Image.network加载网图报错type ‘Null‘

错误: type 'Null' is not a subtype of type 'List' in type cast

解决方案:使用异步方法,延迟刷新页面

解决效果图:

 关键代码:

        body: RefreshIndicator(
            child: Image.network(
              "http://www.devio.org/img/avatar.png",
              width: 50,
              height: 50,
            ),
            //_asyncRefresh用于实现屏幕下拉时的回调函数
            onRefresh: _asyncRefresh),



Future _asyncRefresh() async {
    await Future.delayed(Duration(milliseconds: 200));
    return null;
  }

 完整代码:

class _ImageWedgetInsState extends State {
  @override
  Widget build(BuildContext context) {
    int _currentIndex = 0;

    return MaterialApp(
      title: "网络加载图片demo",
      theme: ThemeData(primarySwatch: Colors.green),
      home: Scaffold(
        appBar: AppBar(
          title: Text("加载网络图片demo"),
          leading: GestureDetector(
            onTap: () {
              Navigator.pop(context);
            },
            child: Icon(Icons.arrow_back),
          ),
        ),

        //RefreshIndicator下拉刷新组件,想要获得下拉刷新效果必须配合列表ListView使用
        body: RefreshIndicator(
            child: Image.network(
              "http://www.devio.org/img/avatar.png",
              width: 50,
              height: 50,
            ),
            //_asyncRefresh用于实现延迟刷新页面的回调函数
            onRefresh: _asyncRefresh),
      ),
    );
  }

  Future _asyncRefresh() async {
    await Future.delayed(Duration(milliseconds: 200));
    return null;
  }
}