How to make android apps ?? What are requirements to make an android app???

Answer 1

knowledge of java and xml

https://www.sololearn.com/Discuss/823823/?ref=app

Answer 2

download android studio
https://developer.android.com/studio/index.html
you must have strong grip on Java, as well xml, you can design UI layouts and the screen elements they contain with xml.
if you are beginner learn basic from udacity android course...