| // Copyright 2014 The Flutter Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // This file contains a wacky demonstration of creating a custom ScrollPosition |
| // setup. It's testing that we don't regress the factoring of the |
| // ScrollPosition/ScrollActivity logic into a state where you can no longer |
| // implement this, e.g. by oversimplifying it or overfitting it to the features |
| // built into the framework itself. |
| |
| import 'dart:collection'; |
| import 'dart:math' as math; |
| |
| import 'package:flutter/material.dart'; |
| import 'package:flutter/rendering.dart'; |
| import 'package:flutter_test/flutter_test.dart'; |
| |
| class LinkedScrollController extends ScrollController { |
| LinkedScrollController({ this.before, this.after }); |
| |
| LinkedScrollController? before; |
| LinkedScrollController? after; |
| |
| ScrollController? _parent; |
| |
| void setParent(ScrollController? newParent) { |
| if (_parent != null) { |
| positions.forEach(_parent!.detach); |
| } |
| _parent = newParent; |
| if (_parent != null) { |
| positions.forEach(_parent!.attach); |
| } |
| } |
| |
| @override |
| void attach(ScrollPosition position) { |
| assert(position is LinkedScrollPosition, 'A LinkedScrollController must only be used with LinkedScrollPositions.'); |
| final LinkedScrollPosition linkedPosition = position as LinkedScrollPosition; |
| assert(linkedPosition.owner == this, 'A LinkedScrollPosition cannot change controllers once created.'); |
| super.attach(position); |
| _parent?.attach(position); |
| } |
| |
| @override |
| void detach(ScrollPosition position) { |
| super.detach(position); |
| _parent?.detach(position); |
| } |
| |
| @override |
| void dispose() { |
| if (_parent != null) { |
| positions.forEach(_parent!.detach); |
| } |
| super.dispose(); |
| } |
| |
| @override |
| LinkedScrollPosition createScrollPosition(ScrollPhysics physics, ScrollContext context, ScrollPosition? oldPosition) { |
| return LinkedScrollPosition( |
| this, |
| physics: physics, |
| context: context, |
| initialPixels: initialScrollOffset, |
| oldPosition: oldPosition, |
| ); |
| } |
| |
| bool get canLinkWithBefore => before != null && before!.hasClients; |
| |
| bool get canLinkWithAfter => after != null && after!.hasClients; |
| |
| Iterable<LinkedScrollActivity> linkWithBefore(LinkedScrollPosition driver) { |
| assert(canLinkWithBefore); |
| return before!.link(driver); |
| } |
| |
| Iterable<LinkedScrollActivity> linkWithAfter(LinkedScrollPosition driver) { |
| assert(canLinkWithAfter); |
| return after!.link(driver); |
| } |
| |
| Iterable<LinkedScrollActivity> link(LinkedScrollPosition driver) sync* { |
| assert(hasClients); |
| for (final LinkedScrollPosition position in positions.cast<LinkedScrollPosition>()) |
| yield position.link(driver); |
| } |
| |
| @override |
| void debugFillDescription(List<String> description) { |
| super.debugFillDescription(description); |
| if (before != null && after != null) { |
| description.add('links: ⬌'); |
| } else if (before != null) { |
| description.add('links: ⬅'); |
| } else if (after != null) { |
| description.add('links: ➡'); |
| } else { |
| description.add('links: none'); |
| } |
| } |
| |
| } |
| |
| class LinkedScrollPosition extends ScrollPositionWithSingleContext { |
| LinkedScrollPosition( |
| this.owner, { |
| required ScrollPhysics physics, |
| required ScrollContext context, |
| required double initialPixels, |
| ScrollPosition? oldPosition, |
| }) : assert(owner != null), |
| super( |
| physics: physics, |
| context: context, |
| initialPixels: initialPixels, |
| oldPosition: oldPosition, |
| ); |
| |
| final LinkedScrollController owner; |
| |
| Set<LinkedScrollActivity>? _beforeActivities; |
| Set<LinkedScrollActivity>? _afterActivities; |
| |
| @override |
| void beginActivity(ScrollActivity? newActivity) { |
| if (newActivity == null) |
| return; |
| if (_beforeActivities != null) { |
| for (final LinkedScrollActivity activity in _beforeActivities!) |
| activity.unlink(this); |
