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Fix issues when correcting the scroll offset (#8211)

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Previously, the scroll correction code path was untested. This patch
introduces a test for the code path and fixes two issues with it.
There's likely more work we'll need to do in this area to nail down all
the cases.

Fixes #8155
This commit is contained in:
Adam Barth 2017-02-15 21:01:13 -08:00 committed by GitHub
parent 03ae2cf366
commit f93daa4f3d
3 changed files with 59 additions and 2 deletions
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1
packages/flutter/lib/src/rendering/sliver.dart
View file

@ -481,7 +481,6 @@ class SliverGeometry {
assert(visible != null);
assert(hasVisualOverflow != null);
assert(scrollOffsetCorrection != null);
assert(scrollOffsetCorrection == 0.0);
return true;
}

4
packages/flutter/lib/src/rendering/sliver_list.dart
View file

@ -73,8 +73,10 @@ class RenderSliverList extends RenderSliverMultiBoxAdaptor {
// We must inform our parent that this sliver cannot fulfill
// its contract and that we need a scroll offset correction.
geometry = new SliverGeometry(
scrollOffsetCorrection: -childScrollOffset(firstChild),
scrollOffsetCorrection: -scrollOffset,
);
final SliverMultiBoxAdaptorParentData childParentData = firstChild.parentData;
childParentData.layoutOffset = 0.0;
return;
}
final SliverMultiBoxAdaptorParentData childParentData = earliestUsefulChild.parentData;

56
packages/flutter/test/widgets/list_view_correction_test.dart Normal file
View file

@ -0,0 +1,56 @@
// Copyright 2016 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';
void main() {
testWidgets('ListView can handle shrinking top elements', (WidgetTester tester) async {
final ScrollController controller = new ScrollController();
await tester.pumpWidget(new ListView(
controller: controller,
children: <Widget>[
new Container(height: 400.0, child: new Text('1')),
new Container(height: 400.0, child: new Text('2')),
new Container(height: 400.0, child: new Text('3')),
new Container(height: 400.0, child: new Text('4')),
new Container(height: 400.0, child: new Text('5')),
new Container(height: 400.0, child: new Text('6')),
],
));
controller.jumpTo(1000.0);
await tester.pump();
expect(tester.getTopLeft(find.text('4')).y, equals(200.0));
await tester.pumpWidget(new ListView(
controller: controller,
children: <Widget>[
new Container(height: 200.0, child: new Text('1')),
new Container(height: 400.0, child: new Text('2')),
new Container(height: 400.0, child: new Text('3')),
new Container(height: 400.0, child: new Text('4')),
new Container(height: 400.0, child: new Text('5')),
new Container(height: 400.0, child: new Text('6')),
],
));
expect(controller.offset, equals(1000.0));
expect(tester.getTopLeft(find.text('4')).y, equals(200.0));
controller.jumpTo(300.0);
await tester.pump();
expect(tester.getTopLeft(find.text('2')).y, equals(100.0));
controller.jumpTo(50.0);
await tester.pump();
expect(controller.offset, equals(0.0));
expect(tester.getTopLeft(find.text('2')).y, equals(200.0));
});
}