requestWindowFeature(Window.FEATURE_NO_TITLE);
 //去掉標題欄注意這句一定要寫在setContentView()方法的前面，不然會報錯的

 <application android:icon="@drawable/icon" android:label="@string/app_name" android:theme="@android:style/Theme.NoTitleBar">

 <?xml version="1.0" encoding="UTF-8" ?>
 <resources>
 <style name="notitle">
 <item name="android:windowNoTitle">
 true
 </item>
 </style>
 </resources>

 <application android:icon="@drawable/icon" android:label="@string/app_name" android:theme="@style/notitle">

   getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

<android:theme="@android:style/Theme.NoTitleBar.Fullscreen">

 <application android:icon="@drawable/icon" android:label="@string/app_name" android:theme="@style/fullscreem">