// Copyright 2015 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 'dart:async'; import 'package:meta/meta.dart'; import 'package:flutter_test/flutter_test.dart'; import 'package:flutter/material.dart'; ScrollController _controller = ScrollController( initialScrollOffset: 110.0, ); class ThePositiveNumbers extends StatelessWidget { const ThePositiveNumbers({ @required this.from }); final int from; @override Widget build(BuildContext context) { return ListView.builder( key: const PageStorageKey<String>('ThePositiveNumbers'), itemExtent: 100.0, controller: _controller, itemBuilder: (BuildContext context, int index) { return Text('${index + from}', key: ValueKey<int>(index)); }, ); } } Future<void> performTest(WidgetTester tester, bool maintainState) async { final GlobalKey<NavigatorState> navigatorKey = GlobalKey<NavigatorState>(); await tester.pumpWidget( Directionality( textDirection: TextDirection.ltr, child: Navigator( key: navigatorKey, onGenerateRoute: (RouteSettings settings) { if (settings.name == '/') { return MaterialPageRoute<void>( settings: settings, builder: (_) => Container(child: const ThePositiveNumbers(from: 0)), maintainState: maintainState, ); } else if (settings.name == '/second') { return MaterialPageRoute<void>( settings: settings, builder: (_) => Container(child: const ThePositiveNumbers(from: 10000)), maintainState: maintainState, ); } return null; }, ), ), ); // we're 600 pixels high, each item is 100 pixels high, scroll position is // 110.0, so we should have 7 items, 1..7. expect(find.text('0'), findsNothing); expect(find.text('1'), findsOneWidget); expect(find.text('2'), findsOneWidget); expect(find.text('3'), findsOneWidget); expect(find.text('4'), findsOneWidget); expect(find.text('5'), findsOneWidget); expect(find.text('6'), findsOneWidget); expect(find.text('7'), findsOneWidget); expect(find.text('8'), findsNothing); expect(find.text('10'), findsNothing); expect(find.text('100'), findsNothing); tester.state<ScrollableState>(find.byType(Scrollable)).position.jumpTo(1000.0); await tester.pump(const Duration(seconds: 1)); // we're 600 pixels high, each item is 100 pixels high, scroll position is // 1000, so we should have exactly 6 items, 10..15. expect(find.text('0'), findsNothing); expect(find.text('1'), findsNothing); expect(find.text('8'), findsNothing); expect(find.text('9'), findsNothing); expect(find.text('10'), findsOneWidget); expect(find.text('11'), findsOneWidget); expect(find.text('12'), findsOneWidget); expect(find.text('13'), findsOneWidget); expect(find.text('14'), findsOneWidget); expect(find.text('15'), findsOneWidget); expect(find.text('16'), findsNothing); expect(find.text('100'), findsNothing); navigatorKey.currentState.pushNamed('/second'); await tester.pump(); // navigating always takes two frames, one to start... await tester.pump(const Duration(seconds: 1)); // ...and one to end the transition // the second list is now visible, starting at 10001 expect(find.text('0'), findsNothing); expect(find.text('1'), findsNothing); expect(find.text('10'), findsNothing); expect(find.text('11'), findsNothing); expect(find.text('10000'), findsNothing); expect(find.text('10001'), findsOneWidget); expect(find.text('10002'), findsOneWidget); expect(find.text('10003'), findsOneWidget); expect(find.text('10004'), findsOneWidget); expect(find.text('10005'), findsOneWidget); expect(find.text('10006'), findsOneWidget); expect(find.text('10007'), findsOneWidget); expect(find.text('10008'), findsNothing); expect(find.text('10010'), findsNothing); expect(find.text('10100'), findsNothing); navigatorKey.currentState.pop(); await tester.pump(); // again, navigating always takes two frames // Ensure we don't clamp the scroll offset even during the navigation. // https://github.com/flutter/flutter/issues/4883 final ScrollableState state = tester.state(find.byType(Scrollable).first); expect(state.position.pixels, equals(1000.0)); await tester.pump(const Duration(seconds: 1)); // we're 600 pixels high, each item is 100 pixels high, scroll position is // 1000, so we should have exactly 6 items, 10..15. expect(find.text('0'), findsNothing); expect(find.text('1'), findsNothing); expect(find.text('8'), findsNothing); expect(find.text('9'), findsNothing); expect(find.text('10'), findsOneWidget); expect(find.text('11'), findsOneWidget); expect(find.text('12'), findsOneWidget); expect(find.text('13'), findsOneWidget); expect(find.text('14'), findsOneWidget); expect(find.text('15'), findsOneWidget); expect(find.text('16'), findsNothing); expect(find.text('100'), findsNothing); } void main() { testWidgets('whether we remember our scroll position', (WidgetTester tester) async { await performTest(tester, true); await performTest(tester, false); }); }