flutter - Sliverappbar に本文のコンテンツが重なる (Flutter)

Question

より良いUIのためにスライバーアプリバーを使用しています。ピン留めする必要があるアプリバー内にタブを保持したかったのです。タブのみを固定する必要があり、タイトル付きのアプリ バーは上部にドラッグするだけで展開する必要があります。trueに固定したままにすると、タブが本文の不要なコンテンツに重なってしまいます。

  return Scaffold(
      body: SafeArea(
        child: DefaultTabController(
          length: 5,
          child: NestedScrollView(
            headerSliverBuilder:
                (BuildContext context, bool innerBoxIsScrolled) {
              return <Widget>[
                SliverAppBar(

                  backgroundColor: Colors.white,
                  floating: false,
                  flexibleSpace: FlexibleSpaceBar(
                    title: Text(
                      "Home Page",
                      style: TextStyle(
                        color: Colors.teal,
                      ),
                    ),
                  ),
                  actions: [
                    IconButton(
                      icon: Icon(
                        Icons.message,
                        color: Colors.grey[700],
                      ),
                      onPressed: () {},
                    ),
                    SizedBox(width: 5)

                  ],

                ),
                SliverPersistentHeader(
                  pinned: true,
                  delegate: _SliverAppBarDelegate(
                    TabBar(
                      labelColor: Colors.teal,
                      unselectedLabelColor: Colors.grey[600],
                      tabs: [
                        Tab(icon: Icon(Icons.home)),
                        Tab(icon: Icon(Icons.people_outline)),
                        Tab(icon: Icon(Icons.account_balance)),
                        Tab(icon: Icon(Icons.notifications_active)),
                        Tab(icon: Icon(Icons.menu)),
                      ],
                    ),
                  ),
                ),
              ];
            },
            body: ListView(
              children: [
                Column(
                  children: [
                    Padding(
                      padding: const EdgeInsets.symmetric(vertical: 10.0),
                      child: Row(
                        children: [
                          SizedBox(width: 10),
                          Padding(
                            padding: const EdgeInsets.symmetric(horizontal: 6.0),
                            child: CircleAvatar(
                              radius: width(context) * 0.08,
                            ),
                          ),
                          Padding(
                            padding: const EdgeInsets.symmetric(horizontal: 4.0),
                            child: Container(
                              width: width(context) * 0.74,
                              height: width(context) * 0.15,
                              decoration: BoxDecoration(
                                  border: Border.all(color: Colors.grey[800]),
                                  borderRadius: BorderRadius.circular(100)),
                              child: Column([![enter image description here][1]][1]
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: [
                                  Wrap(
                                    children: [
                                      Text('To ask a question \n type here...', style: TextStyle(fontSize: 22),),
                                    ],
                                  ),

                                ],
                              ),
                            ),
                          ),
                        ],
                      ),
                    ),
                    Row(
                      children: [
                        Padding(
                          padding: const EdgeInsets.all(8.0),
                          child: Container(
                            height: height(context)*0.07,
                            width: width(context)*0.70,
                            decoration: BoxDecoration(
                                border: Border.all(color: Colors.grey[800]),
                                borderRadius: BorderRadius.circular(10)),
                          ),
                        ),
                        Container(
                          height: height(context)*0.07,
                          width: width(context)*0.25,
                          decoration: BoxDecoration(
                              border: Border.all(color: Colors.grey[800]),
                              borderRadius: BorderRadius.circular(10)),
                        ),
                      ],
                    ),
                    Padding(
                      padding: const EdgeInsets.only(top: 8.0, left: 8, right: 8),
                      child: Divider(
                        color: Colors.grey[600],
                      ),
                    ),
                    Padding(
                      padding: const EdgeInsets.only(top: 8.0, left: 8, right: 8),
                      child: Card(
                        child: Container(
                          height: 200,
                        ),
                      ),
                    ),
                    Padding(
                      padding: const EdgeInsets.only(top: 8.0, left: 8, right: 8),
                      child: Card(
                        child: Container(
                          height: 200,
                        ),
                      ),
                    ),
                    Padding(
                      padding: const EdgeInsets.only(top: 8.0, left: 8, right: 8),
                      child: Card(
                        child: Container(
                          height: 200,
                        ),
                      ),
                    ), Padding(
                      padding: const EdgeInsets.only(top: 8.0, left: 8, right: 8),
                      child: Card(
                        child: Container(
                          height: 200,
                        ),
                      ),
                    ),


                  ],
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

class _SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
  _SliverAppBarDelegate(this._tabBar);

  final TabBar _tabBar;

  @override
  double get minExtent => _tabBar.preferredSize.height;

  @override
  double get maxExtent => _tabBar.preferredSize.height;

  @override
  Widget build(
      BuildContext context, double shrinkOffset, bool overlapsContent) {
    return new Container(
      child: _tabBar,
    );
  }

  @override
  bool shouldRebuild(_SliverAppBarDelegate oldDelegate) {
    return false;
  }
}