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Fix keepalive for large jumps on tabs and lists. (#21350)

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* Ensure that the _childElements map is properly traversed as a sparse list and not inflated with garbage collected children.

* Add tests to ensure Lists/Tabs with KeepAlive children can make large jumps, don't lose children (including after rebuild).
This commit is contained in:
Dan Field 2018-09-10 21:01:10 -04:00 committed by GitHub
parent 0814e519f8
commit 98ad574d9b
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GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 227 additions and 19 deletions
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6
packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart
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@ -130,8 +130,9 @@ class SliverMultiBoxAdaptorParentData extends SliverLogicalParentData with Conta
/// Whether to keep the child alive even when it is no longer visible.
bool keepAlive = false;
/// Whether the widget is currently in the
/// [RenderSliverMultiBoxAdaptor._keepAliveBucket].
/// Whether the widget is currently being kept alive, i.e. has [keepAlive] set
/// to true and is offscreen.
bool get keptAlive => _keptAlive;
bool _keptAlive = false;
@override
@ -206,6 +207,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
@override
void insert(RenderBox child, { RenderBox after }) {
assert(!_keepAliveBucket.containsValue(child));
super.insert(child, after: after);
assert(firstChild != null);
assert(() {

4
packages/flutter/lib/src/widgets/automatic_keep_alive.dart
View File

@ -89,6 +89,9 @@ class _AutomaticKeepAliveState extends State<AutomaticKeepAlive> {
// build of this subtree. Wait until the end of the frame to update
// the child when the child is guaranteed to be present.
SchedulerBinding.instance.addPostFrameCallback((Duration timeStamp) {
if (!mounted) {
return;
}
final ParentDataElement<SliverMultiBoxAdaptorWidget> childElement = _getChildElement();
assert(childElement != null);
_updateParentDataOfChild(childElement);
@ -103,6 +106,7 @@ class _AutomaticKeepAliveState extends State<AutomaticKeepAlive> {
/// While this widget is guaranteed to have a child, this may return null if
/// the first build of that child has not completed yet.
ParentDataElement<SliverMultiBoxAdaptorWidget> _getChildElement() {
assert(mounted);
final Element element = context;
Element childElement;
// We use Element.visitChildren rather than context.visitChildElements

20
packages/flutter/lib/src/widgets/sliver.dart
View File

@ -756,24 +756,24 @@ class SliverMultiBoxAdaptorElement extends RenderObjectElement implements Render
_currentBeforeChild = null;
assert(_currentlyUpdatingChildIndex == null);
try {
int firstIndex = _childElements.firstKey();
int lastIndex = _childElements.lastKey();
if (_childElements.isEmpty) {
firstIndex = 0;
lastIndex = 0;
} else if (_didUnderflow) {
lastIndex += 1;
}
for (int index = firstIndex; index <= lastIndex; ++index) {
void processElement(int index) {
_currentlyUpdatingChildIndex = index;
final Element newChild = updateChild(_childElements[index], _build(index), index);
if (newChild != null) {
_childElements[index] = newChild;
_currentBeforeChild = newChild.renderObject;
final SliverMultiBoxAdaptorParentData parentData = newChild.renderObject.parentData;
if (!parentData.keptAlive)
_currentBeforeChild = newChild.renderObject;
} else {
_childElements.remove(index);
}
}
// processElement may modify the Map - need to do a .toList() here.
_childElements.keys.toList().forEach(processElement);
if (_didUnderflow) {
final int lastKey = _childElements.lastKey() ?? -1;
processElement(lastKey + 1);
}
} finally {
_currentlyUpdatingChildIndex = null;
}

69
packages/flutter/test/material/tabs_test.dart
View File

@ -48,6 +48,23 @@ class StateMarkerState extends State<StateMarker> {
}
}
class AlwaysKeepAliveWidget extends StatefulWidget {
static String text = 'AlwaysKeepAlive';
@override
AlwaysKeepAliveState createState() => new AlwaysKeepAliveState();
}
class AlwaysKeepAliveState extends State<AlwaysKeepAliveWidget>
with AutomaticKeepAliveClientMixin {
@override
bool get wantKeepAlive => true;
@override
Widget build(BuildContext context) {
return new Text(AlwaysKeepAliveWidget.text);
}
}
Widget buildFrame({
Key tabBarKey,
List<String> tabs,
@ -1754,4 +1771,56 @@ void main() {
});
testWidgets('Skipping tabs with a KeepAlive child works', (WidgetTester tester) async {
// Regression test for https://github.com/flutter/flutter/issues/11895
final List<String> tabs = <String>[
'Tab1',
'Tab2',
'Tab3',
'Tab4',
'Tab5',
];
final TabController controller = new TabController(
vsync: const TestVSync(),
length: tabs.length,
);
await tester.pumpWidget(
new MaterialApp(
home: new Align(
alignment: Alignment.topLeft,
child: new SizedBox(
width: 300.0,
height: 200.0,
child: new Scaffold(
appBar: new AppBar(
title: const Text('tabs'),
bottom: new TabBar(
controller: controller,
tabs: tabs.map((String tab) => new Tab(text: tab)).toList(),
),
),
body: new TabBarView(
controller: controller,
children: <Widget>[
new AlwaysKeepAliveWidget(),
const Text('2'),
const Text('3'),
const Text('4'),
const Text('5'),
],
),
),
),
),
),
);
expect(find.text(AlwaysKeepAliveWidget.text), findsOneWidget);
expect(find.text('4'), findsNothing);
await tester.tap(find.text('Tab4'));
await tester.pumpAndSettle();
await tester.pump();
expect(controller.index, 3);
expect(find.text(AlwaysKeepAliveWidget.text, skipOffstage: false), findsOneWidget);
expect(find.text('4'), findsOneWidget);
});
}

