Android Module Development ---- answer interface design

After completion of the user interface design, the core is designed to answer the interface, the interface of the present technique relates to the use point comprising a database SQLite

(1) Click event options.
After completing the answer interface layout, as shown below,

when I click on the option selected, the option will set the background is red, when I chose other options, the selected option also turns red, but before before the option to become a color, this function I used to achieve selector selector

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/andro