packages/flutter/test/widgets/page_view_test.dart - mirrors/flutter - Git at Google

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

 import 'semantics_tester.dart';
 import 'states.dart';

 const Duration _frameDuration = const Duration(milliseconds: 100);

 void main() {
   testWidgets('PageView control test', (WidgetTester tester) async {
     final List<String> log = <String>[];

     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new PageView(
         children: kStates.map<Widget>((String state) {
           return new GestureDetector(
             onTap: () {
               log.add(state);
             },
             child: new Container(
               height: 200.0,
               color: const Color(0xFF0000FF),
               child: new Text(state),
             ),
           );
         }).toList(),
       ),
     ));

     await tester.tap(find.text('Alabama'));
     expect(log, equals(<String>['Alabama']));
     log.clear();

     expect(find.text('Alaska'), findsNothing);

     await tester.drag(find.byType(PageView), const Offset(-20.0, 0.0));
     await tester.pump();

     expect(find.text('Alabama'), findsOneWidget);
     expect(find.text('Alaska'), findsOneWidget);
     expect(find.text('Arizona'), findsNothing);

     await tester.pumpAndSettle(_frameDuration);

     expect(find.text('Alabama'), findsOneWidget);
     expect(find.text('Alaska'), findsNothing);

     await tester.drag(find.byType(PageView), const Offset(-401.0, 0.0));
     await tester.pumpAndSettle(_frameDuration);

     expect(find.text('Alabama'), findsNothing);
     expect(find.text('Alaska'), findsOneWidget);
     expect(find.text('Arizona'), findsNothing);

     await tester.tap(find.text('Alaska'));
     expect(log, equals(<String>['Alaska']));
     log.clear();

     await tester.fling(find.byType(PageView), const Offset(-200.0, 0.0), 1000.0);
     await tester.pumpAndSettle(_frameDuration);

     expect(find.text('Alabama'), findsNothing);
     expect(find.text('Alaska'), findsNothing);
     expect(find.text('Arizona'), findsOneWidget);

     await tester.fling(find.byType(PageView), const Offset(200.0, 0.0), 1000.0);
     await tester.pumpAndSettle(_frameDuration);

     expect(find.text('Alabama'), findsNothing);
     expect(find.text('Alaska'), findsOneWidget);
     expect(find.text('Arizona'), findsNothing);
   });

   testWidgets('PageView does not squish when overscrolled',
       (WidgetTester tester) async {
     await tester.pumpWidget(new MaterialApp(
       theme: new ThemeData(platform: TargetPlatform.iOS),
       home: new PageView(
         children: new List<Widget>.generate(10, (int i) {
           return new Container(
             key: new ValueKey<int>(i),
             color: const Color(0xFF0000FF),
           );
         }),
       ),
     ));

     Size sizeOf(int i) => tester.getSize(find.byKey(new ValueKey<int>(i)));
     double leftOf(int i) => tester.getTopLeft(find.byKey(new ValueKey<int>(i))).dx;

     expect(leftOf(0), equals(0.0));
     expect(sizeOf(0), equals(const Size(800.0, 600.0)));

     // Going into overscroll.
     await tester.drag(find.byType(PageView), const Offset(100.0, 0.0));
     await tester.pump();

     expect(leftOf(0), greaterThan(0.0));
     expect(sizeOf(0), equals(const Size(800.0, 600.0)));

     // Easing overscroll past overscroll limit.
     await tester.drag(find.byType(PageView), const Offset(-200.0, 0.0));
     await tester.pump();

     expect(leftOf(0), lessThan(0.0));
     expect(sizeOf(0), equals(const Size(800.0, 600.0)));
   });

   testWidgets('PageController control test', (WidgetTester tester) async {
     final PageController controller = new PageController(initialPage: 4);

     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new Center(
         child: new SizedBox(
           width: 600.0,
           height: 400.0,
           child: new PageView(
             controller: controller,
             children: kStates.map<Widget>((String state) => new Text(state)).toList(),
           ),
         ),
       ),
     ));

     expect(find.text('California'), findsOneWidget);

     controller.nextPage(duration: const Duration(milliseconds: 150), curve: Curves.ease);
     await tester.pumpAndSettle(const Duration(milliseconds: 100));

     expect(find.text('Colorado'), findsOneWidget);

     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new Center(
         child: new SizedBox(
           width: 300.0,
           height: 400.0,
           child: new PageView(
             controller: controller,
             children: kStates.map<Widget>((String state) => new Text(state)).toList(),
           ),
         ),
       ),
     ));

     expect(find.text('Colorado'), findsOneWidget);

     controller.previousPage(duration: const Duration(milliseconds: 150), curve: Curves.ease);
     await tester.pumpAndSettle(const Duration(milliseconds: 100));

     expect(find.text('California'), findsOneWidget);
   });

   testWidgets('PageController page stability', (WidgetTester tester) async {
     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new Center(
         child: new SizedBox(
           width: 600.0,
           height: 400.0,
           child: new PageView(
             children: kStates.map<Widget>((String state) => new Text(state)).toList(),
           ),
         )
       ),
     ));

     expect(find.text('Alabama'), findsOneWidget);

     await tester.drag(find.byType(PageView), const Offset(-1250.0, 0.0));
     await tester.pumpAndSettle(const Duration(milliseconds: 100));

     expect(find.text('Arizona'), findsOneWidget);

