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TabBarView scroll handling should factor in scroll physics tolerance (#9390)

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Hans Muller 2017-04-14 15:23:47 -07:00 committed by GitHub
parent 9fdd4f4701
commit dbfa747b37
2 changed files with 53 additions and 1 deletions
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5
packages/flutter/lib/src/material/tabs.dart
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@ -830,7 +830,10 @@ class _TabBarViewState extends State<TabBarView> {
}
_controller.offset = (_pageController.page - _controller.index).clamp(-1.0, 1.0);
} else if (notification is ScrollEndNotification) {
_controller.index = _pageController.page.floor();
final ScrollPosition position = _pageController.position;
final double pageTolerance = position.physics.tolerance.distance
/ (position.viewportDimension * _pageController.viewportFraction);
_controller.index = (_pageController.page + pageTolerance).floor();
_currentIndex = _controller.index;
}
_warpUnderwayCount -= 1;

49
packages/flutter/test/material/tabs_test.dart
View File

@ -759,4 +759,53 @@ void main() {
controller.index = 1;
await tester.pump(const Duration(milliseconds: 300));
});
testWidgets('TabBarView scrolls end very VERY close to a new page', (WidgetTester tester) async {
// This is a regression test for https://github.com/flutter/flutter/issues/9375
final TabController tabController = new TabController(
vsync: const TestVSync(),
initialIndex: 1,
length: 3,
);
await tester.pumpWidget(
new SizedBox.expand(
child: new Center(
child: new SizedBox(
width: 400.0,
height: 400.0,
child: new TabBarView(
controller: tabController,
children: <Widget>[
const Center(child: const Text('0')),
const Center(child: const Text('1')),
const Center(child: const Text('2')),
],
),
),
),
),
);
expect(tabController.index, 1);
final PageView pageView = tester.widget(find.byType(PageView));
final PageController pageController = pageView.controller;
final ScrollPosition position = pageController.position;
// The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
// page 1 is at 400.0, page 2 is at 800.0.
expect(position.pixels, 400.0);
// Not close enough to switch to page 2
pageController.jumpTo(800.0 - 1.25 * position.physics.tolerance.distance);
expect(tabController.index, 1);
// Close enough to switch to page 2
pageController.jumpTo(800.0 - 0.75 * position.physics.tolerance.distance);
expect(tabController.index, 2);
});
}