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

Go through the link and it worked for me.

1.) Choose File option from menu on left top side of android studio.

2.) Select the option : "Invalidate Cache/ Restart.." It will open an dialog.

3.) Click on the first button with option : "Invalidate and Restart"

4.) It will close the studio and restart it. Start indexing of the project.

It resolved my problem:

File -> Invalidate Cache/ Restart -> Invalidate and Restart

Source: https://www.youtube.com/watch?v=FX_gCTpqhwM