flutter - 如何让我的 appbar 在灵活的 app bar 的同时充当 Material 搜索小部件

Question

我希望我的应用栏在向下滚动或用户搜索内容时充当固定的应用栏。

SliverAppBar(
  title: new TextField(
    style: Theme.of(context).primaryTextTheme.title,
    decoration: InputDecoration(
      hintText: '검색',
    ),
  ),
),

---

但我想在向上滚动且用户未搜索时将其绘制为灵活的应用栏。

flexibleSpace: new FlexibleSpaceBar(
  centerTitle: false,
  title: new TextField(
    style: Theme.of(context).primaryTextTheme.title,
    decoration: InputDecoration(
      hintText: '검색',
    ),
  ),
  background: Stack(
    fit: StackFit.expand,
    children: <Widget>[
      SizedBox(
        height: 256.0,
        child: Container(
          child: Padding(
            padding: const EdgeInsets.only(top: 24.0),
            child: Column(
              children: <Widget>[
                Align(
                  alignment: Alignment.topLeft,
                  child: FlutterLogo(
                    size: 64.0,
                  ),
                ),
                Padding(padding: const EdgeInsets.only(bottom: 24.0)),
                ListTile(
                  title: Text('Some Text'),
                ),
              ],
            ),
          ),
        ),
      ),
      // This gradient ensures that the toolbar icons are distinct
      // against the background image.
    ],
  ),
),

当使用第二种方法向上滚动时，搜索字段会转换到右上角。

Answer 1

将title内容移动到另一个SliverList中可以达到效果。

从 SliverAppBar 中移除 flexibleSpace，并将 flexibleSpace.background 的内容移动到 SliverList 之前 SliverAppBar。

例子:

@override
Widget build(BuildContext context) {
  return new CustomScrollView(
    slivers: <Widget>[
      new SliverList(
          delegate: new SliverChildListDelegate(<Widget>[
        Align(
          alignment: Alignment.topLeft,
          child: FlutterLogo(size: 64.0),
        ),
        ListTile(
          title: Text('Some Text'),
        ),
        ListTile(),
      ])),
      new SliverAppBar(
        backgroundColor: Theme.of(context).scaffoldBackgroundColor,
        elevation: 0.0,
        automaticallyImplyLeading: false,
        pinned: true,
        floating: false,
        title: new TextField(
          focusNode: _searchFocusNode,
          style: Theme.of(context).primaryTextTheme.title,
          decoration: InputDecoration(
            border: OutlineInputBorder(borderRadius: BorderRadius.all(Radius.circular(8.0))),
            suffixIcon: Icon(Icons.search),
            hintText: '검색',
          ),
        ),
      ),
      new SliverList(
        delegate: new SliverChildListDelegate(List.generate(
            100,
            (i) => ListTile(
                  title: Text('Scroll'),
                )).toList()),
      ),
    ],
  );
}