AndroidManifest.xml

  .....

  <uses-sdk
        android:minSdkVersion="15"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

  ..... 

styles.xml

    .....

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

    .....