Flutter Dismissible Widget-从API下一篇文章的onDismissed方向

Question

我在代码中添加了Dismissible小部件，以从JSON API中消除当前帖子图像，以通过在垂直方向上向上滑动（类似于火种轻扫）在关闭后显示下一个帖子图像。我已经尝试了onDismissed：（direction）{}中的一些功能，但是不起作用。以下是我页面中包含的代码段：

class Swipe extends StatefulWidget {
  @override
  _SwipeState createState() => _SwipeState();
}

class _SwipeState extends State<Swipe> {
  var user;

  var image_url = 'http://example.com/upload/';

  void getData() async {
    var data = await getJson();

    setState(() {
      user = data['posts'];
    });
  }

  @override
  Widget build(BuildContext context) {
    getData();
    return new Scaffold(
        appBar: new AppBar(
          title: Text('News'),
          backgroundColor: Colors.indigoAccent,
        ),
        body: ListView.builder(
            itemCount: user == null ? 0 : user.length,
            itemBuilder: (context, i) {
              return new Padding(
                  padding: EdgeInsets.only(
                      left: 10.0, right: 10.0, top: 5.0, bottom: 5.0),
                  child: new Dismissible(
                    key: Key(user[i].toString()),
                    direction: DismissDirection.vertical,
                    onDismissed: (direction) {
                      setState(() {.....});
                    },
                    child: new Column(
                      children: <Widget>[
                        new Image.network(
                          image_url + user[i]['news_image'],
                          fit: BoxFit.contain,
                        ),
                        ),
                      ],
                    ),
                  ));
            }
        )
     );
  }
}