     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new Center(
         child: new SizedBox(
           width: 250.0,
           height: 100.0,
           child: new PageView(
             children: kStates.map<Widget>((String state) => new Text(state)).toList(),
           ),
         ),
       ),
     ));

     expect(find.text('Arizona'), findsOneWidget);

     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new Center(
         child: new SizedBox(
           width: 450.0,
           height: 400.0,
           child: new PageView(
             children: kStates.map<Widget>((String state) => new Text(state)).toList(),
           ),
         ),
       ),
     ));

     expect(find.text('Arizona'), findsOneWidget);
   });

   testWidgets('PageController nextPage and previousPage return Futures that resolve', (WidgetTester tester) async {
     final PageController controller = new PageController();
     await tester.pumpWidget(new Directionality(
         textDirection: TextDirection.ltr,
         child: new PageView(
           controller: controller,
           children: kStates.map<Widget>((String state) => new Text(state)).toList(),
         ),
     ));

     bool nextPageCompleted = false;
     controller.nextPage(duration: const Duration(milliseconds: 150), curve: Curves.ease)
         .then((_) => nextPageCompleted = true);

     expect(nextPageCompleted, false);
     await tester.pump(const Duration(milliseconds: 200));
     expect(nextPageCompleted, false);
     await tester.pump(const Duration(milliseconds: 200));
     expect(nextPageCompleted, true);


     bool previousPageCompleted = false;
     controller.previousPage(duration: const Duration(milliseconds: 150), curve: Curves.ease)
         .then((_) => previousPageCompleted = true);

     expect(previousPageCompleted, false);
     await tester.pump(const Duration(milliseconds: 200));
     expect(previousPageCompleted, false);
     await tester.pump(const Duration(milliseconds: 200));
     expect(previousPageCompleted, true);
   });

   testWidgets('PageView in zero-size container', (WidgetTester tester) async {
     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new Center(
         child: new SizedBox(
           width: 0.0,
           height: 0.0,
           child: new PageView(
             children: kStates.map<Widget>((String state) => new Text(state)).toList(),
           ),
         ),
       ),
     ));

     expect(find.text('Alabama', skipOffstage: false), findsOneWidget);

     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new Center(
         child: new SizedBox(
           width: 200.0,
           height: 200.0,
           child: new PageView(
             children: kStates.map<Widget>((String state) => new Text(state)).toList(),
           ),
         ),
       ),
     ));

     expect(find.text('Alabama'), findsOneWidget);
   });

   testWidgets('Page changes at halfway point', (WidgetTester tester) async {
     final List<int> log = <int>[];
     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new PageView(
         onPageChanged: log.add,
         children: kStates.map<Widget>((String state) => new Text(state)).toList(),
       ),
     ));

     expect(log, isEmpty);

     final TestGesture gesture =
         await tester.startGesture(const Offset(100.0, 100.0));
     // The page view is 800.0 wide, so this move is just short of halfway.
     await gesture.moveBy(const Offset(-380.0, 0.0));

     expect(log, isEmpty);

     // We've crossed the halfway mark.
     await gesture.moveBy(const Offset(-40.0, 0.0));

     expect(log, equals(const <int>[1]));
     log.clear();

     // Moving a bit more should not generate redundant notifications.
     await gesture.moveBy(const Offset(-40.0, 0.0));

     expect(log, isEmpty);

     await gesture.moveBy(const Offset(-40.0, 0.0));
     await tester.pump();

     await gesture.moveBy(const Offset(-40.0, 0.0));
     await tester.pump();

     await gesture.moveBy(const Offset(-40.0, 0.0));
     await tester.pump();

     expect(log, isEmpty);

     await gesture.up();
     await tester.pumpAndSettle();

     expect(log, isEmpty);

     expect(find.text('Alabama'), findsNothing);
     expect(find.text('Alaska'), findsOneWidget);
   });

   testWidgets('Bouncing scroll physics ballistics does not overshoot', (WidgetTester tester) async {
     final List<int> log = <int>[];
     final PageController controller = new PageController(viewportFraction: 0.9);

     Widget build(PageController controller, {Size size}) {
       final Widget pageView = new Directionality(
         textDirection: TextDirection.ltr,
         child: new PageView(
           controller: controller,
           onPageChanged: log.add,
           physics: const BouncingScrollPhysics(),
           children: kStates.map<Widget>((String state) => new Text(state)).toList(),
         ),
       );

       if (size != null) {
         return new OverflowBox(
           child: pageView,
           minWidth: size.width,
           minHeight: size.height,
           maxWidth: size.width,
           maxHeight: size.height,
         );
       } else {
         return pageView;
       }
     }

     await tester.pumpWidget(build(controller));
     expect(log, isEmpty);

     // Fling right to move to a non-existent page at the beginning of the
     // PageView, and confirm that the PageView settles back on the first page.
     await tester.fling(find.byType(PageView), const Offset(100.0, 0.0), 800.0);
     await tester.pumpAndSettle();
     expect(log, isEmpty);

     expect(find.text('Alabama'), findsOneWidget);
     expect(find.text('Alaska'), findsOneWidget);
     expect(find.text('Arizona'), findsNothing);

     // Try again with a Cupertino "Plus" device size.
     await tester.pumpWidget(build(controller, size: const Size(414.0, 736.0)));
     expect(log, isEmpty);

     await tester.fling(find.byType(PageView), const Offset(100.0, 0.0), 800.0);
     await tester.pumpAndSettle();
     expect(log, isEmpty);

     expect(find.text('Alabama'), findsOneWidget);
     expect(find.text('Alaska'), findsOneWidget);
     expect(find.text('Arizona'), findsNothing);
   });

   testWidgets('PageView viewportFraction', (WidgetTester tester) async {
     PageController controller = new PageController(viewportFraction: 7/8);

