How do you define styles in Android?

In order to define a styles that can be used as theme for your app widget or layout, define the styles as a resource in the file. The resource file can have any name but ends with .xml e.g. the resource file can be named as styles.xml in the res/values directory of your project as res/values/styles.xml

<?xml version="1.0" encoding="utf-8"?> 

<resources>

<style name="CodeFont" parent="@android:style/TextAppearance.Medium">

<item name="android:layout_width">fill_parent</item>

<item name="android:layout_height">wrap_content</item>

<item name="android:textColor">#00FF00</item>

<item name="android:typeface">monospace</item>

</style>

</resources>