| _beforeActivities!.clear(); |
| } |
| if (_afterActivities != null) { |
| for (final LinkedScrollActivity activity in _afterActivities!) |
| activity.unlink(this); |
| _afterActivities!.clear(); |
| } |
| super.beginActivity(newActivity); |
| } |
| |
| @override |
| void applyUserOffset(double delta) { |
| updateUserScrollDirection(delta > 0.0 ? ScrollDirection.forward : ScrollDirection.reverse); |
| final double value = pixels - physics.applyPhysicsToUserOffset(this, delta); |
| |
| if (value == pixels) |
| return; |
| |
| double beforeOverscroll = 0.0; |
| if (owner.canLinkWithBefore && (value < minScrollExtent)) { |
| final double delta = value - minScrollExtent; |
| _beforeActivities ??= HashSet<LinkedScrollActivity>(); |
| _beforeActivities!.addAll(owner.linkWithBefore(this)); |
| for (final LinkedScrollActivity activity in _beforeActivities!) |
| beforeOverscroll = math.min(activity.moveBy(delta), beforeOverscroll); |
| assert(beforeOverscroll <= 0.0); |
| } |
| |
| double afterOverscroll = 0.0; |
| if (owner.canLinkWithAfter && (value > maxScrollExtent)) { |
| final double delta = value - maxScrollExtent; |
| _afterActivities ??= HashSet<LinkedScrollActivity>(); |
| _afterActivities!.addAll(owner.linkWithAfter(this)); |
| for (final LinkedScrollActivity activity in _afterActivities!) |
| afterOverscroll = math.max(activity.moveBy(delta), afterOverscroll); |
| assert(afterOverscroll >= 0.0); |
| } |
| |
| assert(beforeOverscroll == 0.0 || afterOverscroll == 0.0); |
| |
| final double localOverscroll = setPixels(value.clamp( |
| owner.canLinkWithBefore ? minScrollExtent : -double.infinity, |
| owner.canLinkWithAfter ? maxScrollExtent : double.infinity, |
| )); |
| |
| assert(localOverscroll == 0.0 || (beforeOverscroll == 0.0 && afterOverscroll == 0.0)); |
| } |
| |
| void _userMoved(ScrollDirection direction) { |
| updateUserScrollDirection(direction); |
| } |
| |
| LinkedScrollActivity link(LinkedScrollPosition driver) { |
| if (this.activity is! LinkedScrollActivity) |
| beginActivity(LinkedScrollActivity(this)); |
| final LinkedScrollActivity? activity = this.activity as LinkedScrollActivity?; |
| activity!.link(driver); |
| return activity; |
| } |
| |
| void unlink(LinkedScrollActivity activity) { |
| if (_beforeActivities != null) |
| _beforeActivities!.remove(activity); |
| if (_afterActivities != null) |
| _afterActivities!.remove(activity); |
| } |
| |
| @override |
| void debugFillDescription(List<String> description) { |
| super.debugFillDescription(description); |
| description.add('owner: $owner'); |
| } |
| } |
| |
| class LinkedScrollActivity extends ScrollActivity { |
| LinkedScrollActivity( |
| LinkedScrollPosition delegate, |
| ) : super(delegate); |
| |
| @override |
| LinkedScrollPosition get delegate => super.delegate as LinkedScrollPosition; |
| |
| final Set<LinkedScrollPosition> drivers = HashSet<LinkedScrollPosition>(); |
| |
| void link(LinkedScrollPosition driver) { |
| drivers.add(driver); |
| } |
| |
| void unlink(LinkedScrollPosition driver) { |
| drivers.remove(driver); |
| if (drivers.isEmpty) |
| delegate.goIdle(); |
| } |
| |
| @override |
| bool get shouldIgnorePointer => true; |
| |
| @override |
| bool get isScrolling => true; |
| |
| // LinkedScrollActivity is not self-driven but moved by calls to the [moveBy] |
| // method. |
| @override |
| double get velocity => 0.0; |
| |
| double moveBy(double delta) { |
| assert(drivers.isNotEmpty); |
| ScrollDirection? commonDirection; |
| for (final LinkedScrollPosition driver in drivers) { |
| commonDirection ??= driver.userScrollDirection; |
| if (driver.userScrollDirection != commonDirection) |
| commonDirection = ScrollDirection.idle; |
| } |
| |
| if (commonDirection != null) { |
| delegate._userMoved(commonDirection); |
| } |
| return delegate.setPixels(delegate.pixels + delta); |
| } |
| |
| @override |
| void dispose() { |
| for (final LinkedScrollPosition driver in drivers) |
| driver.unlink(this); |
| super.dispose(); |
| } |
| } |
| |
| class Test extends StatefulWidget { |
