<resources xmlns:android="http://schemas.android.com/apk/res/android">
  <!-- Application theme. -->
  <style name="AppTheme" parent="AppBaseTheme">
    <item name="android:windowNoTitle">true</item>
</resources>

public class MainActivity extends Activity{
  @Override
  protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    // 隐藏标题栏
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    // 隐藏状态栏
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
    WindowManager.LayoutParams.FLAG_FULLSCREEN);
    //一定要放在setContentView()之前！
    setContentView(R.layout.activity_main);
  }
}

<!-- 同时隐藏状态栏和标题栏 -->
<activity
  android:name="com.ysj.demo.MainActivity"
  android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
  android:label="@string/app_name" >
  <intent-filter>
    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.LAUNCHER" />
  </intent-filter>
</activity>