Flutter 中的标准底部 Sheet

Question

我很难在我的应用程序中实现 "Standard Bottom Sheet" - 我的意思是底部 sheet 其中 "header" 可见且可拖动（参考：https://material.io/design/components/sheets-bottom.html#standard-bottom-sheet).甚至更多：我找不到它的任何例子 anywhere:S。我想要的结果是通过将 DraggableScrollableSheet 实现为 bottomSheet: in Scaffold （只有那个小部件有 initialChildSize) 但接缝就像没有办法制作 header "sticky" 因为所有内容都是可滚动的：/.

我还发现了这个：https://flutterdoc.com/bottom-sheets-in-flutter-ec05c90453e7 - 接缝就像那里关于 "Persistent Bottom Sheet" 的部分是我正在寻找的那个，但文章并不详细，所以我无法完全弄清楚实施它加上那里的评论很消极所以我猜它不完全正确...

有没有人有解决办法？:S

Answer 1

如果您正在寻找 Persistent Bottomsheet，请参考下面的源代码 link

Persistent Bottomsheet

您可以参考 _showBottomSheet() 来满足您的要求，一些更改将满足您的要求

Answer 2

您可以使用堆栈和动画来实现：


class HelloWorldPage extends StatefulWidget {
  @override
  _HelloWorldPageState createState() => _HelloWorldPageState();
}

class _HelloWorldPageState extends State<HelloWorldPage>
    with SingleTickerProviderStateMixin {
  final double minSize = 80;
  final double maxSize = 350;

  void initState() {
    _controller =
        AnimationController(vsync: this, duration: Duration(milliseconds: 500))
          ..addListener(() {
            setState(() {});
          });

    _animation =
        Tween<double>(begin: minSize, end: maxSize).animate(_controller);

    super.initState();
  }

  AnimationController _controller;
  Animation<double> _animation;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        fit: StackFit.expand,
        children: <Widget>[
          Positioned(
            bottom: 0,
            height: _animation.value,
            child: GestureDetector(
              onDoubleTap: () => _onEvent(),
              onVerticalDragEnd: (event) => _onEvent(),
              child: Container(
                color: Colors.red,
                width: MediaQuery.of(context).size.width,
                height: minSize,
              ),
            ),
          ),
        ],
      ),
    );
  }

  _onEvent() {
    if (_controller.isCompleted) {
      _controller.reverse(from: maxSize);
    } else {
      _controller.forward();
    }
  }

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

Answer 3

由于@Sergio 命名了一些好的替代方案，它仍然需要更多编码才能使其正常工作，我发现 Sliding_up_panel 所以对于其他人来说解决方案你可以找到它 here .

不过，我发现 Flutter 中内置的 bottomSheet 小部件没有提供创建 material.io 中提到的 "standard bottom sheet" 的选项真的很奇怪 :S

Answer 4

您可以在 material 规范中看到的标准底部 sheet 行为可以使用 DraggableScrollableSheet.

实现

下面我来详细解释一下。

第 1 步：

定义你的Scaffold.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Draggable sheet demo',
      home: Scaffold(

          ///just for status bar color.
          appBar: PreferredSize(
              preferredSize: Size.fromHeight(0),
              child: AppBar(
                primary: true,
                elevation: 0,
              )),
          body: Stack(
            children: <Widget>[
              Positioned(
                left: 0.0,
                top: 0.0,
                right: 0.0,
                child: PreferredSize(
                    preferredSize: Size.fromHeight(56.0),
                    child: AppBar(
                      title: Text("Standard bottom sheet demo"),
                      elevation: 2.0,
                    )),
              ),
              DraggableSearchableListView(),
            ],
          )),
    );
  }
}

第 2 步：

定义DraggableSearchableListView

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

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

class _DraggableSearchableListViewState
    extends State<DraggableSearchableListView> {
  final TextEditingController searchTextController = TextEditingController();
  final ValueNotifier<bool> searchTextCloseButtonVisibility =
      ValueNotifier<bool>(false);
  final ValueNotifier<bool> searchFieldVisibility = ValueNotifier<bool>(false);
  @override
  void dispose() {
    searchTextController.dispose();
    searchTextCloseButtonVisibility.dispose();
    searchFieldVisibility.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return NotificationListener<DraggableScrollableNotification>(
      onNotification: (notification) {
        if (notification.extent == 1.0) {
          searchFieldVisibility.value = true;
        } else {
          searchFieldVisibility.value = false;
        }
        return true;
      },
      child: DraggableScrollableActuator(
        child: Stack(
          children: <Widget>[
            DraggableScrollableSheet(
              initialChildSize: 0.30,
              minChildSize: 0.15,
              maxChildSize: 1.0,
              builder:
                  (BuildContext context, ScrollController scrollController) {
                return Container(
                  decoration: BoxDecoration(
                    color: Colors.white,
                    borderRadius: BorderRadius.only(
                      topLeft: Radius.circular(16.0),
                      topRight: Radius.circular(16.0),
                    ),
                    boxShadow: [
                      BoxShadow(
                          color: Colors.grey,
                          offset: Offset(1.0, -2.0),
                          blurRadius: 4.0,
                          spreadRadius: 2.0)
                    ],
                  ),
                  child: ListView.builder(
                    controller: scrollController,

