Fix nested scroll view can rebuild if mark dirty during scheduleWarmUpFrame (#36097)
diff --git a/packages/flutter/lib/src/widgets/nested_scroll_view.dart b/packages/flutter/lib/src/widgets/nested_scroll_view.dart
index 982596c..72b8878 100644
--- a/packages/flutter/lib/src/widgets/nested_scroll_view.dart
+++ b/packages/flutter/lib/src/widgets/nested_scroll_view.dart
@@ -498,8 +498,15 @@
bool get hasScrolledBody {
for (_NestedScrollPosition position in _innerPositions) {
- if (position.pixels > position.minScrollExtent)
+ // TODO(chunhtai): Replace null check with assert once
+ // https://github.com/flutter/flutter/issues/31195 is fixed.
+ if (
+ position.minScrollExtent != null &&
+ position.pixels != null &&
+ position.pixels > position.minScrollExtent
+ ) {
return true;
+ }
}
return false;
}
diff --git a/packages/flutter/test/widgets/nested_scroll_view_async_test.dart b/packages/flutter/test/widgets/nested_scroll_view_async_test.dart
new file mode 100644
index 0000000..075fc13
--- /dev/null
+++ b/packages/flutter/test/widgets/nested_scroll_view_async_test.dart
@@ -0,0 +1,72 @@
+// Copyright 2019 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/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/gestures.dart' show DragStartBehavior;
+import 'package:quiver/testing/async.dart';
+
+void main() {
+ setUp(() {
+ WidgetsFlutterBinding.ensureInitialized();
+ WidgetsBinding.instance.resetEpoch();
+ });
+
+ test('NestedScrollView can build sccessfully if mark dirty during warm up frame', () {
+ final FakeAsync fakeAsync = FakeAsync();
+ fakeAsync.run((FakeAsync async) {
+ runApp(
+ MaterialApp(
+ home: Material(
+ child: DefaultTabController(
+ length: 1,
+ child: NestedScrollView(
+ dragStartBehavior: DragStartBehavior.down,
+ headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
+ return <Widget>[
+ const SliverPersistentHeader(
+ delegate: TestHeader(),
+ ),
+ ];
+ },
+ body: SingleChildScrollView(
+ dragStartBehavior: DragStartBehavior.down,
+ child: Container(
+ height: 1000.0,
+ child: const Placeholder(),
+ ),
+ ),
+ ),
+ ),
+ ),
+ ),
+ );
+ // Marks element as dirty right before the first draw frame is called.
+ // This can happen when engine flush user setting.
+ final Element element = find.byType(NestedScrollView, skipOffstage: false).evaluate().single;
+ element.markNeedsBuild();
+ // Triggers draw frame timer scheduled in scheduleWarmUpFrame.
+ fakeAsync.flushTimers();
+ });
+ // Make sure widget is rebuilt correctly.
+ expect(
+ find.byType(NestedScrollView, skipOffstage: false).evaluate().single.widget is NestedScrollView,
+ isTrue
+ );
+ });
+}
+
+class TestHeader extends SliverPersistentHeaderDelegate {
+ const TestHeader();
+ @override
+ double get minExtent => 100.0;
+ @override
+ double get maxExtent => 100.0;
+ @override
+ Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) {
+ return const Placeholder();
+ }
+ @override
+ bool shouldRebuild(TestHeader oldDelegate) => false;
+}