     Widget build(PageController controller) {
       return new Directionality(
         textDirection: TextDirection.ltr,
         child: new PageView.builder(
           controller: controller,
           itemCount: kStates.length,
           itemBuilder: (BuildContext context, int index) {
             return new Container(
               height: 200.0,
               color: index % 2 == 0
                   ? const Color(0xFF0000FF)
                   : const Color(0xFF00FF00),
               child: new Text(kStates[index]),
             );
           },
         ),
       );
     }

     await tester.pumpWidget(build(controller));

     expect(tester.getTopLeft(find.text('Alabama')), const Offset(50.0, 0.0));
     expect(tester.getTopLeft(find.text('Alaska')), const Offset(750.0, 0.0));

     controller.jumpToPage(10);
     await tester.pump();

     expect(tester.getTopLeft(find.text('Georgia')), const Offset(-650.0, 0.0));
     expect(tester.getTopLeft(find.text('Hawaii')), const Offset(50.0, 0.0));
     expect(tester.getTopLeft(find.text('Idaho')), const Offset(750.0, 0.0));

     controller = new PageController(viewportFraction: 39/40);

     await tester.pumpWidget(build(controller));

     expect(tester.getTopLeft(find.text('Georgia')), const Offset(-770.0, 0.0));
     expect(tester.getTopLeft(find.text('Hawaii')), const Offset(10.0, 0.0));
     expect(tester.getTopLeft(find.text('Idaho')), const Offset(790.0, 0.0));
   });

   testWidgets('Page snapping disable and reenable', (WidgetTester tester) async {
     final List<int> log = <int>[];

     Widget build({ bool pageSnapping }) {
       return new Directionality(
         textDirection: TextDirection.ltr,
         child: new PageView(
           pageSnapping: pageSnapping,
           onPageChanged: log.add,
           children:
               kStates.map<Widget>((String state) => new Text(state)).toList(),
         ),
       );
     }

     await tester.pumpWidget(build(pageSnapping: true));
     expect(log, isEmpty);

     // Drag more than halfway to the next page, to confirm the default behavior.
     TestGesture gesture = await tester.startGesture(const Offset(100.0, 100.0));
     // The page view is 800.0 wide, so this move is just beyond halfway.
     await gesture.moveBy(const Offset(-420.0, 0.0));

     expect(log, equals(const <int>[1]));
     log.clear();

     // Release the gesture, confirm that the page settles on the next.
     await gesture.up();
     await tester.pumpAndSettle();

     expect(find.text('Alabama'), findsNothing);
     expect(find.text('Alaska'), findsOneWidget);

     // Disable page snapping, and try moving halfway. Confirm it doesn't snap.
     await tester.pumpWidget(build(pageSnapping: false));
     gesture = await tester.startGesture(const Offset(100.0, 100.0));
     // Move just beyond halfway, again.
     await gesture.moveBy(const Offset(-420.0, 0.0));

     // Page notifications still get sent.
     expect(log, equals(const <int>[2]));
     log.clear();

     // Release the gesture, confirm that both pages are visible.
     await gesture.up();
     await tester.pumpAndSettle();

     expect(find.text('Alabama'), findsNothing);
     expect(find.text('Alaska'), findsOneWidget);
     expect(find.text('Arizona'), findsOneWidget);
     expect(find.text('Arkansas'), findsNothing);

     // Now re-enable snapping, confirm that we've settled on a page.
     await tester.pumpWidget(build(pageSnapping: true));
     await tester.pumpAndSettle();

     expect(log, isEmpty);

     expect(find.text('Alaska'), findsNothing);
     expect(find.text('Arizona'), findsOneWidget);
     expect(find.text('Arkansas'), findsNothing);
   });

   testWidgets('PageView small viewportFraction', (WidgetTester tester) async {
     final PageController controller = new PageController(viewportFraction: 1/8);

     Widget build(PageController controller) {
       return new Directionality(
         textDirection: TextDirection.ltr,
         child: new PageView.builder(
           controller: controller,
           itemCount: kStates.length,
           itemBuilder: (BuildContext context, int index) {
             return new Container(
               height: 200.0,
               color: index % 2 == 0
                   ? const Color(0xFF0000FF)
                   : const Color(0xFF00FF00),
               child: new Text(kStates[index]),
             );
           },
         ),
       );
     }

     await tester.pumpWidget(build(controller));

     expect(tester.getTopLeft(find.text('Alabama')), const Offset(350.0, 0.0));
     expect(tester.getTopLeft(find.text('Alaska')), const Offset(450.0, 0.0));
     expect(tester.getTopLeft(find.text('Arizona')), const Offset(550.0, 0.0));
     expect(tester.getTopLeft(find.text('Arkansas')), const Offset(650.0, 0.0));
     expect(tester.getTopLeft(find.text('California')), const Offset(750.0, 0.0));

     controller.jumpToPage(10);
     await tester.pump();

     expect(tester.getTopLeft(find.text('Connecticut')), const Offset(-50.0, 0.0));
     expect(tester.getTopLeft(find.text('Delaware')), const Offset(50.0, 0.0));
     expect(tester.getTopLeft(find.text('Florida')), const Offset(150.0, 0.0));
     expect(tester.getTopLeft(find.text('Georgia')), const Offset(250.0, 0.0));
     expect(tester.getTopLeft(find.text('Hawaii')), const Offset(350.0, 0.0));
     expect(tester.getTopLeft(find.text('Idaho')), const Offset(450.0, 0.0));
     expect(tester.getTopLeft(find.text('Illinois')), const Offset(550.0, 0.0));
     expect(tester.getTopLeft(find.text('Indiana')), const Offset(650.0, 0.0));
     expect(tester.getTopLeft(find.text('Iowa')), const Offset(750.0, 0.0));
   });

   testWidgets('PageView large viewportFraction', (WidgetTester tester) async {
     final PageController controller =
         new PageController(viewportFraction: 5/4);

