颤振：使用 RefreshIndicator 时没有刷新指示器

Question

我将 RefreshIndicator 添加到我的页面，但拉动刷新时没有可见的指示器。代码如下：

class HomePage extends StatefulWidget {
  HomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<HomePage> {

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: LocalGalleryTab(),
    );
  }
}

class LocalGalleryTab extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _LocalGalleryState();
  }
}

class _LocalGalleryState extends State<LocalGalleryTab> {
  @override
  Widget build(BuildContext context) {
    return new Container(child: new Center(
      child: new RefreshIndicator(
        child: Text("Local Gallery"),
        onRefresh: _refreshLocalGallery,
      ),
    ));
  }

  Future<Null> _refreshLocalGallery() async{
    print('refreshing stocks...');

  }
}

如何使用刷新指示器？颤振doc 没有提供太多信息。

Answer 1

使用AlwaysScrollableScrollPhysics() 将确保滚动视图始终是可滚动的，因此可以触发RefreshIndicator。

现在我想用BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics) 而不仅仅是AlwaysScrollableScrollPhysics() 滚动物理创建滚动物理。因为 BouncingScrollPhysics 适用于反弹的短列表。现在需要包含 AlwaysScrollableScrollPhysics 才能获得预期的行为。

RefreshIndicator(
    onRefresh: _onRefresh,
    child: ListView(
      padding: EdgeInsets.all(8.0),
      physics: const BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics()),
      children: _listData.map((i) {
        return ListTile(
          title: Text("Item $i"),
        );
      }).toList(),
    )
);

Answer 2

根据设计，RefreshIndicator 与 ListView 一起使用。

但如果您想将RefreshIndicator 与不可滚动小部件一起使用，您可以将小部件包装到Stack 和ListView：

RefreshIndicator(
  onRefresh: () {},
  child: Stack(
    children: <Widget>[ListView(), YOUR_CHILD_WIDGET],
  ),
),

Answer 3

您需要在RefreshIndicator 中添加滚动子项 见下面的例子

class HomePage extends StatefulWidget {
  HomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<HomePage> {

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: LocalGalleryTab(),
    );
  }
}

class LocalGalleryTab extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _LocalGalleryState();
  }
}

class _LocalGalleryState extends State<LocalGalleryTab> {
  @override
  Widget build(BuildContext context) {
    return new Container(child: new Center(
      child: new RefreshIndicator(
        child: ListView(
          children: List.generate(50,  (f) => Text("Item $f")),
        ),
        onRefresh: _refreshLocalGallery,
      ),
    ));
  }

  Future<Null> _refreshLocalGallery() async{
    print('refreshing stocks...');

  }
}