看起来像是flutter本身的内存管理释放问题，即使在页面释放image的cache也不行。
原因是因为旧版本的flutter对GridView和ListView组件加载高分辨率图片的缓存和回收处理有问题导致内存暴涨无法自动回收，手动关掉缓存，清图片cache也不行。官方在最新master分支代码解决了这个问题，加载图片的时候内存占用没有明显波动
参考：
https://github.com/flutter/flutter/issues/32143
https://github.com/flutter/flutter/issues/28912
https://github.com/flutter/flutter/issues/19754
https://github.com/flutter/flutter/issues/20521
https://github.com/flutter/flutter/pull/42785
https://github.com/flutter/flutter/issues/28037
https://github.com/flutter/engine/pull/9329
https://github.com/flutter/flutter/issues/32286
https://github.com/flutter/engine/pull/9486
https://github.com/flutter/flutter/issues/28037
https://github.com/flutter/flutter/issues/19558
https://github.com/flutter/flutter/issues/26837#issuecomment-456675863
https://github.com/flutter/flutter/issues/28912
https://github.com/flutter/flutter/issues/21571
https://github.com/flutter/engine/pull/9486
https://github.com/alibaba/flutter_boost/issues/245
http://www.ptbird.cn/flutter-route-named-route-list-root-route.html#menu_index_10
而且问了下不会merge到1.9.1hotfixes分支。只能等最新的稳定版了，或者自己改一个版本
