传递 scrollController 时 CustomScrollView 滚动行为发生变化

Question

我正在尝试自动滚动到 SliverList 的末尾，它位于 CustomScrollView 中。 SliverList 本身没有控制器属性，所以我必须将 ScrollController 传递给 CustomScrollView。

问题是当我将控制器传递给CustomScrollView 时，它的行为发生了变化，它不再滚动外部列表，也不会导致SliverAppBar 小部件折叠。如何自动滚动 SliverList 并保持 CustomScrollView 的行为与以前一样？

这是我的代码：

class _MyHomePageState extends State<MyHomePage> {
  ScrollController _scrollController = ScrollController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () {
            _scrollController.animateTo(
              _scrollController.position.maxScrollExtent,
              curve: Curves.easeOut,
              duration: const Duration(seconds: 1),
            );
          },
        ),
        body: NestedScrollView(
          headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
            return <Widget>[
              SliverAppBar(
                expandedHeight: 230.0,
                pinned: true,
                flexibleSpace: FlexibleSpaceBar(
                  title: Text('SliverAppBar Expand'),
                ),
              )
            ];
          },
          body: CustomScrollView(
                //When controller is passed to CustomScrollView, its behavior changes
                // controller: _scrollController,  
                slivers: [
                  //Some widgets are here
                  SliverList(
                    delegate: SliverChildBuilderDelegate(
                      (context, index) {
                        return Container(
                          height: 80,
                          color: Colors.primaries[index % Colors.primaries.length],
                          alignment: Alignment.center,
                          child: Text(
                            'Item : $index',
                          ),
                        );
                      },
                      childCount: 20,
                    ),
                  ),
                ],
              ),
            ) ,
         );
      }
    }

Answer 1

我想你可能会注意到这里对示例的解释：NestedScrollView class

// The "controller" and "primary" members should be left
// unset, so that the NestedScrollView can control this
// inner scroll view.
// If the "controller" property is set, then this scroll
// view will not be associated with the NestedScrollView.
// The PageStorageKey should be unique to this ScrollView;
// it allows the list to remember its scroll position when
// the tab view is not on the screen.

和

// This Builder is needed to provide a BuildContext that is
// "inside" the NestedScrollView, so that
// sliverOverlapAbsorberHandleFor() can find the
// NestedScrollView.

正确的方法是获取CustomScrollView使用的控制器，而不是添加新的。

可以通过在CustomScrollView上方添加Builder来完成）并将控制器分配给_scrollController。

...
  body: NestedScrollView(
    ...
    body: Builder(
      builder: (context){
        _scrollController = PrimaryScrollController.of(context);
        return CustomScrollView(
          ...
      },
    ),
  ),
...