LoadingMoreCustomScrollView add center attribute

[mdddj]

CustomScrollView has Key? center attribute, please add this, tkx

use center eg.

///聊天内容展示
  Widget get chatsListWidget {
    return LoadingMoreCustomScrollView(
      reverse: true,
      controller: scroller,
      center: // <<< - todo add a center key
      slivers: [
        LoadingMoreSliverList(SliverListConfig<ChatItemData>(
          itemBuilder:renderChatLayoutItem,
          sourceList: repository,
          indicatorBuilder: (s, c) => kBuildIndicator(s, c, isSliver: true),
          extendedListDelegate: const ExtendedListDelegate(closeToTrailing: true),
          showNoMore: false
        )),
        SliverPadding(
          padding: EdgeInsets.zero,
          key: centerKey,
        ),
        LoadingMoreSliverList(SliverListConfig<ChatItemData>(
          itemBuilder: renderChatLayoutItem,
          sourceList: repositoryNew,
          showNoMore: false,
        ))
      ],
    );
  }

  ///旧版本
  Widget get oldVersion {
    return CustomScrollView(
      controller: scroller,
      center: centerKey,
      slivers: [
        // ChatUserDetailCard(model.txModel!.conversationID).toSliverWidget,
        //旧的聊天记录
        SliverPadding(
          padding: EdgeInsets.zero,
          key: centerKey,
        ),
        //新的聊天记录
        const Chats(),
      ],
    );
  }