FutureBuilder 异步数据调用

      child: new FutureBuilder<Post>(
          future: fetchPost(),
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              return new VideoPlayerUI.network(
                url: snapshot.data.url,
                title: snapshot.data.title,
              );
            } else if (snapshot.hasError) {
              return new Text("${snapshot.error}");
            }

            // By default, show a loading spinner
            return new CircularProgressIndicator();
          },
        ),