<style name="myTheme">

         <item name="android:windowNoTitle">true</item>

         <item name="android:windowFullscreen">true</item>

         <item name="android:windowBackground">@drawable/my_shapdrawable</item>

     </style>

  @Override

     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setTheme(R.style.myTheme);// 改变主题必须在setContentView之前

         setContentView(R.layout.main);

         textView = (TextView) findViewById(R.id.textView_xml);

     }