| const Test({ Key? key }) : super(key: key); |
| @override |
| State<Test> createState() => _TestState(); |
| } |
| |
| class _TestState extends State<Test> { |
| late LinkedScrollController _beforeController; |
| late LinkedScrollController _afterController; |
| |
| @override |
| void initState() { |
| super.initState(); |
| _beforeController = LinkedScrollController(); |
| _afterController = LinkedScrollController(before: _beforeController); |
| _beforeController.after = _afterController; |
| } |
| |
| @override |
| void didChangeDependencies() { |
| super.didChangeDependencies(); |
| _beforeController.setParent(PrimaryScrollController.of(context)); |
| _afterController.setParent(PrimaryScrollController.of(context)); |
| } |
| |
| @override |
| void dispose() { |
| _beforeController.dispose(); |
| _afterController.dispose(); |
| super.dispose(); |
| } |
| |
| @override |
| Widget build(BuildContext context) { |
| return Directionality( |
| textDirection: TextDirection.ltr, |
| child: Column( |
| children: <Widget>[ |
| Expanded( |
| child: ListView( |
| controller: _beforeController, |
| children: <Widget>[ |
| Container( |
| margin: const EdgeInsets.all(8.0), |
| padding: const EdgeInsets.all(8.0), |
| height: 250.0, |
| color: const Color(0xFF90F090), |
| child: const Center(child: Text('Hello A')), |
| ), |
| Container( |
| margin: const EdgeInsets.all(8.0), |
| padding: const EdgeInsets.all(8.0), |
| height: 250.0, |
| color: const Color(0xFF90F090), |
| child: const Center(child: Text('Hello B')), |
| ), |
| Container( |
| margin: const EdgeInsets.all(8.0), |
| padding: const EdgeInsets.all(8.0), |
| height: 250.0, |
| color: const Color(0xFF90F090), |
| child: const Center(child: Text('Hello C')), |
| ), |
| Container( |
| margin: const EdgeInsets.all(8.0), |
| padding: const EdgeInsets.all(8.0), |
| height: 250.0, |
| color: const Color(0xFF90F090), |
| child: const Center(child: Text('Hello D')), |
| ), |
| ], |
| ), |
| ), |
| const Divider(), |
| Expanded( |
| child: ListView( |
| controller: _afterController, |
| children: <Widget>[ |
| Container( |
| margin: const EdgeInsets.all(8.0), |
| padding: const EdgeInsets.all(8.0), |
| height: 250.0, |
| color: const Color(0xFF9090F0), |
| child: const Center(child: Text('Hello 1')), |
| ), |
| Container( |
| margin: const EdgeInsets.all(8.0), |
| padding: const EdgeInsets.all(8.0), |
| height: 250.0, |
| color: const Color(0xFF9090F0), |
| child: const Center(child: Text('Hello 2')), |
| ), |
| Container( |
| margin: const EdgeInsets.all(8.0), |
| padding: const EdgeInsets.all(8.0), |
| height: 250.0, |
| color: const Color(0xFF9090F0), |
| child: const Center(child: Text('Hello 3')), |
| ), |
| Container( |
| margin: const EdgeInsets.all(8.0), |
| padding: const EdgeInsets.all(8.0), |
| height: 250.0, |
| color: const Color(0xFF9090F0), |
| child: const Center(child: Text('Hello 4')), |
| ), |
| ], |
| ), |
| ), |
| ], |
| ), |
| ); |
| } |
| } |
| |
| void main() { |
| testWidgets('LinkedScrollController - 1', (WidgetTester tester) async { |
| await tester.pumpWidget(const Test()); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.fling(find.text('Hello A'), const Offset(0.0, -50.0), 10000.0); |
| await tester.pumpAndSettle(); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello D'), findsOneWidget); |
| expect(find.text('Hello 4'), findsNothing); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello D'), const Offset(0.0, -10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello D'), findsOneWidget); |
| expect(find.text('Hello 4'), findsOneWidget); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello D'), const Offset(0.0, -10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello D'), findsOneWidget); |
| expect(find.text('Hello 4'), findsOneWidget); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello 4'), const Offset(0.0, -10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello D'), findsOneWidget); |
