[android] Adding custom radio buttons in android

In order to hide the default radio button, I'd suggest to remove the button instead of making it transparent as all visual feedback is handled by the drawable background :

android:button="@null"

Also it would be better to use styles as there are several radio buttons :

<RadioButton style="@style/RadioButtonStyle" ... />

<style name="RadioButtonStyle" parent="@android:style/Widget.CompoundButton">
    <item name="android:background">@drawable/customButtonBackground</item>
    <item name="android:button">@null</item>
</style>

You'll need the Seslyn customButtonBackground drawable too.