How to crop a button in android?

Question

Java

Good!
I want to make a button that looks like an icon, but even I can not cope.
1) the background is larger than the picture, although wrap_content is worth the height and width.
2) if I change the color of the backgroud to any other than the default, there is no touch animation (color change)

Answer 1

The touch animation has already been answered, but in order to have the correct dimensions, you need to look towards the 9-patch