app/src/main/res/drawable/custom_btn_add.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="false" android:drawable="@drawable/ic_add_circle_outline" />
<item android:state_pressed="true" android:drawable="@drawable/ic_add_circle_full" />
</selector>