how to add a button in android?

I am new to android.

Tell me how to add a button in andro开发者_StackOverflow社区id. And when we clicks on it it has to do a activity

These two articles should help you get started:

http://developer.android.com/guide/topics/ui/ui-events.html

and

http://developer.android.com/resources/tutorials/views/hello-formstuff.html

Good Luck!

Download sample app from developer.android.com and start to play with it.