Question

How do I style an image button so that it displays as a PNG icon but on click/touch, the PNG shape gets a soft glowing edge?

Answer 1

You probably want to look at 9-patch

Basically you create a transparent png with the glow effect baked into the image, and it’ll scale the edges while keeping the corners intact and letting you place the content within a predefined area of the image.

To map your images to a button, you need a selector, which is a xml file and goes into your projects drawables. A sample grabbed from another answer looks like this

<?xml version="1.0" encoding="utf-8"?>    
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true" android:drawable="@drawable/red_button_pressed" />
    <item android:state_focused="true" android:drawable="@drawable/red_button_focus" />
    <item android:drawable="@drawable/red_button_rest" />
</selector>