testing - Flutter:如何测试滚动

Question

我有一个带有 ScrollController 作为 Controller 的 ListView.builder:

  _buildListView(state) => ListView.builder(
        itemBuilder: (_, int index) => _draw(index, state),
        itemCount: state.count
        controller: _scrollController,
      );

我向 Controller 添加一个监听器:

  View() {
    _scrollController.addListener(_onScroll);
  }

我想测试 _onScroll 函数:

 void _onScroll() {
    final maxScroll = _scrollController.position.maxScrollExtent;
    final currentScroll = _scrollController.position.pixels;
    if (maxScroll - currentScroll <= _scrollThreshold) {
      _bloc.dispatch(Fetch());
    }
  }

但我不知道如何测试它。到目前为止，这是我尝试过的:

  testWidgets('Should test the scroll',
      (WidgetTester tester) async {
await tester.pumpWidget(generateApp());
    await tester.pump();
    await tester.drag(find.byType(ListView), const Offset(0.0, -300));
    await tester.pump();
...

)}

但它根本不调用该函数。

Answer 1

对于那些使用新的 flutter_test 库的用户，我们还有 dragUntilVisible 方法:

await tester.dragUntilVisible(
    find.text('Earn mana!'), // what you want to find
    find.byKey(ValueKey('OnboardingCarousel')), // widget you want to scroll
    const Offset(-250, 0), // delta to move
);