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Why this matters: If you navigate back to a page with a Scrollable that has a nonzero scrollOffset, we will restore that scrollOffset. We clamp the scrollOffset to the contentExtent before the first layout, before contentExtent is updated to its proper value. Initializing contentExtent to INFINITY effectively disables the first clamp, until we can get a valid value from layout. Since the previous scrollOffset was valid, it seems safe to assume it's still valid. BUG=https://github.com/flutter/flutter/issues/4883 BUG=https://github.com/flutter/flutter/issues/4797
117 lines
4.3 KiB
Dart
117 lines
4.3 KiB
Dart
// Copyright 2015 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter_test/flutter_test.dart';
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import 'package:flutter/material.dart';
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class ThePositiveNumbers extends StatelessWidget {
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@override
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Widget build(BuildContext context) {
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return new ScrollableLazyList(
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itemExtent: 100.0,
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itemBuilder: (BuildContext context, int start, int count) {
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List<Widget> result = new List<Widget>();
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for (int index = start; index < start + count; index += 1)
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result.add(new Text('$index', key: new ValueKey<int>(index)));
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return result;
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}
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);
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}
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}
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void main() {
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testWidgets('whether we remember our scroll position', (WidgetTester tester) async {
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GlobalKey<NavigatorState> navigatorKey = new GlobalKey<NavigatorState>();
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await tester.pumpWidget(new Navigator(
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key: navigatorKey,
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onGenerateRoute: (RouteSettings settings) {
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if (settings.name == '/') {
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return new MaterialPageRoute<Null>(
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settings: settings,
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builder: (_) => new Container(child: new ThePositiveNumbers())
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);
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} else if (settings.name == '/second') {
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return new MaterialPageRoute<Null>(
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settings: settings,
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builder: (_) => new Container(child: new ThePositiveNumbers())
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);
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}
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return null;
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}
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));
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// we're 600 pixels high, each item is 100 pixels high, scroll position is
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// zero, so we should have exactly 6 items, 0..5.
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expect(find.text('0'), findsOneWidget);
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expect(find.text('1'), findsOneWidget);
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expect(find.text('2'), findsOneWidget);
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expect(find.text('3'), findsOneWidget);
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expect(find.text('4'), findsOneWidget);
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expect(find.text('5'), findsOneWidget);
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expect(find.text('6'), findsNothing);
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expect(find.text('10'), findsNothing);
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expect(find.text('100'), findsNothing);
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ScrollableState targetState = tester.state(find.byType(Scrollable));
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targetState.scrollTo(1000.0);
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await tester.pump(new Duration(seconds: 1));
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// we're 600 pixels high, each item is 100 pixels high, scroll position is
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// 1000, so we should have exactly 6 items, 10..15.
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expect(find.text('0'), findsNothing);
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expect(find.text('8'), findsNothing);
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expect(find.text('9'), findsNothing);
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expect(find.text('10'), findsOneWidget);
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expect(find.text('11'), findsOneWidget);
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expect(find.text('12'), findsOneWidget);
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expect(find.text('13'), findsOneWidget);
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expect(find.text('14'), findsOneWidget);
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expect(find.text('15'), findsOneWidget);
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expect(find.text('16'), findsNothing);
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expect(find.text('100'), findsNothing);
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navigatorKey.currentState.pushNamed('/second');
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await tester.pump(); // navigating always takes two frames
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await tester.pump(new Duration(seconds: 1));
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// same as the first list again
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expect(find.text('0'), findsOneWidget);
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expect(find.text('1'), findsOneWidget);
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expect(find.text('2'), findsOneWidget);
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expect(find.text('3'), findsOneWidget);
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expect(find.text('4'), findsOneWidget);
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expect(find.text('5'), findsOneWidget);
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expect(find.text('6'), findsNothing);
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expect(find.text('10'), findsNothing);
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expect(find.text('100'), findsNothing);
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navigatorKey.currentState.pop();
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await tester.pump(); // navigating always takes two frames
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// Ensure we don't clamp the scroll offset even during the navigation.
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// https://github.com/flutter/flutter/issues/4883
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LazyListViewport viewport = tester.firstWidget(find.byType(LazyListViewport));
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expect(viewport.scrollOffset, equals(1000.0));
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await tester.pump(new Duration(seconds: 1));
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// we're 600 pixels high, each item is 100 pixels high, scroll position is
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// 1000, so we should have exactly 6 items, 10..15.
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expect(find.text('0'), findsNothing);
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expect(find.text('8'), findsNothing);
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expect(find.text('9'), findsNothing);
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expect(find.text('10'), findsOneWidget);
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expect(find.text('11'), findsOneWidget);
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expect(find.text('12'), findsOneWidget);
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expect(find.text('13'), findsOneWidget);
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expect(find.text('14'), findsOneWidget);
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expect(find.text('15'), findsOneWidget);
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expect(find.text('16'), findsNothing);
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expect(find.text('100'), findsNothing);
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});
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}
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