     Widget build(PageController controller) {
       return new Directionality(
         textDirection: TextDirection.ltr,
         child: new PageView.builder(
           controller: controller,
           itemCount: kStates.length,
           itemBuilder: (BuildContext context, int index) {
             return new Container(
               height: 200.0,
               color: index % 2 == 0
                   ? const Color(0xFF0000FF)
                   : const Color(0xFF00FF00),
               child: new Text(kStates[index]),
             );
           },
         ),
       );
     }

     await tester.pumpWidget(build(controller));

     expect(tester.getTopLeft(find.text('Alabama')), const Offset(-100.0, 0.0));
     expect(tester.getBottomRight(find.text('Alabama')), const Offset(900.0, 600.0));

     controller.jumpToPage(10);
     await tester.pump();

     expect(tester.getTopLeft(find.text('Hawaii')), const Offset(-100.0, 0.0));
   });

   testWidgets('PageView does not report page changed on overscroll',
       (WidgetTester tester) async {
     final PageController controller = new PageController(
       initialPage: kStates.length - 1,
     );
     int changeIndex = 0;
     Widget build() {
       return new Directionality(
         textDirection: TextDirection.ltr,
         child: new PageView(
           children:
               kStates.map<Widget>((String state) => new Text(state)).toList(),
           controller: controller,
           onPageChanged: (int page) {
             changeIndex = page;
           },
         ),
       );
     }

     await tester.pumpWidget(build());
     controller.jumpToPage(kStates.length * 2); // try to move beyond max range
     // change index should be zero, shouldn't fire onPageChanged
     expect(changeIndex, 0);
     await tester.pump();
     expect(changeIndex, 0);
   });

   testWidgets('PageView can restore page',
       (WidgetTester tester) async {
     final PageController controller = new PageController();
     try {
       controller.page;
       fail('Accessing page before attaching should fail.');
     } on AssertionError catch (e) {
       expect(
         e.message,
         'PageController.page cannot be accessed before a PageView is built with it.',
       );
     }
     final PageStorageBucket bucket = new PageStorageBucket();
     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new PageStorage(
         bucket: bucket,
         child: new PageView(
           key: const PageStorageKey<String>('PageView'),
           controller: controller,
           children: const <Widget>[
             const Placeholder(),
             const Placeholder(),
             const Placeholder(),
           ],
         ),
       ),
     ));
     expect(controller.page, 0);
     controller.jumpToPage(2);
     expect(await tester.pumpAndSettle(const Duration(minutes: 1)), 1);
     expect(controller.page, 2);
     await tester.pumpWidget(
       new PageStorage(
         bucket: bucket,
         child: new Container(),
       ),
     );
     try {
       controller.page;
       fail('Accessing page after detaching all PageViews should fail.');
     } on AssertionError catch (e) {
       expect(
         e.message,
         'PageController.page cannot be accessed before a PageView is built with it.',
       );
     }
     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new PageStorage(
         bucket: bucket,
         child: new PageView(
           key: const PageStorageKey<String>('PageView'),
           controller: controller,
           children: const <Widget>[
             const Placeholder(),
             const Placeholder(),
             const Placeholder(),
           ],
         ),
       ),
     ));
     expect(controller.page, 2);

     final PageController controller2 = new PageController(keepPage: false);
     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new PageStorage(
         bucket: bucket,
         child: new PageView(
           key: const PageStorageKey<String>('Check it again against your list and see consistency!'),
           controller: controller2,
           children: const <Widget>[
             const Placeholder(),
             const Placeholder(),
             const Placeholder(),
           ],
         ),
       ),
     ));
     expect(controller2.page, 0);
   });

   testWidgets('PageView exposes semantics of children', (WidgetTester tester) async {
     final SemanticsTester semantics = new SemanticsTester(tester);

     final PageController controller = new PageController();
     await tester.pumpWidget(new Directionality(
       textDirection: TextDirection.ltr,
       child: new PageView(
           controller: controller,
           children: new List<Widget>.generate(3, (int i) {
             return new Semantics(
               child: new Text('Page #$i'),
               container: true,
             );
           })
         ),
     ));
     expect(controller.page, 0);

     expect(semantics, includesNodeWith(label: 'Page #0'));
     expect(semantics, isNot(includesNodeWith(label: 'Page #1')));
     expect(semantics, isNot(includesNodeWith(label: 'Page #2')));

     controller.jumpToPage(1);
     await tester.pumpAndSettle();

     expect(semantics, isNot(includesNodeWith(label: 'Page #0')));
     expect(semantics, includesNodeWith(label: 'Page #1'));
     expect(semantics, isNot(includesNodeWith(label: 'Page #2')));

     controller.jumpToPage(2);
     await tester.pumpAndSettle();

