Cannot resolve symbol 'Theme' in styles.xml (Android Studio)

项目中关于主题的一个问题，试过几种查阅的方法都不可以，最后在stackoverflow 找到了一个方法，试了试竟然成功了

down vote

Another solution that worked for me with Android Studio 3.1.2:

delete these from build.gradle if you have them:

'com.android.support:appcompat-v7:27.1.1''com.android.support:design:27.1.1'

then sync, then undo delete, then sync again.

就是先删除v7包，sync,然后在还原v7,在aync 问题就解决了