Padding not working on ImageButton
Solution 1:
You have to add to Your ImageButton definition
android:scaleType="fitCenter"
or other scaleType like fitXY, because by default image try to scale as much as possible and ignore padding
Solution 2:
The padding only has effect on the android:src attribute, not on the android:background.
Set the first to your button image and the latter to android:background="@android:color/transparent"