     expect(semantics, isNot(includesNodeWith(label: 'Page #0')));
     expect(semantics, isNot(includesNodeWith(label: 'Page #1')));
     expect(semantics, includesNodeWith(label: 'Page #2'));

     semantics.dispose();
   });

   testWidgets('PageMetrics', (WidgetTester tester) async {
     final PageMetrics page = new PageMetrics(
       minScrollExtent: 100.0,
       maxScrollExtent: 200.0,
       pixels: 150.0,
       viewportDimension: 25.0,
       axisDirection: AxisDirection.right,
       viewportFraction: 1.0,
     );
     expect(page.page, 6);
     final PageMetrics page2 = page.copyWith(
       pixels: page.pixels - 100.0,
     );
     expect(page2.page, 4.0);
   });
 }
	// Copyright 2017 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'package:flutter_test/flutter_test.dart';
	import 'package:flutter/material.dart';
	import 'package:flutter/rendering.dart';
	import 'package:flutter/widgets.dart';

	import 'semantics_tester.dart';
	import 'states.dart';

	const Duration _frameDuration = const Duration(milliseconds: 100);

	void main() {
	testWidgets('PageView control test', (WidgetTester tester) async {
	final List<String> log = <String>[];

	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView(
	children: kStates.map<Widget>((String state) {
	return new GestureDetector(
	onTap: () {
	log.add(state);
	},
	child: new Container(
	height: 200.0,
	color: const Color(0xFF0000FF),
	child: new Text(state),
	),
	);
	}).toList(),
	),
	));

	await tester.tap(find.text('Alabama'));
	expect(log, equals(<String>['Alabama']));
	log.clear();

	expect(find.text('Alaska'), findsNothing);

	await tester.drag(find.byType(PageView), const Offset(-20.0, 0.0));
	await tester.pump();

	expect(find.text('Alabama'), findsOneWidget);
	expect(find.text('Alaska'), findsOneWidget);
	expect(find.text('Arizona'), findsNothing);

	await tester.pumpAndSettle(_frameDuration);

	expect(find.text('Alabama'), findsOneWidget);
	expect(find.text('Alaska'), findsNothing);

	await tester.drag(find.byType(PageView), const Offset(-401.0, 0.0));
	await tester.pumpAndSettle(_frameDuration);

	expect(find.text('Alabama'), findsNothing);
	expect(find.text('Alaska'), findsOneWidget);
	expect(find.text('Arizona'), findsNothing);

	await tester.tap(find.text('Alaska'));
	expect(log, equals(<String>['Alaska']));
	log.clear();

	await tester.fling(find.byType(PageView), const Offset(-200.0, 0.0), 1000.0);
	await tester.pumpAndSettle(_frameDuration);

	expect(find.text('Alabama'), findsNothing);
	expect(find.text('Alaska'), findsNothing);
	expect(find.text('Arizona'), findsOneWidget);

	await tester.fling(find.byType(PageView), const Offset(200.0, 0.0), 1000.0);
	await tester.pumpAndSettle(_frameDuration);

	expect(find.text('Alabama'), findsNothing);
	expect(find.text('Alaska'), findsOneWidget);
	expect(find.text('Arizona'), findsNothing);
	});

	testWidgets('PageView does not squish when overscrolled',
	(WidgetTester tester) async {
	await tester.pumpWidget(new MaterialApp(
	theme: new ThemeData(platform: TargetPlatform.iOS),
	home: new PageView(
	children: new List<Widget>.generate(10, (int i) {
	return new Container(
	key: new ValueKey<int>(i),
	color: const Color(0xFF0000FF),
	);
	}),
	),
	));

	Size sizeOf(int i) => tester.getSize(find.byKey(new ValueKey<int>(i)));
	double leftOf(int i) => tester.getTopLeft(find.byKey(new ValueKey<int>(i))).dx;

	expect(leftOf(0), equals(0.0));
	expect(sizeOf(0), equals(const Size(800.0, 600.0)));

	// Going into overscroll.
	await tester.drag(find.byType(PageView), const Offset(100.0, 0.0));
	await tester.pump();

	expect(leftOf(0), greaterThan(0.0));
	expect(sizeOf(0), equals(const Size(800.0, 600.0)));

	// Easing overscroll past overscroll limit.
	await tester.drag(find.byType(PageView), const Offset(-200.0, 0.0));
	await tester.pump();

	expect(leftOf(0), lessThan(0.0));
	expect(sizeOf(0), equals(const Size(800.0, 600.0)));
	});

	testWidgets('PageController control test', (WidgetTester tester) async {
	final PageController controller = new PageController(initialPage: 4);

	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new Center(
	child: new SizedBox(
	width: 600.0,
	height: 400.0,
	child: new PageView(
	controller: controller,
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	),
	),
	));

	expect(find.text('California'), findsOneWidget);

	controller.nextPage(duration: const Duration(milliseconds: 150), curve: Curves.ease);
	await tester.pumpAndSettle(const Duration(milliseconds: 100));

	expect(find.text('Colorado'), findsOneWidget);

	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new Center(
	child: new SizedBox(
	width: 300.0,
	height: 400.0,
	child: new PageView(
	controller: controller,
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	),
	),
	));

	expect(find.text('Colorado'), findsOneWidget);

	controller.previousPage(duration: const Duration(milliseconds: 150), curve: Curves.ease);
	await tester.pumpAndSettle(const Duration(milliseconds: 100));

	expect(find.text('California'), findsOneWidget);
	});

	testWidgets('PageController page stability', (WidgetTester tester) async {
	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new Center(
	child: new SizedBox(
	width: 600.0,
	height: 400.0,
	child: new PageView(
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	)
	),
	));

	expect(find.text('Alabama'), findsOneWidget);

	await tester.drag(find.byType(PageView), const Offset(-1250.0, 0.0));
	await tester.pumpAndSettle(const Duration(milliseconds: 100));

	expect(find.text('Arizona'), findsOneWidget);

