Future _deleteImageFromCache() async {
    String url = "your url";
    await CachedNetworkImage.evictFromCache(url);
  }


https://stackoverflow.com/questions/57059306/how-to-clear-cache-in-cachednetworkimage-flutter

cached_network_image

大概可能是这个插件不使用默认的cache了，用他自定义的cache清除函数