| expect(find.text('Hello 4'), findsOneWidget); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello D'), const Offset(0.0, 10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 4'), findsOneWidget); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello A'), const Offset(0.0, 10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 4'), findsOneWidget); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello A'), const Offset(0.0, -10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello D'), findsOneWidget); |
| expect(find.text('Hello 4'), findsOneWidget); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello 4'), const Offset(0.0, 10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello 1'), const Offset(0.0, 10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await tester.pump(const Duration(seconds: 2)); |
| await tester.drag(find.text('Hello 1'), const Offset(0.0, -10000.0)); |
| await tester.pump(const Duration(seconds: 2)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 4'), findsOneWidget); |
| }); |
| testWidgets('LinkedScrollController - 2', (WidgetTester tester) async { |
| await tester.pumpWidget(const Test()); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsNothing); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| final TestGesture gestureTop = await tester.startGesture(const Offset(200.0, 150.0)); |
| final TestGesture gestureBottom = await tester.startGesture(const Offset(600.0, 450.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| await gestureTop.moveBy(const Offset(0.0, -270.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsOneWidget); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await gestureBottom.moveBy(const Offset(0.0, -270.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsOneWidget); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsOneWidget); |
| expect(find.text('Hello 4'), findsNothing); |
| await gestureTop.moveBy(const Offset(0.0, -270.0)); |
| await gestureBottom.moveBy(const Offset(0.0, -270.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello B'), findsNothing); |
| expect(find.text('Hello C'), findsOneWidget); |
| expect(find.text('Hello D'), findsOneWidget); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello 2'), findsNothing); |
| expect(find.text('Hello 3'), findsOneWidget); |
| expect(find.text('Hello 4'), findsOneWidget); |
| await gestureTop.moveBy(const Offset(0.0, 270.0)); |
| await gestureBottom.moveBy(const Offset(0.0, 270.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsOneWidget); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsNothing); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsOneWidget); |
| expect(find.text('Hello 4'), findsNothing); |
| await gestureBottom.moveBy(const Offset(0.0, 270.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| expect(find.text('Hello A'), findsNothing); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsOneWidget); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await gestureBottom.moveBy(const Offset(0.0, 50.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsNothing); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await gestureBottom.moveBy(const Offset(0.0, 50.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsNothing); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await gestureBottom.moveBy(const Offset(0.0, 50.0)); |
| await tester.pump(const Duration(seconds: 1)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsNothing); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await gestureTop.moveBy(const Offset(0.0, -270.0)); |
| expect(find.text('Hello A'), findsOneWidget); |
| expect(find.text('Hello B'), findsOneWidget); |
| expect(find.text('Hello C'), findsNothing); |
| expect(find.text('Hello D'), findsNothing); |
| expect(find.text('Hello 1'), findsOneWidget); |
| expect(find.text('Hello 2'), findsOneWidget); |
| expect(find.text('Hello 3'), findsNothing); |
| expect(find.text('Hello 4'), findsNothing); |
| await tester.pump(const Duration(seconds: 1)); |
| await tester.pump(const Duration(seconds: 60)); |
| }); |
| } |