July 25,2016

Today i come to know about the styles and themes used in android.

A style resource defines the format and look for a UI. A style can be applied to an individual View (from within a layout file) or to an entire Activity or application (from within the manifest file).

Defining Styles

A style is defined in an XML resource that is separate from the XML that specifies the layout. This XML file resides under res/values/ directory of your project and will have <resources> as the root node which is mandatory for the style file. The name of the XML file is arbitrary, but it must use the .xml extension.

You can define multiple styles per file using <style> tag but each style will have its name that uniquely identifies the style. Android style attributes are set using <item> tag as shown below −

<?xml version="1.0" encoding="utf-8"?>
<resources>
   <style name="CustomFontStyle">
      <item name="android:layout_width">fill_parent</item>
      <item name="android:layout_height">wrap_content</item>
      <item name="android:capitalize">characters</item>
      <item name="android:typeface">monospace</item>
      <item name="android:textSize">12pt</item>
      <item name="android:textColor">#00FF00</item>/> 
   </style>
</resources>

Android Themes

Hope you understood the concept of Style, so now let’s try to understand what is a Theme. A theme is nothing but an Android style applied to an entire Activity or application, rather than an individual View.

Thus, when a style is applied as a theme, every View in the Activity or application will apply each style property that it supports. For example, you can apply the same CustomFontStyle style as a theme for an Activity and then all text inside that Activity will have green monospace font.

To set a theme for all the activities of your application, open the AndroidManifest.xml file and edit the <application> tag to include the android:theme attribute with the style name. For example −

<application android:theme="@style/CustomFontStyle">

But if you want a theme applied to just one Activity in your application, then add the android:theme attribute to the <activity> tag only. For example −

<activity android:theme="@style/CustomFontStyle">

There are number of default themes defined by Android which you can use directly or inherit them using parent attribute as follows −

<style name="CustomTheme" parent="android:Theme.Light">
   ...
</style>