	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new Center(
	child: new SizedBox(
	width: 250.0,
	height: 100.0,
	child: new PageView(
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	),
	),
	));

	expect(find.text('Arizona'), findsOneWidget);

	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new Center(
	child: new SizedBox(
	width: 450.0,
	height: 400.0,
	child: new PageView(
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	),
	),
	));

	expect(find.text('Arizona'), findsOneWidget);
	});

	testWidgets('PageController nextPage and previousPage return Futures that resolve', (WidgetTester tester) async {
	final PageController controller = new PageController();
	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView(
	controller: controller,
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	));

	bool nextPageCompleted = false;
	controller.nextPage(duration: const Duration(milliseconds: 150), curve: Curves.ease)
	.then((_) => nextPageCompleted = true);

	expect(nextPageCompleted, false);
	await tester.pump(const Duration(milliseconds: 200));
	expect(nextPageCompleted, false);
	await tester.pump(const Duration(milliseconds: 200));
	expect(nextPageCompleted, true);


	bool previousPageCompleted = false;
	controller.previousPage(duration: const Duration(milliseconds: 150), curve: Curves.ease)
	.then((_) => previousPageCompleted = true);

	expect(previousPageCompleted, false);
	await tester.pump(const Duration(milliseconds: 200));
	expect(previousPageCompleted, false);
	await tester.pump(const Duration(milliseconds: 200));
	expect(previousPageCompleted, true);
	});

	testWidgets('PageView in zero-size container', (WidgetTester tester) async {
	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new Center(
	child: new SizedBox(
	width: 0.0,
	height: 0.0,
	child: new PageView(
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	),
	),
	));

	expect(find.text('Alabama', skipOffstage: false), findsOneWidget);

	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new Center(
	child: new SizedBox(
	width: 200.0,
	height: 200.0,
	child: new PageView(
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	),
	),
	));

	expect(find.text('Alabama'), findsOneWidget);
	});

	testWidgets('Page changes at halfway point', (WidgetTester tester) async {
	final List<int> log = <int>[];
	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView(
	onPageChanged: log.add,
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	));

	expect(log, isEmpty);

	final TestGesture gesture =
	await tester.startGesture(const Offset(100.0, 100.0));
	// The page view is 800.0 wide, so this move is just short of halfway.
	await gesture.moveBy(const Offset(-380.0, 0.0));

	expect(log, isEmpty);

	// We've crossed the halfway mark.
	await gesture.moveBy(const Offset(-40.0, 0.0));

	expect(log, equals(const <int>[1]));
	log.clear();

	// Moving a bit more should not generate redundant notifications.
	await gesture.moveBy(const Offset(-40.0, 0.0));

	expect(log, isEmpty);

	await gesture.moveBy(const Offset(-40.0, 0.0));
	await tester.pump();

	await gesture.moveBy(const Offset(-40.0, 0.0));
	await tester.pump();

	await gesture.moveBy(const Offset(-40.0, 0.0));
	await tester.pump();

	expect(log, isEmpty);

	await gesture.up();
	await tester.pumpAndSettle();

	expect(log, isEmpty);

	expect(find.text('Alabama'), findsNothing);
	expect(find.text('Alaska'), findsOneWidget);
	});

	testWidgets('Bouncing scroll physics ballistics does not overshoot', (WidgetTester tester) async {
	final List<int> log = <int>[];
	final PageController controller = new PageController(viewportFraction: 0.9);

	Widget build(PageController controller, {Size size}) {
	final Widget pageView = new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView(
	controller: controller,
	onPageChanged: log.add,
	physics: const BouncingScrollPhysics(),
	children: kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	);

	if (size != null) {
	return new OverflowBox(
	child: pageView,
	minWidth: size.width,
	minHeight: size.height,
	maxWidth: size.width,
	maxHeight: size.height,
	);
	} else {
	return pageView;
	}
	}

	await tester.pumpWidget(build(controller));
	expect(log, isEmpty);

	// Fling right to move to a non-existent page at the beginning of the
	// PageView, and confirm that the PageView settles back on the first page.
	await tester.fling(find.byType(PageView), const Offset(100.0, 0.0), 800.0);
	await tester.pumpAndSettle();
	expect(log, isEmpty);

	expect(find.text('Alabama'), findsOneWidget);
	expect(find.text('Alaska'), findsOneWidget);
	expect(find.text('Arizona'), findsNothing);

	// Try again with a Cupertino "Plus" device size.
	await tester.pumpWidget(build(controller, size: const Size(414.0, 736.0)));
	expect(log, isEmpty);

	await tester.fling(find.byType(PageView), const Offset(100.0, 0.0), 800.0);
	await tester.pumpAndSettle();
	expect(log, isEmpty);

	expect(find.text('Alabama'), findsOneWidget);
	expect(find.text('Alaska'), findsOneWidget);
	expect(find.text('Arizona'), findsNothing);
	});

	testWidgets('PageView viewportFraction', (WidgetTester tester) async {
	PageController controller = new PageController(viewportFraction: 7/8);

