Themes

Para trocar o theme de um application basta mudar no manifest:

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

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

  package="com.cores"

  android:versionCode="1"

  android:versionName="1.0" >

  <uses-sdk android:minSdkVersion="7" />

  <application

      android:icon="@drawable/ic_launcher"

      android:label="@string/app_name" >

      <activity

          android:name=".Xml_coresActivity"

          android:label="@string/app_name"

          android:theme="@android:style/Theme.Dialog" >

          <intent-filter>

              <action android:name="android.intent.action.MAIN" />

              <category android:name="android.intent.category.LAUNCHER" />

          </intent-filter>

      </activity>

  </application>

</manifest>

Theme.Dialog

Theme.Translucent

Theme.Wallpaper

Theme.Light