How to make a selector in Android Studio

Issue

While taking a course, I was instructed to make an xml selector for a Button. The course said to make a new Android xml in Eclipse, but i am using Android Studio.

Also when I custom write the code it gives me an error. It says "element selector must be declared".

Got code from here: Android: How to Make A Drawable Selector.

Does anyone know how to do this in Android Studio?

Solution

Though it is already answered in the comment,

Answered By - Dev Gurung