	Widget build(PageController controller) {
	return new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView.builder(
	controller: controller,
	itemCount: kStates.length,
	itemBuilder: (BuildContext context, int index) {
	return new Container(
	height: 200.0,
	color: index % 2 == 0
	? const Color(0xFF0000FF)
	: const Color(0xFF00FF00),
	child: new Text(kStates[index]),
	);
	},
	),
	);
	}

	await tester.pumpWidget(build(controller));

	expect(tester.getTopLeft(find.text('Alabama')), const Offset(50.0, 0.0));
	expect(tester.getTopLeft(find.text('Alaska')), const Offset(750.0, 0.0));

	controller.jumpToPage(10);
	await tester.pump();

	expect(tester.getTopLeft(find.text('Georgia')), const Offset(-650.0, 0.0));
	expect(tester.getTopLeft(find.text('Hawaii')), const Offset(50.0, 0.0));
	expect(tester.getTopLeft(find.text('Idaho')), const Offset(750.0, 0.0));

	controller = new PageController(viewportFraction: 39/40);

	await tester.pumpWidget(build(controller));

	expect(tester.getTopLeft(find.text('Georgia')), const Offset(-770.0, 0.0));
	expect(tester.getTopLeft(find.text('Hawaii')), const Offset(10.0, 0.0));
	expect(tester.getTopLeft(find.text('Idaho')), const Offset(790.0, 0.0));
	});

	testWidgets('Page snapping disable and reenable', (WidgetTester tester) async {
	final List<int> log = <int>[];

	Widget build({ bool pageSnapping }) {
	return new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView(
	pageSnapping: pageSnapping,
	onPageChanged: log.add,
	children:
	kStates.map<Widget>((String state) => new Text(state)).toList(),
	),
	);
	}

	await tester.pumpWidget(build(pageSnapping: true));
	expect(log, isEmpty);

	// Drag more than halfway to the next page, to confirm the default behavior.
	TestGesture gesture = await tester.startGesture(const Offset(100.0, 100.0));
	// The page view is 800.0 wide, so this move is just beyond halfway.
	await gesture.moveBy(const Offset(-420.0, 0.0));

	expect(log, equals(const <int>[1]));
	log.clear();

	// Release the gesture, confirm that the page settles on the next.
	await gesture.up();
	await tester.pumpAndSettle();

	expect(find.text('Alabama'), findsNothing);
	expect(find.text('Alaska'), findsOneWidget);

	// Disable page snapping, and try moving halfway. Confirm it doesn't snap.
	await tester.pumpWidget(build(pageSnapping: false));
	gesture = await tester.startGesture(const Offset(100.0, 100.0));
	// Move just beyond halfway, again.
	await gesture.moveBy(const Offset(-420.0, 0.0));

	// Page notifications still get sent.
	expect(log, equals(const <int>[2]));
	log.clear();

	// Release the gesture, confirm that both pages are visible.
	await gesture.up();
	await tester.pumpAndSettle();

	expect(find.text('Alabama'), findsNothing);
	expect(find.text('Alaska'), findsOneWidget);
	expect(find.text('Arizona'), findsOneWidget);
	expect(find.text('Arkansas'), findsNothing);

	// Now re-enable snapping, confirm that we've settled on a page.
	await tester.pumpWidget(build(pageSnapping: true));
	await tester.pumpAndSettle();

	expect(log, isEmpty);

	expect(find.text('Alaska'), findsNothing);
	expect(find.text('Arizona'), findsOneWidget);
	expect(find.text('Arkansas'), findsNothing);
	});

	testWidgets('PageView small viewportFraction', (WidgetTester tester) async {
	final PageController controller = new PageController(viewportFraction: 1/8);

	Widget build(PageController controller) {
	return new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView.builder(
	controller: controller,
	itemCount: kStates.length,
	itemBuilder: (BuildContext context, int index) {
	return new Container(
	height: 200.0,
	color: index % 2 == 0
	? const Color(0xFF0000FF)
	: const Color(0xFF00FF00),
	child: new Text(kStates[index]),
	);
	},
	),
	);
	}

	await tester.pumpWidget(build(controller));

	expect(tester.getTopLeft(find.text('Alabama')), const Offset(350.0, 0.0));
	expect(tester.getTopLeft(find.text('Alaska')), const Offset(450.0, 0.0));
	expect(tester.getTopLeft(find.text('Arizona')), const Offset(550.0, 0.0));
	expect(tester.getTopLeft(find.text('Arkansas')), const Offset(650.0, 0.0));
	expect(tester.getTopLeft(find.text('California')), const Offset(750.0, 0.0));

	controller.jumpToPage(10);
	await tester.pump();

	expect(tester.getTopLeft(find.text('Connecticut')), const Offset(-50.0, 0.0));
	expect(tester.getTopLeft(find.text('Delaware')), const Offset(50.0, 0.0));
	expect(tester.getTopLeft(find.text('Florida')), const Offset(150.0, 0.0));
	expect(tester.getTopLeft(find.text('Georgia')), const Offset(250.0, 0.0));
	expect(tester.getTopLeft(find.text('Hawaii')), const Offset(350.0, 0.0));
	expect(tester.getTopLeft(find.text('Idaho')), const Offset(450.0, 0.0));
	expect(tester.getTopLeft(find.text('Illinois')), const Offset(550.0, 0.0));
	expect(tester.getTopLeft(find.text('Indiana')), const Offset(650.0, 0.0));
	expect(tester.getTopLeft(find.text('Iowa')), const Offset(750.0, 0.0));
	});

	testWidgets('PageView large viewportFraction', (WidgetTester tester) async {
	final PageController controller =
	new PageController(viewportFraction: 5/4);