                    ///we have 25 rows plus one header row.  
                    itemCount: 25 + 1,
                    itemBuilder: (BuildContext context, int index) {
                      if (index == 0) {
                        return Container(
                          child: Column(
                            children: <Widget>[
                              Align(
                                alignment: Alignment.centerLeft,
                                child: Padding(
                                  padding: EdgeInsets.only(
                                    top: 16.0,
                                    left: 24.0,
                                    right: 24.0,
                                  ),
                                  child: Text(
                                    "Favorites",
                                    style:
                                        Theme.of(context).textTheme.headline6,
                                  ),
                                ),
                              ),
                              SizedBox(
                                height: 8.0,
                              ),
                              Divider(color: Colors.grey),
                            ],
                          ),
                        );
                      }
                      return Padding(
                          padding: EdgeInsets.symmetric(horizontal: 16.0),
                          child: ListTile(title: Text('Item $index')));
                    },
                  ),
                );
              },
            ),
            Positioned(
              left: 0.0,
              top: 0.0,
              right: 0.0,
              child: ValueListenableBuilder<bool>(
                  valueListenable: searchFieldVisibility,
                  builder: (context, value, child) {
                    return value
                        ? PreferredSize(
                            preferredSize: Size.fromHeight(56.0),
                            child: Container(
                              decoration: BoxDecoration(
                                border: Border(
                                  bottom: BorderSide(
                                      width: 1.0,
                                      color: Theme.of(context).dividerColor),
                                ),
                                color: Theme.of(context).colorScheme.surface,
                              ),
                              child: SearchBar(
                                closeButtonVisibility:
                                    searchTextCloseButtonVisibility,
                                textEditingController: searchTextController,
                                onClose: () {
                                  searchFieldVisibility.value = false;
                                  DraggableScrollableActuator.reset(context);
                                },
                                onSearchSubmit: (String value) {
                                  ///submit search query to your business logic component
                                },
                              ),
                            ),
                          )
                        : Container();
                  }),
            ),
          ],
        ),
      ),
    );
  }
}

第 3 步：

定义自定义粘性搜索栏

 class SearchBar extends StatelessWidget {
  final TextEditingController textEditingController;
  final ValueNotifier<bool> closeButtonVisibility;
  final ValueChanged<String> onSearchSubmit;
  final VoidCallback onClose;

  const SearchBar({
    Key key,
    @required this.textEditingController,
    @required this.closeButtonVisibility,
    @required this.onSearchSubmit,
    @required this.onClose,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = Theme.of(context);
    return Container(
      child: Padding(
        padding: EdgeInsets.symmetric(horizontal: 0),
        child: Row(
          children: <Widget>[
            SizedBox(
              height: 56.0,
              width: 56.0,
              child: Material(
                type: MaterialType.transparency,
                child: InkWell(
                  child: Icon(
                    Icons.arrow_back,
                    color: theme.textTheme.caption.color,
                  ),
                  onTap: () {
                    FocusScope.of(context).unfocus();
                    textEditingController.clear();
                    closeButtonVisibility.value = false;
                    onClose();
                  },
                ),
              ),
            ),
            SizedBox(
              width: 16.0,
            ),
            Expanded(
              child: TextFormField(
                onChanged: (value) {
                  if (value != null && value.length > 0) {
                    closeButtonVisibility.value = true;
                  } else {
                    closeButtonVisibility.value = false;
                  }
                },
                onFieldSubmitted: (value) {
                  FocusScope.of(context).unfocus();
                  onSearchSubmit(value);
                },
                keyboardType: TextInputType.text,
                textInputAction: TextInputAction.search,
                textCapitalization: TextCapitalization.none,
                textAlignVertical: TextAlignVertical.center,
                textAlign: TextAlign.left,
                maxLines: 1,
                controller: textEditingController,
                decoration: InputDecoration(
                  isDense: true,
                  border: InputBorder.none,
                  hintText: "Search here",
                ),
              ),
            ),
            ValueListenableBuilder<bool>(
                valueListenable: closeButtonVisibility,
                builder: (context, value, child) {
                  return value
                      ? SizedBox(
                          width: 56.0,
                          height: 56.0,
                          child: Material(
                            type: MaterialType.transparency,
                            child: InkWell(
                              child: Icon(
                                Icons.close,
                                color: theme.textTheme.caption.color,
                              ),
                              onTap: () {
                                closeButtonVisibility.value = false;
                                textEditingController.clear();
                              },
                            ),
                          ),
                        )
                      : Container();
                })
          ],
        ),
      ),
    );
  }
}

查看最终输出的屏幕截图。

状态 1:

底部 sheet 以其初始大小显示。

状态2：

用户向上拖动底部 sheet。

状态 3:

底部 sheet 到达屏幕的顶部边缘，显示粘性自定义 SearchBar 界面。

就这些了。

查看现场演示 here。

Answer 5

可以用 showModalBottomSheet 轻松实现。代码：

void _presentBottomSheet(BuildContext context) {
  showModalBottomSheet(
    context: context,
    builder: (context) => Wrap(
      children: <Widget>[
        SizedBox(height: 8),
        _buildBottomSheetRow(context, Icons.share, 'Share'),
        _buildBottomSheetRow(context, Icons.link, 'Get link'),
        _buildBottomSheetRow(context, Icons.edit, 'Edit Name'),
        _buildBottomSheetRow(context, Icons.delete, 'Delete collection'),
      ],
    ),
  );
}

Widget _buildBottomSheetRow(
  BuildContext context,
  IconData icon,
  String text,
) =>
    InkWell(
      onTap: () {},
      child: Row(
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(16),
            child: Icon(
              icon,
              color: Colors.grey[700],
            ),
          ),
          SizedBox(width: 8),
          Text(text),
        ],
      ),
    );

Flutter 中的标准底部 Sheet

Standard Bottom Sheet in Flutter

flutter

bottom-sheet

第 1 步：

第 2 步：

第 3 步：

查看最终输出的屏幕截图。