FEATURE_ACTION_BAR_OVERLAY

Flag for requesting an Action Bar that overlays window content. Normally an Action Bar will sit in the space above window content, but if this feature is requested along with FEATURE_ACTION_BAR it will be layered over the window content itself. This is useful if you would like your app to have more control over how the Action Bar is displayed, such as letting application content scroll beneath an Action Bar with a transparent background or otherwise displaying a transparent/translucent Action Bar over application content.

This mode is especially useful with View.SYSTEM_UI_FLAG_FULLSCREEN, which allows you to seamlessly hide the action bar in conjunction with other screen decorations.

As of JELLY_BEAN, when an ActionBar is in this mode it will adjust the insets provided to View.fitSystemWindows(Rect) to include the content covered by the action bar, so you can do layout within that space.