New to Android development

Hi, I just started playing around with Android Studio 3.1.3 and I'm following the below tutorial. I'm at the point were I'm trying to write an Activity to a Send button. When I copied the code, it says the View symbol can't be found. I've read a bunch of posts and tried a variety of things (listed below) to no avail...any help is appreciated.

Ciao,
Christopher

Trials:
- Close then re-open the project
- File --> Invalidate Caches/Restart

Tutorial:
developer android com