//取消标题
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
//取消状态栏
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);

<?xml version="1.0" encoding="utf-8"?>
<resources> 
<!-- name 是Style的名称，parent 继承那个父类样式 -->
<style name="theme_fullScreen" parent="android:Theme.Black"> 
<item name="android:windowNoTitle">true</item> <!-- 设置无标题 -->
<item name="android:windowFullscreen">?android:windowNoTitle</item> <!-- 是否填充慢屏幕，引用android:windowNoTitle 的值 -->
</style> 
</resources>

<activity android:name=".LoginActivity" android:theme="@style/theme_fullScreen"/>