Text('Show Picker'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.pickerCount, 1);
+    expect(nestedObserver.pickerCount, 0);
+  });
+
+  testWidgets('uses nested navigator if useRootNavigator is false', (WidgetTester tester) async {
+    final PickerObserver rootObserver = PickerObserver();
+    final PickerObserver nestedObserver = PickerObserver();
+
+    await tester.pumpWidget(MaterialApp(
+      navigatorObservers: <NavigatorObserver>[rootObserver],
+      home: Navigator(
+        observers: <NavigatorObserver>[nestedObserver],
+        onGenerateRoute: (RouteSettings settings) {
+          return MaterialPageRoute<dynamic>(
+            builder: (BuildContext context) {
+              return RaisedButton(
+                onPressed: () {
+                  showTimePicker(
+                    context: context,
+                    useRootNavigator: false,
+                    initialTime: const TimeOfDay(hour: 7, minute: 0),
+                  );
+                },
+                child: const Text('Show Picker'),
+              );
+            },
+          );
+        },
+      ),
+    ));
+
+    // Open the dialog.
+    await tester.tap(find.byType(RaisedButton));
+
+    expect(rootObserver.pickerCount, 0);
+    expect(nestedObserver.pickerCount, 1);
+  });
 }
 
 final Finder findDialPaint = find.descendant(
@@ -695,3 +762,15 @@ class _CustomPainterSemanticsTester {
     expect(tester.renderObject(findDialPaint), expectedLabels);
   }
 }
+
+class PickerObserver extends NavigatorObserver {
+  int pickerCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route.toString().contains('_DialogRoute')) {
+      pickerCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
+}

packages/flutter/test/widgets/routes_test.dart

@@ -788,6 +788,81 @@ void main() {
       expect(secondaryAnimationPageOne.parent, kAlwaysDismissedAnimation);
       expect(trainHopper2.currentTrain, isNull); // Has been disposed.
     });
+
+    testWidgets('showGeneralDialog uses root navigator by default', (WidgetTester tester) async {
+      final DialogObserver rootObserver = DialogObserver();
+      final DialogObserver nestedObserver = DialogObserver();
+
+      await tester.pumpWidget(MaterialApp(
+        navigatorObservers: <NavigatorObserver>[rootObserver],
+        home: Navigator(
+          observers: <NavigatorObserver>[nestedObserver],
+          onGenerateRoute: (RouteSettings settings) {
+            return MaterialPageRoute<dynamic>(
+              builder: (BuildContext context) {
+                return RaisedButton(
+                  onPressed: () {
+                    showGeneralDialog<void>(
+                      context: context,
+                      barrierDismissible: false,
+                      transitionDuration: Duration.zero,
+                      pageBuilder: (BuildContext innerContext, _, __) {
+                        return const SizedBox();
+                      },
+                    );
+                  },
+                  child: const Text('Show Dialog'),
+                );
+              },
+            );
+          },
+        ),
+      ));
+
+      // Open the dialog.
+      await tester.tap(find.byType(RaisedButton));
+
+      expect(rootObserver.dialogCount, 1);
+      expect(nestedObserver.dialogCount, 0);
+    });
+
+    testWidgets('showGeneralDialog uses nested navigator if useRootNavigator is false', (WidgetTester tester) async {
+      final DialogObserver rootObserver = DialogObserver();
+      final DialogObserver nestedObserver = DialogObserver();
+
+      await tester.pumpWidget(MaterialApp(
+        navigatorObservers: <NavigatorObserver>[rootObserver],
+        home: Navigator(
+          observers: <NavigatorObserver>[nestedObserver],
+          onGenerateRoute: (RouteSettings settings) {
+            return MaterialPageRoute<dynamic>(
+              builder: (BuildContext context) {
+                return RaisedButton(
+                  onPressed: () {
+                    showGeneralDialog<void>(
+                      useRootNavigator: false,
+                      context: context,
+                      barrierDismissible: false,
+                      transitionDuration: Duration.zero,
+                      pageBuilder: (BuildContext innerContext, _, __) {
+                        return const SizedBox();
+                      },
+                    );
+                  },
+                  child: const Text('Show Dialog'),
+                );
+              },
+            );
+          },
+        ),
+      ));
+
+      // Open the dialog.
+      await tester.tap(find.byType(RaisedButton));
+
+      expect(rootObserver.dialogCount, 0);
+      expect(nestedObserver.dialogCount, 1);
+    });
   });
 }
 
@@ -805,3 +880,15 @@ class TestPageRouteBuilder extends PageRouteBuilder<void> {
     return CurvedAnimation(parent: super.createAnimation(), curve: Curves.easeOutExpo);
   }
 }
+
+class DialogObserver extends NavigatorObserver {
+  int dialogCount = 0;
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    if (route.toString().contains('_DialogRoute')) {
+      dialogCount++;
+    }
+    super.didPush(route, previousRoute);
+  }
+}