	Widget build(PageController controller) {
	return new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView.builder(
	controller: controller,
	itemCount: kStates.length,
	itemBuilder: (BuildContext context, int index) {
	return new Container(
	height: 200.0,
	color: index % 2 == 0
	? const Color(0xFF0000FF)
	: const Color(0xFF00FF00),
	child: new Text(kStates[index]),
	);
	},
	),
	);
	}

	await tester.pumpWidget(build(controller));

	expect(tester.getTopLeft(find.text('Alabama')), const Offset(-100.0, 0.0));
	expect(tester.getBottomRight(find.text('Alabama')), const Offset(900.0, 600.0));

	controller.jumpToPage(10);
	await tester.pump();

	expect(tester.getTopLeft(find.text('Hawaii')), const Offset(-100.0, 0.0));
	});

	testWidgets('PageView does not report page changed on overscroll',
	(WidgetTester tester) async {
	final PageController controller = new PageController(
	initialPage: kStates.length - 1,
	);
	int changeIndex = 0;
	Widget build() {
	return new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView(
	children:
	kStates.map<Widget>((String state) => new Text(state)).toList(),
	controller: controller,
	onPageChanged: (int page) {
	changeIndex = page;
	},
	),
	);
	}

	await tester.pumpWidget(build());
	controller.jumpToPage(kStates.length * 2); // try to move beyond max range
	// change index should be zero, shouldn't fire onPageChanged
	expect(changeIndex, 0);
	await tester.pump();
	expect(changeIndex, 0);
	});

	testWidgets('PageView can restore page',
	(WidgetTester tester) async {
	final PageController controller = new PageController();
	try {
	controller.page;
	fail('Accessing page before attaching should fail.');
	} on AssertionError catch (e) {
	expect(
	e.message,
	'PageController.page cannot be accessed before a PageView is built with it.',
	);
	}
	final PageStorageBucket bucket = new PageStorageBucket();
	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageStorage(
	bucket: bucket,
	child: new PageView(
	key: const PageStorageKey<String>('PageView'),
	controller: controller,
	children: const <Widget>[
	const Placeholder(),
	const Placeholder(),
	const Placeholder(),
	],
	),
	),
	));
	expect(controller.page, 0);
	controller.jumpToPage(2);
	expect(await tester.pumpAndSettle(const Duration(minutes: 1)), 1);
	expect(controller.page, 2);
	await tester.pumpWidget(
	new PageStorage(
	bucket: bucket,
	child: new Container(),
	),
	);
	try {
	controller.page;
	fail('Accessing page after detaching all PageViews should fail.');
	} on AssertionError catch (e) {
	expect(
	e.message,
	'PageController.page cannot be accessed before a PageView is built with it.',
	);
	}
	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageStorage(
	bucket: bucket,
	child: new PageView(
	key: const PageStorageKey<String>('PageView'),
	controller: controller,
	children: const <Widget>[
	const Placeholder(),
	const Placeholder(),
	const Placeholder(),
	],
	),
	),
	));
	expect(controller.page, 2);

	final PageController controller2 = new PageController(keepPage: false);
	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageStorage(
	bucket: bucket,
	child: new PageView(
	key: const PageStorageKey<String>('Check it again against your list and see consistency!'),
	controller: controller2,
	children: const <Widget>[
	const Placeholder(),
	const Placeholder(),
	const Placeholder(),
	],
	),
	),
	));
	expect(controller2.page, 0);
	});

	testWidgets('PageView exposes semantics of children', (WidgetTester tester) async {
	final SemanticsTester semantics = new SemanticsTester(tester);

	final PageController controller = new PageController();
	await tester.pumpWidget(new Directionality(
	textDirection: TextDirection.ltr,
	child: new PageView(
	controller: controller,
	children: new List<Widget>.generate(3, (int i) {
	return new Semantics(
	child: new Text('Page #$i'),
	container: true,
	);
	})
	),
	));
	expect(controller.page, 0);

	expect(semantics, includesNodeWith(label: 'Page #0'));
	expect(semantics, isNot(includesNodeWith(label: 'Page #1')));
	expect(semantics, isNot(includesNodeWith(label: 'Page #2')));

	controller.jumpToPage(1);
	await tester.pumpAndSettle();

	expect(semantics, isNot(includesNodeWith(label: 'Page #0')));
	expect(semantics, includesNodeWith(label: 'Page #1'));
	expect(semantics, isNot(includesNodeWith(label: 'Page #2')));

	controller.jumpToPage(2);
	await tester.pumpAndSettle();

	expect(semantics, isNot(includesNodeWith(label: 'Page #0')));
	expect(semantics, isNot(includesNodeWith(label: 'Page #1')));
	expect(semantics, includesNodeWith(label: 'Page #2'));

	semantics.dispose();
	});

	testWidgets('PageMetrics', (WidgetTester tester) async {
	final PageMetrics page = new PageMetrics(
	minScrollExtent: 100.0,
	maxScrollExtent: 200.0,
	pixels: 150.0,
	viewportDimension: 25.0,
	axisDirection: AxisDirection.right,
	viewportFraction: 1.0,
	);
	expect(page.page, 6);
	final PageMetrics page2 = page.copyWith(
	pixels: page.pixels - 100.0,
	);
	expect(page2.page, 4.0);
	});
	}