flutter - 内部列表视图达到顶部时如何最小化 DraggableScrollableSheet？

Question

我希望DraggableScrollableSheet当内部列表视图（里面的那个）到达顶部时开始最小化ItCrowdPage，我尝试将它包裹在下面，NotificationListener但它不起作用。

我试过的方法：-

NotificationListener<OverscrollNotification>(
                              onNotification: (value) {
                          

                                if (value.overscroll < 0 &&
                                    widget.scrollController.offset +
                                            value.overscroll <=
                                        0) {
                                  if (widget.scrollController.offset != 0)
                                    widget.scrollController.jumpTo(0);
                                } else if (widget.scrollController.offset +
                                        value.overscroll >=
                                    widget.scrollController.position
                                        .maxScrollExtent) {
                                  if (widget.scrollController.offset !=
                                      widget.scrollController.position
                                          .maxScrollExtent)
                                    widget.scrollController.jumpTo(widget
                                        .scrollController
                                        .position
                                        .maxScrollExtent);
                                }
                                widget.scrollController.jumpTo(
                                    widget.scrollController.position.pixels +
                                        value.overscroll);
                                return true;
                              },
                              child: ListView(
                                children: [
                                  Padding(
                                    padding:
                                        const EdgeInsets.only(bottom: 10.0),
                                    child: Text(
                                      listOfCharacters[index]['name'],
                                      textAlign: TextAlign.center,
                                      style: TextStyle(fontSize: 20),
                                    ),
                                  ),
                                  Container(
                                    color: cc[index],
                                    height: 50,
                                  ),
                                  Container(
                                    color: Colors.red,
                                    height: 500,
                                  )
                                ],
                              ),
                            );

完整代码片段：

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

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

/// This is the main application widget.
class MyApp extends StatelessWidget {
  const MyApp({Key key}) : super(key: key);

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: const MyStatelessWidget(),
      ),
    );
  }
}

class MyStatelessWidget extends StatelessWidget {
  const MyStatelessWidget({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Center(
        child: Stack(children: [
      DraggableScrollableSheet(
        initialChildSize: 0.6,
        minChildSize: 41 / MediaQuery.of(context).size.height,
        maxChildSize: 0.6,
        builder: (BuildContext context, ScrollController scrollController) {
          return ItCrowdPage(
            scrollController: scrollController,
          );
        },
      ),
    ]));
  }
}

class ClampScroll extends ScrollBehavior {
  @override
  Widget buildViewportChrome(
      BuildContext context, Widget child, AxisDirection axisDirection) {
    return child;
  }
}

class ItCrowdPage extends StatefulWidget {
  final ScrollController scrollController;

  const ItCrowdPage({Key key, @required this.scrollController})
      : super(key: key);
  @override
  _ItCrowdPageState createState() => _ItCrowdPageState();
}

class _ItCrowdPageState extends State<ItCrowdPage> {
  double viewPortFraction = 0.5;

  PageController pageController, pageController2;

  int currentPage = 0;

  List<Map<String, String>> listOfCharacters = [
    {'name': "Richmond"},
    {'name': "Roy"},
    {'name': "Moss"},
    {'name': "Douglas"},
    {'name': "Jen"}
  ];
  double page = 0.0;
  bool sc = false, sc2 = false;
  @override
  void initState() {
    pageController = PageController(
        initialPage: currentPage, viewportFraction: viewPortFraction);
    pageController2 = PageController(initialPage: currentPage);
    super.initState();
  }

  @override
  void dispose() {
    pageController.dispose();
    pageController2.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      clipBehavior: Clip.antiAlias,
      decoration: const BoxDecoration(
          color: Colors.pink,
          borderRadius: const BorderRadius.only(
              topLeft: Radius.circular(20), topRight: Radius.circular(20))),
      child: ScrollConfiguration(
        behavior: ClampScroll(),
        child: CustomScrollView(
          controller: widget.scrollController,
          slivers: [
            SliverFillRemaining(
              child: Column(
                children: [
                  Container(
                    margin: EdgeInsets.all(10),
                    width: 42,
                    height: 6,
                    decoration: BoxDecoration(
                        color: Colors.grey.shade300,
                        borderRadius:
                            const BorderRadius.all(Radius.circular(8))),
                  ),
                  // Expanded(
                  //     child: Container(
                  //   color: Colors.blueAccent,
                  // ))
                  const SizedBox(
                    height: 9,
                  ),
                  Flexible(
                    flex: 1,
                    fit: FlexFit.loose,
                    child: NotificationListener<ScrollNotification>(
                      onNotification: (ScrollNotification notification) {
                        if (notification is UserScrollNotification &&
                            sc == false) {
                          setState(() {
                            sc = true;
                            sc2 = false;
                          });
                          // print("i: ll");
                        } else if (notification is ScrollUpdateNotification) {
                          if (pageController2.page != pageController.page &&
                              sc) {
                            pageController2.position
                                .jumpTo(pageController.position.pixels * 2);
                          }
                          setState(() {
                            page = pageController.page;
                          });
                        }
                        return true;
                      },
                      child: PageView.builder(
                        onPageChanged: (pos) {
                          setState(() {
                            currentPage = pos;
                          });
                        },
                        physics: BouncingScrollPhysics(),
                        pageSnapping: sc,
                        controller: pageController,
                        itemCount: listOfCharacters.length,
                        itemBuilder: (context, index) {
                          return Container(
                            color: Colors.blueAccent,
                          );
                        },
                      ),
                    ),
                  ),
                  Flexible(
                    flex: 2,
                    child: NotificationListener<ScrollNotification>(
                      onNotification: (ScrollNotification notification) {
                        if (notification.depth == 0 &&
                            notification is UserScrollNotification &&
                            sc2 == false) {
                          setState(() {
                            // i = 2;
                            sc = false;
                            sc2 = true;
                          });
                          // print("i: ll");
                        } else if (notification.depth == 0 &&
                            notification is ScrollUpdateNotification &&
                            sc2) {
                          // page = pageController2;
                          if (pageController2.page != pageController.page) {
                            pageController.position
                                .jumpTo(pageController2.position.pixels / 2);
                          }
                        }
                        return true;
                      },
                      child: PageView.builder(
                        pageSnapping: sc2,
                        controller: pageController2,
                        onPageChanged: (pos) {
                          setState(() {
                            currentPage = pos;
                          });
                        },
                        physics: BouncingScrollPhysics(),
                        itemCount: listOfCharacters.length,
                        itemBuilder: (context, index) {
                          return ListView(
                            children: [
                              Padding(
                                padding: const EdgeInsets.only(bottom: 10.0),
                                child: Text(
                                  listOfCharacters[index]['name'],
                                  textAlign: TextAlign.center,
                                  style: TextStyle(fontSize: 20),
                                ),
                              ),
                              Container(
                                color: cc[index],
                                height: 50,
                              ),
                              Container(
                                color: Colors.red,
                                height: 500,
                              )
                            ],
                          );
                        },
                      ),
                    ),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}

const List<Color> cc = [
  Colors.black,
  Colors.green,
  Colors.purple,
  Colors.yellow,
  Colors.blueAccent
];