protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //to remove "information bar" above the action bar
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
    //to remove the action bar (title bar)
    getSupportActionBar().hide();
}

requestWindowFeature(Window.FEATURE_NO_TITLE);

隐藏状态栏和操作栏，使你的活动全屏使用以下代码在你的活动的onResume()或onWindowFocusChanged()方法:

@Override
protected void onResume() {
    super.onResume();
    View decorView = getWindow().getDecorView();
    decorView.setSystemUiVisibility(
            View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
            | View.SYSTEM_UI_FLAG_LAYOUT_STABLE
            | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
            | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_FULLSCREEN);
}

你可在以下连结找到更多资料:

https://developer.android.com/training/system-ui/immersive#EnableFullscreen 全屏，没有导航和状态栏 如何隐藏Android手机上的软键栏?

注意:使用这个线程中提供的xml解决方案，我只能隐藏状态栏，而不能隐藏导航栏。

你的“变通”(隐藏actionBar自己)是正常的方式。但是谷歌建议当标题栏被隐藏时总是隐藏动作栏。看看这里:https://developer.android.com/training/system-ui/status.html

此主题仅适用于API 21(包含)之后。并使状态栏和导航栏都透明。

<style name="TransparentAppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
  <item name="windowActionBar">false</item>
  <item name="windowNoTitle">true</item>
  <item name="android:statusBarColor">@android:color/transparent</item>
  <item name="android:windowBackground">@android:color/transparent</item>
  <item name="android:navigationBarColor">@android:color/transparent</item>
  <item name="android:windowIsTranslucent">true</item>
  <item name="android:windowContentOverlay">@null</item>
</style>

您可以遵循以下步骤:-

AndoridMenifest.xml

<activity
            android:name=".ui.FullImageActivity"
            android:label="@string/title_activity_main"
            android:screenOrientation="landscape"
            android:theme="@style/DialogTheme">
        </activity>

Style.xml

<style name="DialogTheme" parent="android:Theme.Dialog">

    <item name="android:layout_width">fill_parent</item>
    <item name="android:layout_height">fill_parent</item>

   <!-- No backgrounds, titles or window float -->
    <item name="android:windowNoTitle">false</item>
    <item name="android:windowFullscreen">true</item>
    <item name="android:windowIsFloating">false</item>
</style>

FullImageActivity.java

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setLayout(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    setContentView(R.layout.image_view);
     }

希望对大家有所帮助，谢谢!!