Pin sticky headers on top when adding slivers to a reverse CustomScrollView or ListView

Question

I am implementing a chat widget and using https://github.com/letsar/flutter_sticky_header library to separate messages by date, you can see the same behavior on Whatsapp and Telegram.

I am building several slivers that each contain messages on that date and a header which is basically a text showing the relevant date. I pass the slivers to a CustomScrollView with reverse property set to true.

 return CustomScrollView(
      slivers: _buildListItem(context, sectionIndex),
      reverse: true,
      controller: listScrollController,
    );

  List<Widget> _buildListItem(
    BuildContext context,
    List<ChatSection> chatSections,
  ) {
    List<Widget> slivers = List();
    chatSections.forEach((chatSection) {
      slivers.add(_buildChatSliver(
          context, chatSection.messages, chatSection.datetime));
    });

    return slivers;
  }

  SliverStickyHeaderBuilder _buildChatSliver(BuildContext context,
      List<ChatMessage> chatMessages, DateTime dateTimeHeader) {
    return SliverStickyHeaderBuilder(
      overlapsContent: false,
      builder: (context, state) {
        DateTime now = DateTime.now();
        String headerText = now.year != dateTimeHeader.year
            ? DateFormat("YYYY MMM dd").format(dateTimeHeader)
            : DateFormat("MMM dd").format(dateTimeHeader);
        return Container(
          padding: EdgeInsets.fromLTRB(5, 0, 15, 5),
          child: Center(
            child: Container(
              padding: EdgeInsets.fromLTRB(5, 5, 5, 5),
              decoration: BoxDecoration(
                  color: Color.fromARGB(200, 150, 150, 150),
                  borderRadius: BorderRadius.all(Radius.circular(5))),
              child: Text(
                headerText,
                style: TextStyle(
                    color: Colors.white70,
                    fontSize: 12.0,
                    fontStyle: FontStyle.italic),
              ),
            ),
          ),
        );
      },
      sliver: SliverList(
          delegate: SliverChildBuilderDelegate(
              (context, i) => _buildItem(chatMessages[i]),
              childCount: chatMessages.length)),
    );
  }

Everything works fine except that the headers are pinned to the bottom of the screen (I need them to stick to the top). How can I fix this? Any pointers would be appreciated.

Answer 1

Okay, I go my answer somewhere else and I am submitting it here for future reference:

try using different library (https://pub.dev/packages/sticky_headers).

return StickyHeader(
  header: _sectionHeader(dateText),
  content: Column(
    children: <Widget>[
      if (isLast) _topWidget(),
      for (var i in list.reversed)
        ListTile(
          title: ChatMessageWidget(
            message: i,
            senderUuid: widget.senderUuid,
            key: Key('chatmsg$key$i'),
            onLongPress: _onMsgPressed,
            onTap: _onMsgPressed,
          )
        )
    ]
  )
);

and then in build function:

return CustomScrollView(
  key: Key('MessagesList'),
  controller: _scrollController,
  slivers: <Widget>[
    SliverList(delegate: SliverChildBuilderDelegate((context, index) {
      if (index == 0) {
        return _bottomView();
      } else {
        final key = keys[index - 1];
        return _buildSection(context, key, mapped[key], index == keys.length);
      }
    },
    childCount: keys.length + 1)),
  ],
  reverse: true,
);

works well for me!