Android Studio: Error parsing XML & URI is not registered

Question

After adding a new Activity to my project I get following error while compiling the layout

Gradle: Error parsing XML: not well-formed (invalid token)<

Answer 1

I got the same error for a long time and none of the answers I found online really helped me, or probably I wasn't looking the right way. At the end what I found out was the way I named the directory. So, I was trying to make the landscape layout for my app and named it layout_land. That kept showing me the URI is not registered error. I just had to change the directory name to layout-land.

Summary: No underscores in directory names!