CachedNetworkImage 图片缓存

CachedNetworkImage(
        imageUrl: "http://via.placeholder.com/350x150",
        placeholder: (context, url) => new CircularProgressIndicator(),
        errorWidget: (context, url, error) => new Icon(Icons.error),
     ),

原文：https://www.cnblogs.com/braveheart007/p/11038607.html