Flutter:无法使用 TabBar 设置 SliverPersistentHeader 的首选高度

Question

我正在尝试制作我的 TabBar高度有点大。它仅适用于特定值。这是我的 SliverPersistentHeader :

SliverPersistentHeader(
  pinned: true,
  delegate: _SliverAppBarTabDelegate(
    child: PreferredSize(
      preferredSize: Size.fromHeight(45.0),
      child: Container(
        color: Colors.white,
        child: TabBar(
          isScrollable: true,
          labelColor: Colors.black,
          unselectedLabelColor: Colors.black38,
          indicatorColor: Theme.of(context).primaryColor,
          tabs: createTabList(),
          controller: tabBarController,
        ),
      ),
    ),
  ),
),

这是我的代表:

class _SliverAppBarTabDelegate extends SliverPersistentHeaderDelegate {
  final PreferredSize child;

  _SliverAppBarTabDelegate({this.child});

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

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

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

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

为什么它不允许我将大小设置为更大的值？
编辑:
这是我的有状态小部件的整体结构:

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: CustomScrollView(
      slivers: <Widget>[
        SliverAppBar(),
        SliverPersistentHeader(),
        SliverList(),
      ],
    ),
  );
}

Answer 1

包裹 _SliverAppBarTabDelegate的 child 带着 SizedBox.expand :

class _SliverAppBarTabDelegate extends SliverPersistentHeaderDelegate {
  final PreferredSize child;

  _SliverAppBarTabDelegate({this.child});

  @override
  Widget build(
      BuildContext context, double shrinkOffset, bool overlapsContent) {
    return SizedBox.expand(child: child);
  }

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

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

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