cannot resolve symbol 'R' in android studio 3.3.1 : I am using android 3.3.1. I am currently taking an android development bootcamp online course on udemy. After I cloned the project from github to android studio (bitcoin-ticker), after the graddle files synchronize and project is loaded, when I open the MainActivity in java, I get R in red saying cannot resolve symbol 'R'. I didn't see a r class files in the project. So, I cleaned and built the project, android studio generated automatically the r class. I still had the cannot resolve symbol 'R' error. I moved the generated r class file to the same package where MainActivity java is with no result.
Here is a picture of what it looks. Does anyone know how can I get rid of the red R and get the project to compile?

Thanks in advance

[enter image description here][1]


  [1]: https://i.stack.imgur.com/BYlXs.png