Flutter的FlexibleSpaceBar

1. FlexibleSpaceBar

// FlexibleSpaceBar
class FlexibleSpaceBarDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return NestedScrollView(
        headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
          return <Widget>[
            SliverAppBar(
              // 展开高度
              expandedHeight: 250.0,
              // 是否随着滑动隐藏标题
              floating: true,
              // 是否固定在顶部
              pinned: true,
              // 可折叠的应用栏目
              flexibleSpace: FlexibleSpaceBar(
                centerTitle: true,
                title: Text('可折叠的标题', style: TextStyle(color: Colors.white),),
                background: Image.network('https://ss0.bdstatic.com/70cFvHSh_Q1YnxGkpoWK1HF6hhy/it/u=2288748976,1582581638&fm=26&gp=0.jpg', fit: BoxFit.cover,),
              ),
            )
          ];
        },
        body: Center(
          child: Text('向上提拉，查看效果'),
        )
    );
  }
}

2. 图片展示