Android Studio suddenly cannot resolve symbols

Question

Android Studio 0.4.2 was working fine and today I opened it and almost everything was red and the auto-completion had stopped working. I look at the imports and AS seems to

Answer 1

I tried cleaning the project and then invalidating the cache, neither of which worked. What worked for me was to comment out all my dependencies in build.gradle (app), then sync, then uncomment the dependencies again, then sync again. Bob's your uncle.