带有 SliverAppBar 的 ScrollablePositionedList 无法正常工作

Question

This is a repository 创建一个最小的可重现示例。

我想在滚动 ScrollablePositionedList.builder 时隐藏 SliverAppBar。这是我在此处包含的相关代码。

          NestedScrollView(
              headerSliverBuilder: (context, innerBoxIsScrolled) => [
                    SliverAppBar(
                      backgroundColor: Colors.blue,
                      expandedHeight: 112,
                      snap: true,
                      pinned: false,
                      floating: true,
                      forceElevated: true,
                      actions: <Widget>[
                        IconButton(
                          icon: Icon(Icons.event),
                        )
                      ],
                      flexibleSpace: SafeArea(
                        child: Column(
                          children: <Widget>[
                            Container(
                              height: kToolbarHeight,
                              child: Column(
                                crossAxisAlignment: CrossAxisAlignment.center,
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  Text(
                                    'Title',
                                    style: Theme.of(context)
                                        .textTheme
                                        .title
                                        .copyWith(
                                            fontSize: 16, color: Colors.white),
                                  ),
                                  SizedBox(
                                    height: 2,
                                  ),
                                  Text(
                                    'Date',
                                    style: Theme.of(context)
                                        .textTheme
                                        .caption
                                        .copyWith(
                                            fontSize: 10, color: Colors.white),
                                  ),
                                  SizedBox(
                                    height: 2,
                                  ),
                                  Text(
                                    'Another Text',
                                    style: Theme.of(context)
                                        .textTheme
                                        .subtitle
                                        .copyWith(
                                            fontSize: 14, color: Colors.white),
                                  ),
                                ],
                              ),
                            ),
                            Expanded(
                              child: Container(
                                height: kToolbarHeight,
                                width: MediaQuery.of(context).size.width,
                                color: Colors.white,
                                child: Row(
                                  mainAxisAlignment:
                                      MainAxisAlignment.spaceEvenly,
                                  children: <Widget>[
                                    Text(
                                      'Prev',
                                    ),
                                    Text(
                                      'Next',
                                    )
                                  ],
                                ),
                              ),
                            )
                          ],
                        ),
                      ),
                    )
                  ],
              body: ScrollablePositionedList.builder(
                  physics: ScrollPhysics(),
                  itemPositionsListener: itemPositionListener,
                  itemScrollController: _itemScrollController,
                  initialScrollIndex: 0,
                  itemCount: 500,
                  itemBuilder: (BuildContext ctxt, int index) {
                    return Container(
                        margin: EdgeInsets.all(16)
                        ,
                        child: Text('$index'));
                  })),

到目前为止，我尝试了两种方法 none，其中的方法工作正常，

方法一

I added physics: ScrollPhysics(), to ScrollablePositionedList.builder

输出：

方法 2

I added physics: NeverScrollableScrollPhysics(), to ScrollablePositionedList.builder

SliverAppBar 这次隐藏了，但现在我无法滚动到 ScrollablePositionedList.builder 的末尾我的列表中有 500 个项目，但它只能滚动到第 14 个项目，查看输出。此外，它在滚动时滞后太多

输出：

提前致谢。

Answer 1

自己回答问题

This problem has no solution for it. I have created an issue here

看起来 ScrollablePositionedList 和 SliverAppBar 无法工作，直到 Flutter Team 不添加 shrinkwrap 属性到 ScrollablePositionedList.

添加 shrinkwrap 的功能请求已创建 here

Answer 2

    It works for me
    //create list of global keys

     List<GlobalKey> _formKeys = [];
    
    
    //assign keys from your list
    
    for(int i=0 ;i< syourlist.length;i++){
    final key = GlobalKey();
    _formKeys.add(key);
    }
    
    //in list view give key as below
    
    key:_formKeys[index]
    
    
    //on button click
    
     Scrollable.ensureVisible(_formKeys[index].currentContext);

Answer 3

这是一个基本的解决方法：

使用 ItemsPositionsListener 侦听列表滚动到的当前项目。
然后创建布尔值来检查 scroll-direction 和金额。
这些条件控制一个控制自定义高度的 AnimatedContainer header。
它作为 child 放置在具有 header 的列中，因此可滚动列表在动画前后正确占据 space。

虽然这是非常基础的，没有使用 NestedScrollView，但它仍然使用 ScrollablePositionedList，并根据设置的滚动条件实现与滑入和滑出的 header 类似的效果。

以防万一帮助其他人，直到根本问题得到解决...:)


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

class ScrollAllWords extends StatefulWidget {
  const ScrollAllWords({
    Key? key,
    required this.list,
  }) : super(key: key);

  final List<String> list;

  @override
  State<ScrollAllWords> createState() => _ScrollAllWordsState();
}

class _ScrollAllWordsState extends State<ScrollAllWords> {

/// use this listener to control the header position.
  final _itemPositionsListener = ItemPositionsListener.create();

///Can also use the ItemScrollController to animate through the list (code omitted)
final _itemScrollController = ItemScrollController();


  /// Gets the current index the list has scrolled to.
  int _currentIndex = 0;

  /// Compares against current index to determine the scroll direction.
  int _shadowIndex = 0;


  bool _reverseScrolling = false;
  bool _showHeader = true;

  @override
  void initState() {

    /// Set up the listener.
    _itemPositionsListener.itemPositions.addListener(() {
      checkScroll();
    });

    super.initState();
  }

  void checkScroll() {
    /// Gets the current index of the scroll.
    _currentIndex =
        _itemPositionsListener.itemPositions.value
            .elementAt(0)
            .index;

    /// Checks the scroll direction.
    if (_currentIndex > _shadowIndex) {
      _reverseScrolling = false;
      _shadowIndex = _currentIndex;
    }
    if (_currentIndex < _shadowIndex) {
      _reverseScrolling = true;
      _shadowIndex = _currentIndex;
    }

    /// Checks whether to show or hide the scroller (e.g. show when scrolled passed 15 items and not reversing).
    if (!_reverseScrolling && _currentIndex > 15) {
      _showHeader = false;
    } else {
      _showHeader = true;
    }

    setState(() {});
  }

  @override
  Widget build(BuildContext context) {

    return Column(
      children: [
        AnimatedContainer(
          duration: const Duration(milliseconds: 120),
          height: _showHeader ? 200 : 0,
          curve: Curves.easeOutCubic,

          child: Container(
            color: Colors.red,
            height: size.height * 0.20,
          ),
        ),

        Flexible(
          child: ScrollablePositionedList.builder(
            itemScrollController: _itemScrollController,
            itemPositionsListener: _itemPositionsListener,
            itemCount: widget.list.length,
            itemBuilder: (context, index) {
              return ListTile(
                title: Text(widget.list[index]),
              );
            },
          ),
        ),

      ],
    );
  }
}

带有 SliverAppBar 的 ScrollablePositionedList 无法正常工作

ScrollablePositionedList with SliverAppBar not working properly

flutter

flutter-layout

nestedscrollview

scroll-position

sliverappbar

方法一

方法 2