38
packages/flutter/test/widgets/automatic_keep_alive_test.dart
View File

@ -496,6 +496,44 @@ void main() {
expect(find.text('FooBar 1'), findsNothing);
expect(find.text('FooBar 2'), findsNothing);
});
testWidgets('AutomaticKeepAlive with keepAlive set to true before initState and widget goes out of scope', (WidgetTester tester) async {
await tester.pumpWidget(new Directionality(
textDirection: TextDirection.ltr,
child: new ListView.builder(
itemCount: 250,
itemBuilder: (BuildContext context, int index){
if (index % 2 == 0){
return new _AlwaysKeepAlive(
key: GlobalObjectKey<_AlwaysKeepAliveState>(index),
);
}
return new Container(
height: 44.0,
child: new Text('FooBar $index'),
);
},
),
));
expect(find.text('keep me alive'), findsNWidgets(7));
expect(find.text('FooBar 1'), findsOneWidget);
expect(find.text('FooBar 3'), findsOneWidget);
expect(find.byKey(const GlobalObjectKey<_AlwaysKeepAliveState>(0)), findsOneWidget);
final ScrollableState state = tester.state(find.byType(Scrollable));
final ScrollPosition position = state.position;
position.jumpTo(3025.0);
await tester.pump();
expect(find.byKey(const GlobalObjectKey<_AlwaysKeepAliveState>(0), skipOffstage: false), findsOneWidget);
expect(find.text('keep me alive', skipOffstage: false), findsNWidgets(23));
expect(find.text('FooBar 1'), findsNothing);
expect(find.text('FooBar 3'), findsNothing);
expect(find.text('FooBar 73'), findsOneWidget);
});
}
class _AlwaysKeepAlive extends StatefulWidget {

109
packages/flutter/test/widgets/list_view_test.dart
View File

@ -18,6 +18,61 @@ class TestSliverChildListDelegate extends SliverChildListDelegate {
}
}
class Alive extends StatefulWidget {
const Alive(this.alive, this.index);
final bool alive;
final int index;
@override
AliveState createState() => new AliveState();
@override
String toString({DiagnosticLevel minLevel}) => '$index $alive';
}
class AliveState extends State<Alive> with AutomaticKeepAliveClientMixin {
@override
bool get wantKeepAlive => widget.alive;
@override
Widget build(BuildContext context) =>
new Text('${widget.index}:$wantKeepAlive');
}
typedef WhetherToKeepAlive = bool Function(int);
class _StatefulListView extends StatefulWidget {
const _StatefulListView(this.aliveCallback);
final WhetherToKeepAlive aliveCallback;
@override
_StatefulListViewState createState() => new _StatefulListViewState();
}
class _StatefulListViewState extends State<_StatefulListView> {
@override
Widget build(BuildContext context) {
return new GestureDetector(
// force a rebuild - the test(s) using this are verifying that the list is
// still correct after rebuild
onTap: () => setState,
child: new Directionality(
textDirection: TextDirection.ltr,
child: new ListView(
children: new List<Widget>.generate(200, (int i) {
return new Builder(
builder: (BuildContext context) {
return new Container(
child: new Alive(widget.aliveCallback(i), i),
);
},
);
}),
),
),
);
}
}
void main() {
testWidgets('ListView default control', (WidgetTester tester) async {
await tester.pumpWidget(
@ -91,7 +146,7 @@ void main() {
return new Container(
child: new Text('$i'),
);
}
},
);
}),
),
@ -120,6 +175,43 @@ void main() {
log.clear();
});
testWidgets('ListView large scroll jump and keepAlive first child not keepAlive', (WidgetTester tester) async {
Future<Null> checkAndScroll([String zero = '0:false']) async {
expect(find.text(zero), findsOneWidget);
expect(find.text('1:false'), findsOneWidget);
expect(find.text('2:false'), findsOneWidget);
expect(find.text('3:true'), findsOneWidget);
expect(find.text('116:false'), findsNothing);
final ScrollableState state = tester.state(find.byType(Scrollable));
final ScrollPosition position = state.position;
position.jumpTo(1025.0);
await tester.pump();
expect(find.text(zero), findsNothing);
expect(find.text('1:false'), findsNothing);
expect(find.text('2:false'), findsNothing);
expect(find.text('3:true', skipOffstage: false), findsOneWidget);
expect(find.text('116:false'), findsOneWidget);
await tester.tapAt(const Offset(100.0, 100.0));
position.jumpTo(0.0);
await tester.pump();
await tester.pump();
expect(find.text(zero), findsOneWidget);
expect(find.text('1:false'), findsOneWidget);
expect(find.text('2:false'), findsOneWidget);
expect(find.text('3:true'), findsOneWidget);
}
await tester.pumpWidget(new _StatefulListView((int i) => i > 2 && i % 3 == 0));
await checkAndScroll();
await tester.pumpWidget(new _StatefulListView((int i) => i % 3 == 0));
await checkAndScroll('0:true');
});
testWidgets('ListView can build out of underflow', (WidgetTester tester) async {
await tester.pumpWidget(
new Directionality(
@ -225,11 +317,14 @@ void main() {
testWidgets('didFinishLayout has correct indices', (WidgetTester tester) async {
final TestSliverChildListDelegate delegate = new TestSliverChildListDelegate(
new List<Widget>.generate(20, (int i) {
return new Container(
child: new Text('$i', textDirection: TextDirection.ltr),
);
})
new List<Widget>.generate(
20,
(int i) {
return new Container(
child: new Text('$i', textDirection: TextDirection.ltr),
);
},
)
);
await tester.pumpWidget(
@ -345,7 +440,7 @@ void main() {
),
),
),
);
);
expect(find.byType(Viewport), isNot(paints..clipRect()));
});