AAPT error: resource drawable/… not found

Question

After recently upgrading my android studio, I am not able to build my project anymore.

Every time I execute a build, I am struck with the following error:

Answer 1

In my case it was an xml selector. In the first line I had two of these (thanks to copy paste among my files):

and Android Studio didn't give any warning or something. Removing it fixed the problem but it needed a full clean build afterwards.