Define and apply style on text

To define style, create a xml in res/values/ directory, The name is arbitrary. For example: mystle.xml.

/res/values/mystyle.xml

<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:android="http://schemas.android.com/apk/res/android">
    <style name="bigred_mono" parent="@android:style/TextAppearance.Medium">
        <item name="android:layout_width">fill_parent</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:textSize">30sp</item>
        <item name="android:textColor">#FF0000</item>
        <item name="android:typeface">monospace</item>
    </style>
    <style name="smallblue" parent="@android:style/TextAppearance.Medium">
        <item name="android:layout_width">fill_parent</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:textSize">10sp</item>
        <item name="android:textColor">#0000FF</item>
    </style>
</resources>

Then, you can apply the style in your layout xml.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        style="@style/bigred_mono"
        android:text="It's bigred_mono" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        style="@style/smallblue"
        android:text="It's smallblue" />

</LinearLayout>