tabbed_scrollview_warp_test.dart 2.42 KB
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// Copyright 2014 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

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// @dart = 2.8

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import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/material.dart';

// This is a regression test for https://github.com/flutter/flutter/issues/10549
// which was failing because _SliverPersistentHeaderElement.visitChildren()
// didn't check child != null before visiting its child.

class MySliverPersistentHeaderDelegate extends SliverPersistentHeaderDelegate {
  @override
  double get minExtent => 50.0;

  @override
  double get maxExtent => 150.0;

  @override
  Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) => const Placeholder(color: Colors.teal);

  @override
  bool shouldRebuild(covariant SliverPersistentHeaderDelegate oldDelegate) => false;
}

class MyHomePage extends StatefulWidget {
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  const MyHomePage({ Key key }) : super(key: key);

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  @override
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  _MyHomePageState createState() => _MyHomePageState();
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}

class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
  static const int tabCount = 3;
  TabController tabController;

  @override
  void initState() {
    super.initState();
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    tabController = TabController(initialIndex: 0, length: tabCount, vsync: this);
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  }

  @override
  void dispose() {
    tabController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
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    return Scaffold(
      appBar: AppBar(
        bottom: TabBar(
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          controller: tabController,
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          tabs: List<Widget>.generate(tabCount, (int index) => Tab(text: 'Tab $index')).toList(),
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        ),
      ),
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      body: TabBarView(
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        controller: tabController,
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        children: List<Widget>.generate(tabCount, (int index) {
          return CustomScrollView(
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            // The bug only occurs when this key is included
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            key: ValueKey<String>('Page $index'),
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            slivers: <Widget>[
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              SliverPersistentHeader(
                delegate: MySliverPersistentHeaderDelegate(),
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              ),
            ],
          );
        }).toList(),
      ),
    );
  }
}

void main() {
  testWidgets('Tabbed CustomScrollViews, warp from tab 1 to 3', (WidgetTester tester) async {
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    await tester.pumpWidget(const MaterialApp(home: MyHomePage()));
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    // should not crash.
    await tester.tap(find.text('Tab 2'));
    await tester.pumpAndSettle();
  });
}